Canopy Extinction Coefficient Research Articles

Agronomic and physiological characteristics of high yield and nitrogen use efficient varieties of rice: Comparison between two near‐isogenic lines

AbstractIncreasing the application of nitrogen fertilizer is the main approach to increase rice production, but it also brings problems of environmental pollution and increases agricultural production costs. Cultivating high‐yielding and high nitrogen use efficiency (NUE) rice varieties is an important approach to solving this problem. The rice varieties carrying dep1 (dense and erect panicle 1) have both high grain yield and high NUE. However, their plant traits have not been fully explored. In this study, two rice near‐isogenic lines carrying dep1 (NIL‐DEP1 and NIL‐dep1) were grown in paddy fields under 0, 120 and 270 kg N ha−1. We analyzed agronomic traits of panicle type, plant type, leaves and roots, and physiological traits of vascular bundles, photosynthetic rate and carbon and nitrogen transport. The results showed that the NIL‐dep1 exhibited higher grain yield and NUE than NIL‐DEP1, mainly due to the higher spikelet number per panicle, grain filling percentage and dry matter production. Compared with NIL‐DEP1, NIL‐dep1 had improved flag leaf morpho–physiological traits, including erect flag leaves, greater leaf thickness and specific leaf weight, higher root dry weight, root length, root volume and root surface area, and a better canopy structure, as reflected by a lower light interception percent and canopy extinction coefficient, leading to better photosynthetic performance and dry matter production. In addition, NIL‐dep1 exhibited better vascular bundle traits of peduncle and enhanced dry matter, stem carbon and nitrogen translocation during grain filling. In conclusion, NIL‐dep1 had high grain yield and NUE by improved agronomic and physiological traits and increasing carbon and nitrogen translocation during grain filling. These traits mentioned above could be used to select and breed high grain yield with high NUE rice varieties.

Cacao Water Use, Canopy Characteristics and Yield as Affected by Irrigation and Shade in a Rainforest Zone of Nigeria

There has been need to improve crop and water productivity considering the need for agricultural intensification in the realm of increasing water scarcity and drought in several regions of the world. Information is limited about the effects of irrigation on cacao water use (evapotranspiration) especially, during the terminal drought situation of the dry season in the rainforest agroecology of Nigeria. The effects of shade and dry season irrigation was examined on tree water use, canopy characteristics and pod and bean yields of cacao (Theobroma cacao L.). Treatments were 2 by 2 factorial combinations of irrigation intervals (5 and 10 days) and shade and no-shade (open sun) laid out in a split-plot scheme with 3 replications. Shade regimes constituted the main plots and irrigation intervals the sub-plot treatments. Irrigation water was delivered at 5-and 10-day intervals on emitter lines using gravity drip system. Irrigation combinations affected cacao canopy characteristics (leaf area index) and light integrals (photosynthetic active radiation (PAR) and canopy light attenuation (extinction coefficient, k) within the cacao field. The unshaded-irrigation had higher proportion of incident radiation (I) transmitted (Io) through the canopy (IO/I), PAR intensity, and canopy extinction coefficients (k) compared with the shaded plus irrigations at 5-and 10-day intervals. Cumulative seasonal irrigation (12119 and 8483 mm), soil moisture contents (19.6 to 13.7 %) and cacao water use (ETc: 3.8 and 3.2 mm.day-1) differed for the respective 5- and 10-day irrigation intervals. The unshaded plus 5- and 10-day irrigation intervals out-yielded the shaded-irrigation combinations for number and weights of pods and beans. Pod and bean yields were significantly different under irrigation treatments, the 5-day irrigation produced greater number and heavier pods and beans compared with the 10-day irrigation. For the shade-irrigation combinations the range of values were: weights of pods (78000 to 6000 kg/plant), beans (4.8 to 3.2 t/ha) and water productivities: Irrigation WUE: 0.45 to 0.33 mm/kg/ha) and ET WUE: 0.11 to 0.09 mm/kg/ha). The shade-irrigation strategy enhanced cacao leaf area index, water use and bean yields and ameliorated climate stress.

