Higher Leaf Area Duration Research Articles

Delaying panicle nitrogen application to emergence of 3rd leaf from flag leaf increases the grain-filling ability and yield of large-panicle rice by increasing stem nonstructural carbohydrates at heading

The reserve of stem nonstructural carbohydrates (NSC) at heading can enhance the sink strength and improve the grain-filling ability of large-panicle rice, which is beneficial to realizing its high-yield potential. Delaying panicle nitrogen (N) application is expected to increase stem NSC accumulation, but the relevant technical parameters and their impact on the yield of large-panicle rice remain unclear. Two-year field experiments were conducted in 2021 and 2022 with two large-panicle rice cultivars (HLY280 and YLY228) and five panicle N treatments: panicle N application at emergence of 4th leaf from flag leaf (TL4), 3rd leaf from flag leaf (TL3), 2nd leaf from flag leaf (TL2), flag leaf (TL1), and no panicle N application (CK) as the control, to study the effect of different panicle N treatments on the accumulation and translocation of stem NSC, as well as their impact on rice yield and its components. The results showed that the panicle N treatments significantly influenced rice yield. Among the panicle N application treatments, TL3 showed the highest yield for both cultivars over two years. Compared with TL4, TL3 significantly increased the percentage of filled grains and grain weight while maintaining a similar number of spikelets per panicle, which increased the yield of HLY280 and YLY228 by 10.1–13.6% and 12.4–12.7%, respectively. Among the panicle N application treatments, TL3 significantly increased the translocation of stem mass (net output of stem mass) and stem NSC (∆NSC) from heading to 15 days after heading (DAH), which led to the highest dry matter accumulation during the initiation of grain filling from heading to 15 DAH. The higher ∆NSC of TL3 was mainly due to the higher stem NSC at heading, which was contributed by the higher stem NSC accumulation from 5 days before heading (DBH) to heading. Additionally, the higher stem NSC accumulation under TL3 from 5 DBH to heading was significantly positively correlated with the higher leaf area duration (LAD) in this period. These results suggest that delaying panicle N application to TL3 can significantly increase the yield of large-panicle rice compared with TL4 by increasing the percentage of filled grains and grain weight, which is the result of increased stem NSC accumulation.

Leaf Area Duration and Crop Radiation Use Efficiency Determine Biomass Yield of Lignocellulosic Perennial Grasses under Different Soil Water Content

The aim of the present work was to assess the leaf area duration (LAD) and the radiation use efficiency (RUE) of six warm-season perennial biomass grasses (PBGs) in a two-year field trial in the semiarid Mediterranean climate under different soil water availability. Two ecotypes of giant reed (Arundo donax L., ARCT and ARMO), one ecotype of African fodder cane (Saccharum spontaneum L. subsp. aegyptiacum (Willd.) Hack., SAC) and three hybrids of Miscanthus (the commercial M. × giganteus J.M. Greef, Deuter ex Hodk., Renvoize, M × G, and two new seed-based hybrids, GNT9 and GNT10) were compared under three levels of soil water availability: rainfed, 50% and 100% of maximum crop evapotranspiration (ETm) restoration. The determination of RUE of perennial plants is controversial and has led to contrasting results in past studies. In the present work, LAD and RUE differed among crops and irrigation regimes, being positively affected by supplemental water inputs. SAC, ARCT and ARMO showed both high LAD and RUE, which determined the high biomass yield than both the commercial M × G and the improved Miscanthus hybrids GNT9 and GNT10. RUE was particularly high and less affected by soil water availability during the mid-season, while the effect of irrigation and the differences among the genotypes were larger during the late season. Adequate biomass yield can be achieved by sub-optimal soil water availability, thus reducing the water footprint and increasing the sustainability of these biomass perennial grasses selected for the Mediterranean climate.

Application of insect-proof nets in pesticide-free rice creates an altered microclimate and differential agronomic performance.

