Higher Net Assimilation Rate Research Articles

Fe toxicity tolerance is advantageous in rice growth recovery after Fe stress alleviation

AbstractBackgroundFe toxicity often inhibits rice growth on acid sulfate soils in tropical coastal lowlands. Previous studies in plant physiology and breeding have focused on high‐Fe stress, but not on growth recovery after stress alleviation.AimsThe objective of this study was to elucidate the morphophysiological characteristics in rice growth recovery from high‐Fe stress.MethodsWe evaluated the seedling growths of Taichung65 (T65) (Fe toxicity‐tolerant) and Ciherang (susceptible) in hydroponic culture, during the period of high‐Fe stress (250 mg Fe2+ L−1 for 12 or 18 days) and after stress alleviation.ResultsThe plant growth rate during recovery was negatively correlated with the leaf bronzing score (damage symptoms due to Fe toxicity) at the end of high‐Fe stress, which in turn was negatively correlated with the shoot Fe concentration. After 18‐day stress, T65 showed greater growth recovery than Ciherang, attributable to its higher net assimilation rate, higher transpiration rate (water uptake/green leaf area), and greater increase in total root length during recovery. In particular, T65 showed vigorous lateral root development in nodal roots that emerged during the stress period and vigorous growth of nodal roots that emerged during recovery.ConclusionsOur results suggest that tolerance to high‐Fe stress confers an advantage in growth recovery. It is likely that tolerance to Fe toxicity contributes not only to the maintenance of green leaf area at the end of stress but also to quick root growth recovery, leading to vigorous water uptake and high photoassimilation capacity after stress alleviation.

Effect of Irrigation Regimes and Applied Nitrogen Levels on Growth and Physiological Responses of Ryegrass

A field experiment was conducted at the Instructional-cum-Research (ICR) Farm, Assam Agricultural University, Jorhat. The experiment was laid out in split-plot design with three replications. The treatments consisted of five levels of irrigation in main plot viz., I0:Rainfed, I1: Irrigation at critical growth stages, I2: Irrigation at IW:CPE ratio of 1.0, I3: Irrigation at IW:CPE ratio of 1.2 and I4: Irrigation at IW:CPE ratio of 1.4 along with four levels of N- N0: 0 kg N/ha, N1: 30 kg N/ha, N2: 60 kg N/ha and N3: 90 kg N/ha in sub- plots. The soil of the experimental site was sandy loam in texture, medium in organic carbon, available N and available P2O5, acidic in reaction and low in available K2O. The result revealed that the highest leaf area index (LAI) recorded in irrigation at IW:CPE ratio of 1.4 at all the three cuts respectively during both the years. The crop growth rate (CGR), relative growth rate (RGR) and net assimilation rate (NAR) of ryegrass as influenced by different irrigation regimes were found to be non-significant at 30 DAS while at later growth stages i.e. 45 DAS, 60 DAS, 90 DAS and 120 DAS were significantly influenced during both the years. The application of irrigation at IW:CPE of 1.4 produced higher value of CGR, RGR but the highest NAR was recorded in rainfed treatment. The data on LAI as influenced by different N levels was found to be significant in all three cuts. Application of 90 kg N/ha recorded the highest LAI. The CGR, RGR and NAR as influenced by different N levels were found to non significant at 30 DAS but significantly influenced at later growth stage i.e. 45 DAS, 60 DAS, 90 DAS and 120 DAS during both the years. The highest data on CGR and RGR were recorded in 90 kg N/ha but the highest NAR was found in 0 kg N/ha.

Mesh Crop Cover Optimizes the Microenvironment in a Tropical Region and Modifies the Physiology and Metabolome in Tomato

In tropical regions, high light levels can lead to increased photooxidative damage in plants. Thus, reducing solar radiation could have a substantial impact on crop performance. This study aimed to evaluate the physiological responses and metabolic profile of two tomato varieties grown in microenvironments modified with cover meshes under a high light level and a warm climate. The experiment was achieved under high solar irradiance and an unfavorably high temperature. The varieties “Moneymaker” (MM) and “Campeche 40” (C40) were grown from 45 to 130 days after sowing at four solar irradiance levels: 100% (T1), 80% (T2), 75% (T3), and 50% (T4). In both varieties, the plants grown under the lowest irradiances (T3 and T4) were the tallest, with larger leaf areas, and accumulated more aerial and root biomass. Under moderate shading (T2), plants took better advantage of the light and had the highest photochemical quenching coefficient (qP) (C40 = 0.60 and MM = 0.48) and the highest electron transport rate (ETR). However, T3 and T4 plants had the highest net assimilation rate (23.6 and 23.9 µmol m−2 s−1 in C40, and 22.7 and 22.6 µmol m−2 s−1 in MM, respectively) and the highest A/Ci coefficients. Although both tomato varieties accumulate similar metabolites, MM leaves accumulate more glucose and C40 leaves accumulate more proline and valine. Furthermore, MM leaves accumulate more glycine and GABA under high radiation, and C40 leaves accumulate more proline and valine than leaves under 50% shade (T4). We conclude that using meshes in areas with high irradiance could be an alternative to reduce abiotic stress factors in plants.