Alleles of high-yielding indica rice that improve root hydraulic conductance also increase flag leaf photosynthesis, biomass, and grain production of japonica rice in the paddy field

Improving net leaf photosynthetic rate ( A n ) by molecular breeding is an important research challenge in improving rice productivity. For the effective use of a locus or gene that increases A n in breeding, we must not only elucidate its roles in traits that increase A n but also evaluate its effects on phenology, leaf area, and canopy architecture and light-interception characteristics, all of which affect biomass and grain production. Alleles of the high-yielding indica rice cultivars ‘Habataki’ on chromosome (Chr.) 5 and ‘Takanari’ on Chr. 10 increase A n of rice with a japonica ‘Koshihikari’ genetic background. Here, we developed near isogenic lines (NILs) carrying these alleles (NIL5 and NIL10) and elucidated their performance in photosynthesis and in biomass and grain production in plants grown in the paddy field and pots. NIL5 and NIL10 had flag leaves with 12–13% higher A n than those of Koshihikari from full heading to ripening. Their higher A n of the flag leaf was attributable to higher stomatal conductance ( g s ). NIL5 and NIL10 had a larger whole-plant hydraulic conductance than Koshihikari owing to the increased root surface area and root hydraulic conductance. NIL5 and NIL10 produced 6–10% more biomass at harvest and 8–14% higher grain yield than Koshihikari. Their crop growth rate was higher via higher net assimilation rate (NAR) during ripening. Heading date, ripening duration, biomass at booting (or heading), leaf area index, canopy architecture and canopy extinction coefficient at ripening and harvest index did not differ between Koshihikari and either NIL. Thus, the higher NAR and the consequent higher biomass and grain production in NIL5 and NIL10 were attributed to their increased flag leaf A n . We conclude that both alleles are involved in improving root hydraulic conductance, which in turn increase flag leaf A n , biomass and grain production, and they can be used in breeding high-yielding rice. • Alleles on chromosomes 5 and 10 enhanced flag leaf photosynthesis during ripening. • The higher photosynthesis was attributed to improved root hydraulic conductance. • These alleles did not alter phenology, leaf area, or canopy extinction coefficient. • Plants carrying these alleles produced more biomass and grain. • These alleles can be used in breeding high-yielding rice.

Light Interception, Photosynthetic Performance, and Yield of Oil Palm Interspecific OxG Hybrid (Elaeis oleifera (Kunth) Cortés x Elaeis guineensis Jacq.) under Three Planting Densities.

Environmental conditions are crucial for crops’ growth, development, and productivity. One of the most important physiological factors associated with the production of crops is the use of solar radiation for the photosynthesis process, which determines the amount of assimilates available for crop growth and yield. Three age classes (4, 6, and 14 years) and three planting densities (143, 128, and 115 palms ha−1) were evaluated in a commercial interspecific Elaeis Oleifera x Elaeis guineensis hybrid Coari x La Mé. The light interception patterns and the photosynthetic performance were determined. Measurements were taken of the leaf area, the number of leaves, and incident and photosynthetically transmitted active radiation. Also, photosynthetic rates, light, and yield were measured. The canopy extinction coefficient (Kc) was estimated using the Monsi and Saeki model. Under the evaluated conditions, the average Kc value for 4-year-old palms was 0.44; for the 6-year-old group of palms, the average value was 0.40, and 0.32 for the 14-year-old palms, with coefficients of determination (R2) greater than 0.8. A pattern associated with the age of the crop was observed, where the Kc decreased in groups of adult palms. The results showed increased Kc as the planting density decreased. No statistically significant differences were observed between planting densities or ages in the light and CO2 curves regarding photosynthesis. The leaf level in which the measurement was made influenced photosynthesis. Thus, the highest values of the photosynthesis parameters were observed in leaf 17. The crop yield tended to stabilize 8 years after planting under 143 and 128 palms per hectare, but 14 years after planting, the Fresh fruit bunch (FFB) production was still growing under 115 palms per hectare. The results showed that, up to year 14 after planting, the highest cumulative yield was achieved with 115 palms per hectare. This was partly caused by a sharp decline in production observed under 128 palms per hectare, which could indicate that in the long production cycle of the OxG hybrids, the 115-palms-per-hectare planting density would result in higher cumulative FFB production. Furthermore, the results showed that the optimum planting density for the hybrids of the present study would be 120 palms ha−1, corresponding to a planting distance of 9.8 m between plants.

The mangrove blue carbon sink potential: Evidence from three net primary production assessment methods