BackgroundInsect-proof nets are commonly used in crop production and scientific research because of their environmental, economic, and agronomic benefits. However, insect-proof nets can unintentionally alter the microclimate inside the screenhouse and therefore greatly affect plant growth and yield. To examine the microclimate and agronomic performance of pesticide-free rice under insect-proof nets, two-year field experiments were carried out in 2011 and 2012.MethodsIn the present study, the experiment was conducted by using a split-plot design considering the cultivation environment (open field cultivation (OFC) and insect-proof nets cultivation (IPNC)) as the main plot and the varieties as the subplot (Suxiangjing3 and Nanjing44).ResultsIPNC significantly reduced the air speed and solar radiation, and slightly increased the daytime soil temperature, daytime air temperature, and nighttime relative humidity. By contrast, the nighttime soil temperature, nighttime air temperature, and daytime relative humidity were relatively unaffected. The grain yield of both rice cultivars decreased significantly under IPNC, which was largely attributed to the reduced panicle number. The reduced panicle number was largely associated with the decreased maximum tiller number, which was positively correlated with the tillering rate, time of tillering onset, and tillering cessation for both rice cultivars under IPNC. In addition, dry matter accumulation significantly decreased for both rice cultivars under IPNC, which was mainly caused by the decreased leaf area duration resulting from the reduced leaf area index. By contrast, the mean net assimilation rate was relatively unaffected by IPNC.DiscussionInsect-proof nets altered the microclimate in comparison with OFC by reducing the air speed and changing the radiation regime, which significantly affected dry matter production and yield of both japonica rice cultivars. Our results indicated that cultivation measures that could increase the tillering rate and the maximum tiller number under IPNC would lead to a significant increase in panicle number, ultimately increasing grain yield. In addition, maintaining a high leaf area duration by increasing the leaf area index would be important to compensate for the dry matter accumulation losses under IPNC. These findings are critical to provide a theoretical basis for improving agronomic performance of pesticide-free rice under IPNC.

Comparison of agronomic performance between inter-sub-specific hybrid and inbred japonica rice under different mechanical transplanting methods

Mechanical transplanting has been applied to rice cultivation to save labor costs and ease labor shortages in Asian countries, especially in China. However, little information is available related to the characteristics of agronomic performance when comparing inter-sub-specific hybrid rice (IHR) and inbred japonica rice (IJR) under mechanical transplanting method. In 2013 and 2014, field experiments were conducted using IHR (Yongyou 2640) and IJR (Wuyunjing 24) under two cultivation patterns, that is, pot seedlings mechanically transplanted (PS) and carpet seedlings mechanically transplanted (CS). Grain yield, yield components, leaf area index (LAI), leaf area duration (LAD), aboveground biomass, crop growth rate (CGR), nitrogen (N) uptake, and N accumulation were investigated. When compared with CS, PS displayed significantly increased grain yield for both varieties because the larger sink size allowed higher N accumulation from panicle initiation to maturity. Moreover, total aboveground biomass under PS increased significantly compared with that under CS; that is, higher photosynthetic productivity resulted from a greater LAI and higher LAD during the grain filling stage. Higher N absorption capacity in the middle and late growth periods resulted in significantly enhanced total N uptake under PS. When compared with IJR for both treatments, IHR generated 75.2% more grain yield. However, the characteristics creating high yield of IHR were different from those of IJR. Greater aboveground biomass production as well as higher N uptake and accumulation created higher grain yield in IHR than in IJR. These results suggest higher yield could be achieved using PS with IHR, attributing to exploit both yield superiority and productive potential.

Comparison of yield traits in rice among three mechanized planting methods in a rice-wheat rotation system

Understanding the differences in yield traits of rice among pothole seedling of mechanical transplanting (PSMT), carpet seedling of mechanical transplanting (CSMT) and mechanical direct seeding (MDS) is of great importance not only for rice scientists but also for rice farmers to develop a high-yield production system under mechanical conditions in a rice-wheat rotation system. However, such traits are yet to be studied among rice varieties of japonica-indica hybrid rice (JIHR), japonica conventional rice (JCR) and indica hybrid rice (IHR). Field experiments were conducted in 2014 and 2015, where six cultivars of the three rice types JIHR, JCR and IHR were grown individually with PSMT, CSMT and MDS methods, under respective managements for each method to achieve the maximum attainable yield. Results showed that (i) the PSMT significantly increased grain yield of JIHR by 22.0 and 7.1%, of JCR by 15.6 and 3.7% and of IHR by 22.5 and 7.4%, compared to MDS and CSMT on average across the two years, respectively. The highest yield was produced by the combination of JIHR and PSMT; (ii) high yield under PSMT was mainly attributed to large sink capacity and high-efficient dry matter accumulation. With sufficient panicles per hectare, the increase of spikelet number per panicle, especially the increase in spikelet number of the secondary rachis-branches was determined to be the optimal approach for developing a large sink capacity for rice under PSMT. The optimal tillers development, large leaf area index at heading stage, and high leaf area duration, crop growth rate and net assimilation rate during grain-filling phase could be the cause of sufficient dry matter accumulation for rice under PSMT; (iii) moreover, the PSMT favored plant growth as well as enriched the stems plus sheaths during grain-filling phase, as compared with CSMT and MDS. These results suggest that PSMT may be an alternative approach to increasing grain yield in a rice-wheat rotation system in the lower reaches of the Yangtze River in China.