Solar radiation utilization of five upland–paddy cropping systems in low-light regions promoted by diffuse radiation of paddy season

Solar radiation affects crop productivity in farmland ecosystems. Global dimming has resulted in decreased incident global radiation over recent decades, with a huge subsequent effect on food security. Attempting to increasing utilization of radiation and production to increase output, especially in multiple cropping systems, is a significant problem in low-light regions. Here, five upland–paddy cropping systems were evaluated in a low-light region during 2016–2017 and 2017–2018: Garlic–rice (GR), wheat–rice (WR), broad bean–rice (BR), rapeseed–rice (RR), and potato–rice (PR). Solar radiation and crop-related indicators were investigated to determine radiation utilization. The results showed that annual global radiation was 4056.97. MJ·m−2 and 3985.43 MJ·m−2 in 2016–2017 and 2017–2018, respectively, 13.69%–26.25% of which was wasted during the fallow season. Furthermore, the seasonal distribution of global radiation was differed to study years. The ratio_dif in paddy season was greater than 75%, whereas in upland season was less than 55%. Additionally, the annual radiation utilization efficiency (RUE) values of the crops investigated in this study were 0.53%–0.80% and RUE during upland season were 0.30%–0.95%, compared to 0.99%–1.35% during paddy season. The ratio_dif during paddy season had a greater contribution to RUE than that of the upland season, whilst the ratio_dif had a positive relationship with RUE. Therefore, in the low light region the high radiation utilization of upland-paddy systems could primarily be attributed to the efficient utilization of diffuse radiation by rice, which had a high radiation interception, net photosynthesis and net assimilation rate. This increase in diffuse radiation will further promote the efficient use of radiation in low-light regions. Furthermore, planting the upland crops with long growth period (garlic) and high planting intensity (wheat and rapeseed) could take advantage of limited global radiation in low-light regions. Our study clarifies RUE magnitude and its causes in upland–paddy cropping systems in low-light regions, while also providing a theoretical reference for grain production prediction and crop RUE improvement within the context of global dimming.

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.

The Accumulation of Biomass Pre- and Post-Silking Associated with Gains in Yield for Both Seasons under Maize–Rice Double Cropping System

Due to relatively low yield as well as low resources use efficiency with double rice (Oryza sativa L.) cropping systems (RR), exploring new cropping systems to increase yield and resources use efficiency simultaneously has become a large challenge of the middle reaches of the Yangtze River (MRYR). Our previous study demonstrated that the maize (Zea mays L.)–rice cropping system (MR) exhibited higher superiority of yield and resource use efficiency compared with the conventional double-rice cropping system. However, the reason for the yield increases in both maize and rice and the physiological processes involved in those two crops under MR are poorly understood. A 3-year field experiment was conducted at two sites (Wuxue and Jingmen) from 2016 to 2018 to examine the differences in dry matter (DM) accumulation, soil properties, and resources use efficiency between the MR and RR cropping systems. Compared with RR, the annual yield of MR was 18.2–26.3% and 15.4–31.5% higher across three years at Wuxue and Jingmen, respectively. The average yield of maize in MR was 36.5% and 21.9% higher than that of early rice in RR at Wuxue and Jingmen, respectively. The yield increase for maize was mainly attributed to the 29.7% (Wuxue) and 28.5% (Jingmen) increases in post-silking DM accumulation due to the higher plant growth rate promoted by the higher net assimilation rate and radiation use efficiency. For the late rice in MR, the average yield was 10.9% and 14.5% higher than that of late rice in RR at Wuxue and Jingmen, respectively, which was promoted by the 7.8–23.3% increase in pre-anthesis DM accumulation due to improved soil properties. Compared with RR, the MR cropping system exhibited increased soil pH, total organic carbon, and mineral nitrogen, and decreased the bulk density in the late rice season. As a result of greater yield in both seasons under MR, the annual accumulated temperature and radiation use efficiency, partial factor productivity from applied nitrogen, and water use efficiency of MR were 17.7–26.4%, 22.2–25.5%, 5.5–7.8%, and 33.6–48.7% higher than those of RR, respectively. We conclude that the higher yield in the MR than in the RR cropping system was mainly attributed to the accumulation of post-silking biomass due to maximized use of radiation in the maize season, and the accumulation of pre-anthesis biomass due to improved soil nutrients in the late rice season.