Mangrove forests are among the highest carbon (C) sinks in the tropics and subtropics worldwide. Net primary productivity (NPP) is estimated by the permanent plot method with litterfall plus incremental growth (LG) and has great significance for the evaluation of the carbon sequestration capacity of forests. Here, we developed a new high-resolution method, sap flow investigation (SF), for the evaluation of carbon sequestration capacity. We also compared the forest carbon sequestration capacity estimated using two NPP estimation methods, stand water use using SF and light attenuation/gas exchange (LA), with traditional permanent plots using the LG method in four typical mangrove forests in the Futian Mangrove Reserve of Shenzhen City, China. The LG results showed that mangrove forests had NPPs ranging from 7.67 to 11.87 Mg C ha−1 yr−1, with species-specific differences. Among the three methods, the LG method is the most widely used, although it is costly and difficult to implement in the field. The LA results showed seasonal variation of NPP, with 4.69 g C m−2 d-1 in summer and 2.02 g C m−2 d-1 in winter. The LA method is relatively simple, but it requires a homogeneous canopy structure with a simple canopy extinction coefficient, which is suitable for mangroves with homogenous canopy structures. Although costly, the most convenient and efficient method is the SF method, which can realize continuous and high-precision dynamic NPP monitoring at the stand scale. After standardization by the LG method, the two high-resolution NPP methods could be used in mangrove forests with different time scales. For the global scale, after modification by the correction method provided in our study, the error caused by the determination method could be eliminated, which could make the global database more plentiful and accurate.

Quantitative trait loci for leaf inclination angle in rice detected using reciprocal mapping populations

• Six Takanari alleles increased leaf inclination angle at least twice in four years. • No Koshihikari alleles consistently increased leaf inclination angle. • Takanari alleles decreased the length of lamina joint cells on the adaxial side. • Takanari alleles improved light penetration into the canopy. • The effects of Takanari alleles were not enhanced by pyramiding QTLs. The improvement of canopy architecture is a feasible way to increase rice productivity. However, its genetic control in rice cultivars in the field is not well understood. The high-yielding indica cultivar Takanari has more erect leaves (a larger leaf inclination angle: LIA) during ripening, and this contributes to its higher dry matter production than that of the widely grown but less productive japonica cultivar Koshihikari. To identify quantitative trait loci (QTLs) for increasing LIA, we used reciprocal mapping populations of backcross inbred lines (131 lines in 2009 and 143 lines in 2010) and chromosome segment substitution lines (80 lines in 2011 and 2012) derived from a cross between Takanari and Koshihikari. Six Takanari alleles increased LIA at least in two of the four years, but we could not detect any such Koshihikari alleles. Five QTLs for LIA were expressed in plants with both Koshihikari and Takanari genetic backgrounds. LIA of two near isogenic lines carrying only one Takanari allele reached the level of Takanari. The Takanari alleles of the QTLs decreased the length of parenchyma cells in the lamina joint on the adaxial side in plants with the Koshihikari background, decreasing the ratio of the lamina joint length on the adaxial side to that on the abaxial side (LJ ratio) and thus increasing LIA. Three Takanari alleles increased dry matter production in plants with Koshihikari background via decreasing the canopy extinction coefficient ( k ). However, any pyramiding effects of Takanari alleles on LJ ratio, LIA, k and dry matter production were not observed.

Semi-dwarf 1 (sd1) gene enhances light penetration into the canopy through regulating leaf inclination angle in rice

Manipulating leaf inclination angle is a feasible approach to improve canopy photosynthesis and dry matter production in rice (Oryza sativa) via enhancing light penetration into the canopy. The importance of the semi-dwarf 1 (sd1) gene, a loss-of-function allele of SD1 encoding GA-20 oxidase-2 in gibberellin (GA) biosynthesis, in rice yield through improving lodging resistance is well known. However, little is known about the effects of sd1 as well as GA on leaf inclination angle. A near-isogenic line carrying the ‘Takanari’ sd1 allele in the ‘Koshihikari’ genetic background (NIL-sd1) had leaves with larger (more erect) leaf inclination angle and showed a smaller canopy extinction coefficient at the ripening stage than did ‘Koshihikari’. Furthermore, the leaf inclination angle of ‘Reimei’, an sd1 mutant in the ‘Fujiminori’ background, and of several other sd1 mutants in ‘Koshihikari’ background, was larger at the ripening stage than in parental lines, ‘Fujiminori’ and ‘Koshihikari’, respectively. The flag leaves of ‘Koshihikari’ plants treated with a GA biosynthesis inhibitor, paclobutrazol (PBZ), displayed a larger leaf inclination angle than did those of mock-treated plants during ripening. Treatment at the lamina joint of a flag leaf with exogenous GA3 or brassinolide (BL) significantly decreased leaf inclination angle. BL treatment increased the thickness of lamina joint tissue and the longitudinal cell length on the adaxial side of the marginal region of lamina joint, whereas GA3 treatment only increased the longitudinal cell length. NIL-sd1 had a lamina joint with decreased longitudinal adaxial cell length, but no difference in abaxial cell length nor tissue thickness in lamina joint cross section compared with that of ‘Koshihikari’. Thus, sd1 regulates the leaf inclination angle via a GA-based mechanism but not via BL involved in the crosstalk with GA.