Impact of water deficit stress on biomass production of different gladiolus cultivars under rainfed condition

Among the environmental stresses, water deficit stress was recognized to be one of the most adverse factors for plant growth and productivity. The study aimed to comparatively evaluate impact of water deficit stress on biomass of seven cultivars of gladiolus in terms of leaf area duration and net assimilation rate under rainfed conditions in northeastern region of India. Also, productions in terms of marketable spikes were compared. The parameters were measured using standard procedures. Comparatively higher leaf area duration (116 days) and net assimilation rate were found in cultivars Aarti (116 days and1.62 gcm-2day-1x10-3 respectively) and Suchitra (98.0 days and 1.10 gcm-2day-1x10-3) which account for their higher biomass production with larger spike size with good numbers of flowers. The highest marketable spikes (71111.11 spikes ha-1) was found in cultivar Aarti followed by Suchitra (68148.14 spikes ha-1) which might be due to its comparatively higher biomass production and less deviation, during stress condition, from normal characteristics. The tolerant cultivars are those that can adapt to the change without much change in their normal growth. And the responses of those species are commercially acceptable that promote adaptation without compromising much with the plant growth and crop production.

Yield comparison between dry seeded and transplanted rice in southern China

Field experiments were conducted at the Experimental Farm of Guangxi University, Guangxi province, southern China in early and late rice-growing seasons in 2012 to compare grain yield and yield attributes between dry seeded and transplanted rice. A hybrid rice cultivar Guiliangyou 2 was grown under dry seeding (DS) and dry transplanting (DT) in each season. Grain yield, yield components, tillering process, biomass production, growth duration, crop growth rate (CGR), leaf area index (LAI), leaf area duration (LAD) and net assimilation rate (NAR) were determined for each establishment method. DS produced higher and equal grain yield than DT in early and late seasons, respectively. The higher grain yield under DS in early season was attributed to improvement in both sink and source. For source, DS had significantly higher panicles/m2 than DT, which resulted in larger sink size (spikelets/m2). High tillering capacity was responsible for high panicles/m2 under DS. For the source, DS produced significantly higher biomass than DT during reproductive and grain-filling phases. High CGR was responsible for high biomass production under DS. High CGR under DS was attributed to high LAI, LAD and NAR during reproductive phase and to high LAI and LAD during grain-filling stage. No yield superiority observed under DS in late season might be associated with temperature. Mean temperature was lower in late season than in early season by 5.8°C during grain-filling phase. Our results suggest that multi-year and multi-location field experiments should be conducted in future to determine the yield stability of dry seeded rice.

Net ecosystem carbon exchange in three contrasting Mediterranean ecosystems – the effect of drought