The potential of Central Java local black rice and red rice as drought tolerant cultivars

Black and red rice contain nutritional values not found in white rice. They contain anthocyanins which are beneficial to health. Drought stress can potentially reduce rice yield. So, it is necessary to develop local black and red rice into tolerant cultivars. This study used a completely randomized design (CRD) with cultivar factor (V) and drought stress level (K). Drought stress treatment was carried out when the plants were 35-95 DAP (days after planting) using the modified gravimetric method. Plant destruction was conducted at 7 and 21 DAT (days after treatment) to measure the growth analysis component. The observation of the growth analyses was plant dry weight, leaf area (LA), specific leaf area (SLA), relative growth rate (RGR), and net assimilation rate (NAR). Agronomic characters by observing shoot-root ratio and flowering age. The results showed drought stress decreased plant dry weight, leaf area, and relative growth rate on Sragen black rice. Jelitheng Karanganyar showed high RGR and NAR under drought stress and the fastest flowering age response. Wonogiri black rice gave the growth response by reducing specific leaf area. The highest shoot-root ratio was shown on Wonogiri black rice.

Preparing seedlings for dry spells: Drought acclimation in the seedlings of two tree species of a seasonal tropical dry forest

The effect of two drought acclimation treatments—high (HS) or moderated (MS) drought stress—on seedling growth was assessed in the two tree species Caesalpinia platyloba S.Watson (Fabaceae) and Ipomoea wolcottiana Rose (Convolvulaceae) in order to prepare them for dry spells. These species are mainly distributed in mature and disturbed sites, respectively, in a seasonal tropical dry forest in Jalisco, Mexico. Without acclimation, the seedlings of C. platyloba showed low values in both Specific Leaf Area (SLA) and Net Assimilation Rate (NAR), suggesting a conservative biomass allocation, while in I. wolcottiana, the high Relative Growth Rate (RGR), Root:Shoot ratio (R:S), and low SLA suggested seedling drought evasion. After the acclimation period, the seedlings of both species showed reduced biomass allocation to leaves, as indicated by the decrease in Leaf Mass Ratio (LMR). Additionally, increases in R:S suggested greater allocation to water capture during the short growth season. After the dry spell simulation, the control seedlings of C. platyloba showed negative NAR, but the relatively high NAR observed in the seedlings subjected to HS and MS suggested that these treatments were sufficient to endure drought stress. In I. wolcottiana, a sigmoid relationship described that seedlings’ RGR rapidly increased when NAR was raised. Contrastingly, in C. platyloba seedlings, the constant RGR increase related to the raise in NAR suggested a conservative use of water. In the I. wolcottiana seedlings, the HS treatment induced leaf abscission. Both species were plastic enough to acclimate to short periods of drought, but different levels of drought stress were necessary to acclimate the seedlings of each species. Suggested drought-acclimation treatments are to water the C. platyloba seedlings at 25% (HS) and I. wolcottiana seedlings at 50% (MS) of field capacity.

Transcriptional Changes in Pearl Millet Leaves under Heat Stress.

High-temperature stress negatively affects the growth and development of plants, and therefore threatens global agricultural safety. Cultivating stress-tolerant plants is the current objective of plant breeding programs. Pearl millet is a multi-purpose plant, commonly used as a forage but also an important food staple. This crop is very heat-resistant and has a higher net assimilation rate than corn under high-temperature stress. However, the response of heat resistant pearl millet has so far not been studied at the transcriptional level. In this study, transcriptome sequencing of pearl millet leaves exposed to different lengths of heat treatment (1 h, 48 h and 96 h) was conducted in order to investigate the molecular mechanisms of the heat stress response and to identify key genes related to heat stress. The results showed that the amount of heat stress-induced DEGs in leaves differs with the length of exposure to high temperatures. The highest value of DEGs (8286) was observed for the group exposed to heat stress for 96 h, while the other two treatments showed lower DEGs values of 4659 DEGs after 1 h exposure and 3981 DEGs after 48 h exposure to heat stress. The DEGs were mainly synthesized in protein folding pathways under high-temperature stress after 1 h exposure. Moreover, a large number of genes encoding ROS scavenging enzymes were activated under heat stress for 1 h and 48 h treatments. The flavonoid synthesis pathway of pearl millet was enriched after heat stress for 96 h. This study analyzed the transcription dynamics under short to long-term heat stress to provide a theoretical basis for the heat resistance response of pearl millet.