Light interception and radiation use efficiency response to tridimensional uniform sowing in winter wheat

Improving radiation use efficiency (RUE) of the canopy is necessary to increase wheat (Triticum aestivum) production. Tridimensional uniform sowing (U) technology has previously been used to construct a uniformly distributed population structure that increases RUE. In this study, we used tridimensional uniform sowing to create a wheat canopy within which light was spread evenly to increase RUE. This study was done during 2014–2016 in the Shunyi District, Beijing, China. The soil type was sandy loam. Wheat was grown in two sowing patterns: (1) tridimensional uniform sowing (U); (2) conventional drilling (D). Four planting densities were used: 1.8, 2.7, 3.6, and 4.5 million plants ha−1. Several indices were measured to compare the wheat canopies: photosynthetic active radiation intercepted by the canopy (IPAR), leaf area index (LAI), leaf mass per unit area (LMA), canopy extinction coefficient (K), and RUE. In two sowing patterns, the K values decreased with increasing planting density, but the K values of U were lower than that of D. LMA and IPAR were higher for U than for D, whereas LAI was nearly the same for both sowing patterns. IPAR and LAI increased with increasing density under the same sowing pattern. However, the difference in IPAR and LAI between the 3.6 and 4.5 million plants ha−1 treatments was not significant for both sowing patterns. Therefore, LAI within the same planting density was not affected by sowing pattern. RUE was the largest for the U mode with a planting density of 3.6 million plants ha−1 treatment. For the D sowing pattern, the lowest planting density (1.8 million plants ha−1) resulted in the highest yield. Light radiation interception was minimal for the D mode with a planting density of 1.8 million plants ha−1 treatment, but the highest RUE and highest yield were observed under this condition. For the U sowing pattern, IPAR increased with increasing planting density, but yield and RUE were the highest with a planting density of 3.6 million plants ha−1. These results indicated that the optimal planting density for improving the canopy light environment differed between the sowing patterns. The effect of sowing pattern×planting density interaction on grain yield, yield components, RUE, IPAR, and LMA was significant (P<0.05). Correlation analysis indicated that there is a positive significant correlation between grain yield and RUE (r=0.880, P<0.01), LMA (r=0.613, P<0.05), and spike number (r=0.624, P<0.05). These results demonstrated that the tridimensional uniform sowing technique, particularly at a planting density of 3.6 million plants ha−1, can effectively increase light interception and utilization and unit leaf area. This leads to the production of more photosynthetic products that in turn lead to significantly increased spike number (P<0.05), kernel number, grain weight, and an overall increase in yield.

A near-isogenic rice line carrying a QTL for larger leaf inclination angle yields heavier biomass and grain

Manipulating plant architecture is a promising strategy for further improving rice production. The canopy extinction coefficient (k), the most important parameter of canopy architecture, represents the characteristics of light penetration into the canopy, and is determined mainly by the leaf inclination angle. With its erect leaves, the high-yielding indica cultivar ‘Takanari’ has a smaller k during ripening than the elite japonica cultivar ‘Koshihikari’. Using chromosome segment substitution lines derived from a cross between ‘Takanari’ and ‘Koshihikari’, we previously detected a quantitative trait locus (QTL) for leaf inclination angle on a chromosome 3. Here, we tested a near-isogenic line (NIL-3) carrying the ‘Takanari’ allele of a QTL for larger leaf inclination angle on chromosome 3, qLIA3, in the ‘Koshihikari’ genetic background for the effects of qLIA3 on k, dry matter production, and grain yield. NIL-3 had leaves with a larger inclination angle from the full heading through ripening stages and a smaller k at the ripening stage than ‘Koshihikari’. There were no differences in plant height, panicle size, heading date, leaf area index, or individual leaf photosynthesis between NIL-3 and ‘Koshihikari’. Biomass at harvest was significantly greater in NIL-3 than in ‘Koshihikari’ owing to a higher net assimilation rate during ripening, resulting in a higher grain yield. qLIA3 might incorporate a promising gene for improving rice production.