Abstract. Droughts reduce gross primary production (GPP) and ecosystem respiration (Reco), contributing to most of the inter-annual variability in terrestrial carbon sequestration. In seasonally dry climates (Mediterranean), droughts result from reductions in annual rainfall and changes in rain seasonality. We compared carbon fluxes measured by the eddy covariance technique in three contrasting ecosystems in southern Portugal: an evergreen oak woodland (savannah-like) with ca.~21% tree crown cover, a grassland dominated by herbaceous annuals and a coppiced short-rotation eucalyptus plantation. During the experimental period (2003–2006) the eucalyptus plantation was always the strongest sink for carbon: net ecosystem exchange rate (NEE) between −861 and −399 g C m−2 year−1. The oak woodland and the grassland were much weaker sinks for carbon: NEE varied in the oak woodland between −140 and −28 g C m−2 year−1 and in the grassland between −190 and +49 g C m−2 year−1. The eucalyptus stand had higher GPP and a lower proportion of GPP spent in respiration than the other systems. The higher GPP resulted from high leaf area duration (LAD), as a surrogate for the photosynthetic photon flux density absorbed by the canopy. The eucalyptus had also higher rain use efficiency (GPP per unit of rain volume) and light use efficiency (the daily GPP per unit incident photosynthetic photon flux density) than the other two ecosystems. The effects of a severe drought could be evaluated during the hydrological-year (i.e., from October to September) of 2004–2005. Between October 2004 and June 2005 the precipitation was only 40% of the long-term average. In 2004–2005 all ecosystems had GPP lower than in wetter years and carbon sequestration was strongly restricted (less negative NEE). The grassland was a net source of carbon dioxide (+49 g C m−2 year−1). In the oak woodland a large proportion of GPP resulted from carbon assimilated by its annual vegetation component, which was strongly affected by the shortage of rain in winter. Overall, severe drought affected more GPP than Reco leading to the deterioration of NEE. Although the rain-use efficiency of the eucalyptus plantation increased in the dry year, this was not the case of evergreen oak woodland, which rain-use efficiency was not influenced by drought. Recovery after drought alleviation, i.e., beginning with heavy rain in October 2005, was fully accomplished in 2006 in the oak woodland and grassland, but slow in the eucalyptus plantation.

Effects of seed rates and plant populations on canopy dynamics and yield in the greater yam ( Dioscorea alata L.)

Four seed rates (1, 3, 5, and 7 t ha −1) and four plant populations (20, 45, 70, and 95×10 3 plants ha −1) of the ‘6322’ accession of greater yam were combined in a two factorial experiment. Measurement of LAI showed that canopy growth progressed proportionally with the seed rate. Canopy growth was not significantly influenced by plant population. A better distribution of small plants derived from higher populations most likely compensated for the higher growth rates of less densely distributed plants derived from low populations. Higher LAI caused by higher seed rates (larger setts) resulted in higher leaf area duration (LAD) and light interception (Li) throughout the growth cycle. The seed rate also strongly affected the yield components, whereas the effect of plant population was only significant for the commercial tuber yield and the number of non-commercial tubers. Nevertheless, a clear maximum among the yield components was only found for the number of commercial tubers. A ridge analysis was carried out to identify possible optima for combinations of the other variables. Commercial tuber yield tended to increase asymptotically with increasing sett size. For total yield, however, tuber production was a function of seed rate and did not respond to plant population, except at the lowest seed rate. The product of plant density and number of stems per plant should be the variable used to explain intercepted radiation in yams. Therefore, the effect of secondary spires on yam canopy dynamics rather than the plant population effect alone requires further study.

Influence of sowing date and irrigation on the growth and yield of pinto beans (Phaseolus vulgaris) in a sub-humid temperate environment

The growth and yield of pinto beans (Phaseolus vulgaris L.) cv. Othello in response to a total of six sowing dates (from October to December) and irrigation was examined over two seasons in Canterbury, New Zealand. In 1994/95, two irrigation treatments (nil and full) were combined with two sowing dates (27 October and 24 November). In 1995/96, Othello was examined under two irrigation treatments (nil and full) and four sowing dates (1 November, 15 November, 29 November and 13 December). The total rainfall for the two seasons was 50% and 60% of the long-term average, respectively. The mean temperatures for the seasons were similar to the long-term average. Both irrigation and sowing date had a marked effect on growth and seed yield. Averaged over both seasons, seed yield for fully irrigated crops was 337 g/m2, c. 50% higher than the yield of unirrigated crops. The irrigated crops yielded more than the unirrigated crops because they attained greater canopy closure, intercepting 84–95% of incident radiation. They also had on the average 47% higher leaf area duration (LAD), 72% higher maximum leaf area index (LAI) and greater utilization coefficient. The mid- to late November-sown crops yielded more than the late October to early November and December-sown crops because the leaf area of the former increased most rapidly, achieved a higher maximum LAI and LAD and consequently intercepted more photosynthetically active radiation (PAR). They also had faster pod growth rates and 26% of stored assimilates contributed to pod growth compared with 13% in late October to early November and 5% in December-sown crops. The results showed that pinto beans can grow and yield well in Canterbury, and that a yield advantage could be obtained when sown in mid- to late November and with irrigation.