Retrieving forest canopy extinction coefficient from terrestrial and airborne lidar

Accurately retrieving the extinction coefficient (k) of foliage elements is a key step to spatially mapping the radiation regime within and under a forest canopy. The azimuthal angle of foliage elements (characterized by their normal vectors) is an important factor for improving the retrieval accuracy of k using 3-D voxels derived from lidar data. In this work, we first developed and validated an approach to retrieve k for a forest canopy by considering both inclination and azimuthal angles from terrestrial laser scanning (TLS) data. Then, we explored the feasibility of applying the proposed method to aerial laser scanning (ALS) data through four point thinning experiments for both broadleaf and coniferous trees. Our results showed that: (1) TLS-based foliage orientation could capture 86% (N=209, p<0.001) and 64% (N=78, p<0.001) of the variance in manually measured azimuthal and inclination angles, respectively for an artificial broadleaf tree; (2) the proposed lidar-based k retrieval method can be applied to both ALS- and TLS- based forest lidar data; and (3) the azimuthal angle of foliage elements is an important factor for retrieving k of a forest canopy, and both TLS and ALS platforms have differing effects on the estimates of forest k. Using this new framework, we were able to use lidar data to model the expected spatio-temporal distribution of photosynthetically active radiation within forest canopies.

Effects of Shade on Microclimate, Canopy Characteristics and Light Integrals in Dry Season Field-Grown Cocoa (Theobroma cacao L.) Seedlings

Effect of shade regimes on gradients of microclimate, canopy extent (leaf area index: LAI) and light integrals in dry season field-grown cocoa (cacao) seedlings was investigated in a rainforest zone of Nigeria. The shade regimes tested were: unshaded/open-to-sun, dense shade and moderate shade. Shade intensity affected solar radiation transmission through cacao canopy, photosynthetic active radiation (PAR) and canopy light attenuation (extinction coefficient, k). Intensity of transmitted radiation below the canopy from incident radiation was highest for open-to-sun, followed by moderate and dense shade, respectively. The temporal trend of intercepted radiation showed that intercepted radiation increased from December to May, and, the values were highest for open-to-sun, followed by moderate and dense shade. The ratio of transmitted (Io) to incident (I) radiation (IO/I) was higher for open sun. Significant differences were found between open-to-sun (unshaded) and moderate and dense shade intensity for value of canopy extinction coefficient (k). The association of growing degree days (GDD), and, total leaf number (TLN) and leaf area index (LAI), were characterized by high coefficient of determination (R2) for the respective open, dense and moderate shade treatments. Inverse of the slope of the regression of relationship between estimated thermal time (°Cdays) and corresponding total leaf number (TLN) denotes leaf appearance rate (phyllochron, in °Cdays/leaf). Rate of leaf appearance was faster in open sun compared with to that in moderate or dense shade intensity. Characteristics of the cacao canopy development were measured by leaf area index (LAI), a parameter which affects the intercepted photosynthetic active radiation (PAR). Higher LAI was obtained in no shade (open sun) compared to that in moderate or dense shade treatments. Unshaded plants had a higher radiation use efficiency (RUE) and RUE values were significantly higher compared to the other two treatments. Low light intensity and LAI for under-storey cacao had negative implications for growth and biomass development. Air temperatures within the cacao field were highest for open sun cacao, followed by moderate and dense shade, respectively; the values increased from December to April, with peak values seen in April.

Atmospheric carbon dioxide enrichment induced modifications in canopy radiation utilization, growth and yield of chickpea [Cicer arietinum L.)

Open top chamber experiments were conducted to study the response of chickpea crop (cv. Pusa-1105) to atmospheric CO2 enrichment at 580±20ppm, in terms of radiation interception and use efficiency, biophysical parameters and yield components. The ambient (control) was kept at 384±13ppm. A significant increase in leaf area index was recorded through CO2 enrichment, while no change in fractional intercepted photosynthetically active radiation was observed. This might be due to significant reduction (18.5%) in the canopy extinction coefficient. A 24% increase in radiation use efficiency resulted in 27.3% higher crop biomass. The specific leaf nitrogen content was higher although there was a reduction in specific leaf area, indicating increase in laminar thickness under enriched atmospheric CO2 environment. Greater water soluble carbohydrate concentration in leaves suggests greater C assimilation under enriched atmospheric CO2, with wide leaf C:N ratio at 50% flowering. There was no significant change in harvest index, but larger C:N in grains indicated reduction in the quality of grains. We conclude that a significant increase in chickpea productivity under enriched CO2 will occur, although at the cost of reduction in nutritional quality of the produce.

Sorghum dwarfing genes can affect radiation capture and radiation use efficiency

Presence of the dw3 sorghum dwarfing gene had negative effects on grain yield in some genetic backgrounds and environments. In a previous study we showed that this was due to a significant reduction in shoot biomass (mainly via reduced stem mass), which in turn negatively affected grain size. The current study examines whether shoot biomass was reduced via effects of dw3 on traits associated with resource capture, such as leaf area index (LAI), light interception (LI), and canopy extinction coefficient (k) or with resource use efficiency, such as radiation use efficiency (RUE). Three pairs of near-isogenic sorghum lines differing only in the presence or absence of the dwarfing allele dw3 (3-dwarfs vs 2-dwarfs) were grown in large field plots. Biomass accumulation and LI were measured for individual canopy layers to examine canopy characteristics of tall and short types. Similar to the previously reported effects on grain yield, the effects of dw3 on RUE, LI and k varied among genetic backgrounds and environments. Interactions between dw3 and genetic background, but also interactions with environment are likely to have modulated the extent to which RUE, LI, or k contributed to biomass differences between tall and short sorghum.

Integrating terrestrial and airborne lidar to calibrate a 3D canopy model of effective leaf area index

Terrestrial laser scanning (TLS) with the Echidna Validation Instrument (EVI) provides an effective and accurate method for calibrating multiple-return airborne laser scanning (ALS) point cloud distributions to map effective leaf area index (LAIe) and foliage profile within a 1-km diameter test site of mature eucalyptus forest at the Tumbarumba research site, New South Wales, Australia. Plot-based TLS foliage profiles are used as training datasets for the derivation of a scaling function applied to calibrate effective leaf area index (LAIe) from a coincident ALS point cloud. The results of this study show that: a) the mean proportion of the total number of returns within 11.3m radius of the TLS scan station was 64%. Increasing the radius decreased the level of detail due to occlusion; b) the relationship between TLS LAIe profile and ALS foliage percentile distribution (PD) using all, primary and secondary returns are not linearly related; and c) regressions between TLS LAIe profile and ALS PD, demonstrate better correspondence using a 5th order polynomial applied to all returns (r2=0.95; SE=0.09m2m−2) than aquasi-physically-based Weibull scaling function. The calibration routine was applied to ALS data within a GIS environment to create a 500m radius 3D map of LAIe. This localised 3D calibration of LAIe was then used as the basis to calculate the overhead canopy extinction coefficient parameter (k), and thereby facilitate upscaling of spatial LAIe estimates to larger domains using a Beer Lambert Law assumption.

Cotton radiation use efficiency response to plant growth regulators

SUMMARYPlant growth regulators are widely used in cotton production to improve crop management. Previous research has demonstrated changes in crop growth, dry matter (DM) partitioning and lint yield of cotton after the application of plant growth regulators. However, no reports are available demonstrating the effect of plant growth regulators on light interception and radiation use efficiency (RUE). Field studies were conducted in Fayetteville, Arkansas, USA in 2006 and 2007. RUE was estimated for the period between the pinhead square stage (PHS) of growth and 3 weeks after first flower (FF+3) from plots receiving three applications of the nitrophenolate and mepiquat chloride with Bacillus cereus plant growth regulators (Chaperone™) at 7·19 g a.i./ha and Pix Plus® at 41·94 g a.i./ha compared with an untreated control. No differences between the Chaperone treatment and the untreated control were found in the present study. However, Pix Plus significantly reduced plant height (both 2006 and 2007) and leaf area (2007 only), and altered the canopy structure of the crop as recorded by increased values of canopy extinction coefficient. Although DM accumulation was found not to be affected by plant growth regulator treatments, RUE was significantly increased after Pix Plus application, by 33·2%. RUE was increased because less light was intercepted by the Pix Plus treatment for the same biomass production, and this is probably a result of changes in photosynthetic capacity of the leaves and changes in light distribution throughout the canopy.

Physiological determinants of high yielding ultra-narrow row cotton: Canopy development and radiation use efficiency

Ultra-narrow row cotton (UNR, with rows spaced less than 40cm apart) has long been proposed to have the potential to increase yields while reducing the time to crop maturity. Investigations have shown that biomass accumulation in high-input, high yielding UNR (25cm spaced rows with yields greater than 1800kglintha−1) cotton is similar to conventionally spaced rows (100cm) despite a three-fold increase in plant density, indicating a limitation on individual plant growth. This study investigates whether the increased plant density in UNR crops (36plantsm−2) leads to differences in canopy development, radiation use efficiency (RUE) and light interception contributing to plant growth limitations. Three experiments over three years compared UNR treatments to conventionally spaced treatments in high-input production systems and found that early canopy development (leaf area index LAI) and consequently early interception was higher in the UNR crops in two of the three experiments. This resulted in a 17% higher seasonal canopy extinction coefficient (k) in UNR crops over the season. However, seasonal RUE of the UNR crop was 19% lower as increases in light interception were not accompanied by increased total dry matter. Light distribution through the canopy was poorer (higher k) in the UNR crop and LAI continued to increase in the UNR crop after maximum light interception was reached, which combined with a lower leaf nitrogen concentration may have reduced the photosynthetic efficiency of the UNR crop. We conclude that differences in canopy light interception and the efficiency of conversion of light to biomass were the primary factors responsible for differences in the pattern of biomass accumulation between UNR and conventionally spaced cotton.