Leaf Area Duration of Oat at High Latitudes

AbstractContribution of leaf area duration (LAD) to grain yield during the short growing season characteristic of northern latitudes may differ from the marked impact it has at lower latitudes. Three experiments (exps) were carried out at Viikki Experimental Farm, University of Helsinki, Finland (60° 13′N) to compare associations between main shoot and tiller LAD with grain yield, yield components and morpho‐physiological traits characterizing plant stand structure. This was done using correlation analysis and principal component analysis (PCA) for data from trials conducted during 1993–1995. Exp I included three N fertilizer rates (80, 120, 160 kg N ha−1), three seeding rates (250, 500, and 750 seeds m−2), and tall, moderate, semi‐dwarf, and dwarf oat lines. Exp II incorporated two N fertilizer rates (80 and 120 kg ha−1), three seeding rates (400, 600, and 800 seeds m−2), and naked and hulled oat lines, and exp III, foliar applications of plant growth regulators [control, chlormequat chloride (CCC), and ethephon], and dwarf, naked, and conventional oat lines. LAD for main shoots and tillers [calculated as ∫ LAI d T, where T is cumulated degree days from seedling emergence to yellow ripening (dd °C)] and 12 morpho‐physiological traits were measured. Oat was not able to benefit from high main shoot LAD if drought occurred at grain‐fill, but in the absence of severe drought or if it occurred at pre‐anthesis, high LAD favoured yield formation. Tiller LAD had a negative impact, if any, on grain yield in cases of an inverse relationship between tiller LAD and yield components on main shoots was recorded. Use of low seeding rates resulted in improved ability of total LAD to contribute to dry‐matter production, but was not associated with grain yield. Low seeding rates enhanced formation of high tiller LAD, which was not able to compensate for grain yield reduction caused by fewer main shoots. Foliar application of CCC and ethephon tended to increase the proportion of LAD production by tillers at the expense of grain yield, which can be attributed to lower post‐anthesis precipitation. Oat types differed in main shoot and tiller LAD. Disadvantageous characteristics of naked oat, such as low single groat weight, were not associated with insufficient main shoot LAD. High tiller LAD in naked lines and the Minnesota‐adapted dwarf line that was not associated with high tiller grain yield in naked lines, in particular, indicates that tiller growth was enhanced at the expense of grain yield production. Application of N fertilizer at various rates did not have any effect on LAD.

Growth, development and yield of five sunflower hybrids

Studies were conducted to assess the physiological basis of variation in yield among five genotypes during the summer seasons of 1987 and 1989, using the techniques of growth and yield analysis. The sowing of second-crop sunflowers allowed maximum values of total dry matter to be reached that were quite similar for both years, between 581 and 821 g m −2. Total dry matter yields in 1987 were reached with lower maximum leaf area index (LAI) and lower total leaf area duration (LAD) than in 1989. In both years of testing, the hybrid SH-222, which has a somewhat longer cycle than the other hybrids, stood out not only for its maximum LAI, but also for its higher LAD after flowering, total LAD and maximum crop growth rate (CGR), and for maximum and final total dry matter. The high temperatures and low relative humidities during the two seasons affected pollination and formation of achenes, especially in 1987 and in the cultivars showing low autocompatibility (Arbung-133 and SH-31), which had the greatest dry weight per 1000 fertile achenes. There were positive significant correlations between maximum CGR, total LAD, number of fertile achenes per head and concentration of oil in the achenes, and yield of achenes. However, the correlation with the protein concentration in the achenes was negative. LAD after flowering, head fertility and maximum of total dry matter were also positively correlated with achene yield, but with significant statistics in only one of the two years studied. Their correlations were negative with the dry weight of 1000 fertile achenes.

Physiology of bunch groundnuts (Arachis hypogaeaL.)

SummaryTwenty-nine bunch groundnut genotypes were grown in theKharifseason 1980 and the summer season 1981 at Bangalore. Growth and yield analysis showed that the total dry-matter accumulation was low up to 30 days after sowing and increased linearly up to the 86th day in theKharifand up to harvest in the summer season. There were significant differences between genotypes in leaf area indices (LAI), the leaf area duration (LAD) and LAD between pod initiation and harvest (LADP) in both the seasons. The mean LAI of genotypes did not vary much between theKharifand the summer seasons up to the 66th day. However, during the later stages of growth the LAD was higher in the summer. The higher biological yield and productivity in the summer was attributed to the high LAD and LADP during the later stages of crop growth. LAD and total dry-matter accumulation at harvest were significantly correlated both in theKharif(r = 0–75) and the summer(r= 0–81). The mean total number of flowers over all 29 genotypes did not vary, but total number of pegs formed per plant differed significantly between genotypes in both theKharifand summer seasons. The percentage of flowers which produced pegs was 72–2 in summer as against 51–2 inKharif.The primary branches contributed 86'7 and 90–1%to the total number of pods per plant in theKharifand summer seasons respectively. The contribution of the first four nodes of primary branches was 85%in both seasons. The number of fruiting points (nodes having mature pods) per plant, found to be the most important yield-determining component, showed significant variation amongst the genotypes in both theKharifand summer seasons. In summer, length of mature-pod-bearing zone (MPBZ), number of nodes in MPBZ and number of kernels per plant were higher than in theKharifseason. It is suggested that selection and breeding should concentrate on improving LAD and LADP, total dry matter per plant, more primary branches per plant, more pods in the distal nodes of primary branches and more fruiting points (nodes in MPBZ) per plant.

Growth and Yield in Pure and Mixed Crops of Potato Cultivars

SUMMARYExperiments were made between 1977 and 1979 to investigate the possibility of raising potato yields by mixing together cultivars having different growth patterns. The experiments also included mixtures of unsprouted and sprouted seed of the same or different cultivars. In the first experiment (1977) Pentland Crown was mixed with Arran Pilot, Red Craig's Royal or Désirée and the binary mixtures (1:1) compared with the pure stands of each. Yield of tubers from the mixtures did not differ significantly from the mean of two components planted alone at wide or narrow spacing of the seed tubers. Two experiments with identical treatments (1978) included mixtures of Majestic and Désirée and of each cultivar with unsprouted and sprouted seed. Mixtures (1:1) yielded more tubers than the mean of the two components planted alone and at final harvest in one experiment unsprouted and sprouted Majesties gave 7·6 t/ha more than the mean of these and 6·9 t/ha more than the more productive culture (P < 0·05). Similar differences were obtained in the second experiment.In the final experiment (1979) the degree of sprout development at planting time was varied in the cultivar Majestic. Short or long sprouted seed was mixed with unsprouted seed and long sprouted Désirée was also mixed with unsprouted Majestic. Mixtures of the unsprouted cultivar with either long sprouted Majestic or Désiré exceeded, significantly, the mean yield of components planted alone by 4·1 and 5·8 t/ha, respectively, at a high level of fertilizer. As a mean of three experiments the mixture of sprouted and unsprouted Majesties yielded 6·26 t/ha more tubers than the mean of the components and 4·27 t/ha more than the higher yielding component in pure culture. Better light interception due to higher leaf area duration and a more persistent leaf canopy appeared to produce these effects.

III. Seed-yield relationships ofLupinus angustifoliuscv. ‘Unicrop’

Abstract In an August (1976) sowing of Unicrop (Lupinus angustifolius) at 7 plant densities (10–163 plants/m2) seed yield increased to a maximum of 575 g/m2 at 130 plants/m2. Irrigation during flowering and seed-filling reduced seed yield because of an unidentified root pathogen. A maximum leaf area index of 7 was reached 1 week after flowring, resulting in a high leaf area duration (LAD) during seed-filling. Mainstem and first-order pods per unit area accounted for most of the variation in seed yield (r = +0.84*** and +0.77*** respectively). Compensatory branching at lower plant densities did not occur. Irrigation reduced mainstem pod set on disease-free plants, but the yield loss was compensated for by increased production by branches. Increased vegetative growth of irrigated plants also lowered seed set on the mainstem but improved seed set in third- and fourth-order pods Seed number per pod and seed weight decreased at higher inflorescence orders. Seed number per pod was also reduced at high plant densities, but there was no response of seed weight to plant population. This lack of response may be related to high LAD at all densities.