&lt;b&gt;KOEFISIEN PEMADAMAN TAJUK DAN EFISIENSI PENGGUNAAN RADIASI SURYA PADA TANAMAN KENTANG (&lt;i&gt;Solanum tuberosum&lt;/i&gt; L.) VARIETAS GRANOLA DI GALUDRA, CIANJUR, JAWA BARAT&lt;/b&gt;&lt;br&gt;&lt;i&gt;CANOPY EXTINCTION COEFFICIENT AND SOLAR RADIATION USE EFFICIENCY...&lt;/i&gt;

&lt;div&gt;Important climatic factor affecting growth of potato crop other than temperature is the availability of solar energi. Growth of the crop can be predicted from the amount of intercepted solar radiation by crop canopy, however, climatological station only measures incoming solar radiation above crop canopy (Qo). This experiment aims to derive parameter of canopy extinction coefficient (k) that is required to calculate intercepted radiation based on Qo; and parameter of radiation-use efficiency (ε) to calculate crop biomass based on that intercepted radiation. This research found the value of k increasing from k=0.15 to k=0.50 associated with increasing LAI from 0.98 to 1.98. Solar radiation use efficiencies that were calculated based on above-ground biomass (AGB) and total biomass (AGB+tuber) are respectly ε&lt;/div&gt;&lt;div&gt;and ε&lt;/div&gt;&lt;div&gt;Total&lt;/div&gt;&lt;div&gt;=4,49 g MJ&lt;/div&gt;&lt;div&gt;-1&lt;/div&gt;&lt;div&gt;. Important climatic factor affecting growth of potato crop other than temperature is the availability of solar energi. Growth of the crop can be predicted from the amount of intercepted solar radiation by crop canopy, however, climatological station only measures incoming solar radiation above crop canopy (Qo). This experiment aims to derive parameter of canopy extinction coefficient (k) that is required to calculate intercepted radiation based on Qo; and parameter of radiation-use efficiency (ε) to calculate crop biomass based on that intercepted radiation. This research found the value of k increasing from k=0.15 to k=0.50 associated with increasing LAI from 0.98 to 1.98. Solar radiation use efficiencies that were calculated based on above-ground biomass (AGB) and total biomass (AGB+tuber) are respectly εand εTotal=4,49 g MJ-1. &lt;/div&gt;

Radiation interception and radiation use efficiency of three grain legumes under water deficit conditions in a semi-arid environment

Grain legumes are the main source of protein for subsistence farmers in the semi-arid tropical regions where production is limited by many biotic and abiotic stresses. Knowledge of resource capture by crop species can be one of the options in improving the productivity of crops in this environment. A study was conducted on three grain legume species, viz. common bean ( Phaseolus vulgaris L.), chickpea ( Cicer arietinum L.) and cowpea ( Vigna unguiculata L.) to study their radiation interception, radiation use efficiency (RUE) and seed yield under three water regimes in a semi-arid region of Ethiopia in two seasons. The water regimes were well-watered control (C), mid-season/flowering and pod setting period water deficit (MS) and late season/pod filling period water deficit (LS). It was found that dry matter production was highly associated with the fraction of photosynthetically active radiation (PAR) intercepted ( F, r = 0.83 * to 0.96 **), which in turn is positively correlated with LAI ( r = 0.78 * to 0.98 *) across all species and water regimes. The lowest values of F, RUE, canopy extinction coefficient ( K), seed yield and harvest index (HI) were recorded in the MS treatment. The reduction in RUE due to MS was 39, 30 and 29% and due to the LS was 18, 19 and 17% for beans, chickpea and cowpea, respectively. RUE was more sensitive to early stage than late stage reproductive water deficit in beans and chickpea while it was not significantly affected by any of the stress treatments in cowpea. RUE was positively significantly correlated with seed yield ( r = 0.85 ** to 0.89 **) and HI ( r = 0.72 * to 0.88 **) over the two seasons. It is concluded that attainment of high LAI that reduces soil water evaporation, intercepts and converts radiation into dry matter efficiently, and partitioning of the dry matter to the seed is the major requirement of a high seed yield in grain legumes in semi-arid environments.

Radiation and water use efficiencies of greenhouse zucchini squash in relation to different climate parameters

In the Mediterranean region, zucchini squash ( Cucurbita pepo L.) is widely grown under unheated greenhouse conditions for off-season production. Climatic conditions affecting both radiation and water use are mainly determined by the planting dates. Elucidating the relationship between the radiation and the water use with climate variables is important for the quantification of crop productivity and for improving water use efficiency (WUE) and radiation use efficiency (RUE). The influence of seasonal fluctuations (spring–summer and summer–fall) resulting from two planting dates (28 March and 6 September) on growth, radiation and water use efficiencies was investigated in zucchini plants cultivated hydroponically in a unheated greenhouse located at Viterbo, central Italy. Plants grown in the spring–summer season exhibited a higher maximum value of total, leaf, stem, fruit dry matter and leaf area index (971, 460, 91, 422 g m −2 and 5.1, respectively) than those grown during the summer–fall season (672, 306, 58, 311 g m −2 and 2.7, respectively). The marketable fresh yield in the spring–summer was higher than the summer–fall (6.2 versus 4.7 kg m −2). The canopy extinction coefficient was empirically determined as 0.72 for the light interception. The crop coefficient ( K c) during the spring–summer period ranged from 0.10 to 1.15, while for the summer–fall season the K c ranged from 0.12 to 0.80. Before harvest initiation, the transpiration rates, RUE and water use efficiency calculated on above dry weight basis (WUE b) were similar between growing seasons (average 0.51 L m −2 day −1, 2.07 g MJ −1 and 2.92 g kg −1, respectively), while after harvest initiation, summer–fall season showed a lower transpiration rate (0.97 versus 2.60 L m −2 day −1) and a higher RUE (4.17 versus 2.46 g MJ −1) and WUE b (4.02 versus 2.73 g kg −1) in comparison to the spring–summer season. Water use efficiency on fresh fruit yield basis (WUE y) was also higher in summer–fall season compared to spring–summer season (50.5 versus 31.5 g kg −1). The variability in RUE and WUE b was associated with, daily mean solar radiation ( R s), daily mean air temperature ( T a) and daily mean vapour pressure deficit (VPD). In both growing phases, negative exponential relationships were evident by plotting the RUE, and WUE b against climatic variables ( R s, T a and VPD). R s, T a and VPD were greatly higher in the spring–summer season, which influences RUE and WUE b negatively. These results may be applied in greenhouse climate control and management decisions. In our case the use of light selective and movable screen may improve substantially water use efficiency of warm season crops in Mediterranean areas, where water supplies are limited.

Productivity and light use efficiency of perennial ryegrass with contrasting water and nitrogen supplies

Light use efficiency (LUE) is one of the most useful parameters for estimating crop productivity. LUE relates dry matter (DM) productivity to solar radiation received on the canopy in a region. The aim of this research was to determine LUE and productivity of ryegrass ( Lolium perenne L.) cv. Liprenta under different water and nitrogen (N) levels. Two separate experiments, one in 1994 (Experiment I) and other in 1995 (Experiment II), were carried out at the Institute of Plant Production, University Bonn, Germany. Two water (low versus high) and two N (low versus high) levels were supplied to plants during the growth seasons. All observations were plotted against a thermal scale. Plant DM was significantly higher ( P<0.05) under both sufficient water and N supply but treatment interaction was found significant for DM production during the crop re-growth. Maximum DM was reached in about 700 growing degree days (GDDs). Sufficient water with higher N supply out yielded the other treatments for DM, tiller number per plant and leaf number per plant throughout sampling. Differences were more pronounced in the field (Experiment II) than in the pot trial (Experiment I). Higher DM production of the high water supply treatment was not only due to more tillers and leaves but also due to longer and wider blades that enlarged the leaf area as well as mass of the individual plant leaves. Insufficient water supply to ryegrass was found more critical than insufficient N supply. The adverse effect of insufficient water and N supply to plants decreased both the individual leaf area as well as the whole canopy leaf area index (LAI). The canopy light interception rose sharply with increasing LAI, reached the maximum at canopy closure and remained at plateau with further LAI development during the crop growth. Canopy extinction coefficient k was empirically determined as 0.86 for light interception efficiency of the ryegrass. LUE, calculated as the slope of the regression of total DM (roots+shoot) and accumulated PAR intercepted, was observed as 2.01 (N 1W 1), 2.82 (N 2W 1), 3.34 (N 1W 2) and 4.24 (N 2W 2) g DM MJ −1 PAR for Experiment I and 1.22 (N 1W 1), 2.01 (N 2W 1), 3.18 (N 1W 2) and 3.24 (N 2W 2) g DM MJ −1 PAR for Experiment II. The average LUE under sufficient water was almost double than that of the insufficient water treatment both under pot and field conditions. However, the effect of N treatments was far lower in intercepting light than the effect of water treatments both in pot and field conditions on ryegrass vegetative growth.