Effects of reduced nitrogen application rate on drip‐irrigated cotton dry matter accumulation and yield under different phosphorus and potassium managements

AbstractTo elucidate effects of reduced N application rate on dry matter accumulation and yield of drip‐irrigated cotton (Gossypium hirsutum L.) under different phosphorus and potassium managements (PK‐Ms), field studies with four reduced N application rates and four PK‐Ms were conducted in 2018 and 2019. Results show that after early peak boll‐forming (PB) stage, the leaf area (LA) in N3PK‐M3 was the highest among all treatments. The net assimilation rate (NAR), crop growth rate (CGR), boll dry weight (BDW), and boll growth rate (BGR) were highest in N2, followed by N3 with insignificant differences, and those parameters in PK‐M3 were the highest. The reproductive/vegetative biomass ratio (RVR) for N3PK‐M3 was the highest. The CGR, BDW, BGR, and NAR for N3PK‐M3 were insignificantly lower than those for N2PK‐M3, which increased yield in N2PK‐M3 and N3PK‐M3 treatments. Correlation analysis showed that BGR was positively related with CGR and NAR from peak flowering (PF) stage to boll opening (BO) stage, and CGR was significantly correlated with NAR and LA from PF to BO stage, and BO stage, respectively. Moreover, the yield was positively correlated with boll weight (BW) and boll number (BN), and BGR was significantly correlated with BN and BW from peak squaring stage to late PB stage. Therefore, high yield in N3PK‐M3 due to higher value in LA after boll‐forming stage, with higher NAR, CGR, RVR, and BGR, suggesting that early boll formation and successive partitioning of dry matter in boll growth were important factors for yield formation.

Plasticity of the Root System Architecture and Leaf Gas Exchange Parameters Are Important for Maintaining Bottle Gourd Responses under Water Deficit.

The evaluation of root system architecture (RSA) development and the physiological responses of crop plants grown under water-limited conditions are of great importance. The purpose of this study was to examine the short-term variation of the morphological and physiological plasticity of Lagenaria siceraria genotypes under water deficit, evaluating the changes in the relationship between the root system architecture and leaf physiological responses. Bottle gourd genotypes were grown in rhizoboxes under well-watered and water deficit conditions. Significant genotype-water regime interactions were observed for several RSA traits and physiological parameters. Biplot analyses confirmed that the drought-tolerant genotypes (BG-48 and GC) showed a high net CO2 assimilation rate, stomatal conductance, transpiration rates with a smaller length, and a reduced root length density of second-order lateral roots, whereas the genotypes BG-67 and Osorno were identified as drought-sensitive and showed greater values for average root length and the density of second-order lateral roots. Consequently, a reduced length and density of lateral roots in bottle gourd should constitute a response to water deficit. The root traits studied here can be used to evaluate bottle gourd performance under novel water management strategies and as criteria for breeding selection.

Functional growth analysis of diploid potato cultivars (Solanum phureja Juz. et Buk.)

Plant growth analysis has been widely used to study factors that influence plant growth. This analysis uses a set of quantitative methods that describe and analyze the growth of plants and their organs. It uses data from direct measurements (weight, area, volume) and quantifies and analyzes growth using indexes based on models defined by mathematical functions. This study conducted a functional growth analysis of diploid potato cultivars in Colombia. The functional growth analysis of diploid potato cultivars was carried out over three consecutive growing seasons in Medellín, Colombia. A randomized block design was used with two levels of fertilization and five repetitions. The first factor corresponded to the three potato cultivars, and the second factor was two fertilization levels: 260 and 778 kg of fertilizer per hectare. Samples were taken weekly, and each sample was an entire plant per experiment unit. The dry weight of each organ and the leaf area were measured. These measurements were used to calculate the relative growth rate, leaf area ratio, net assimilation rate, and specific leaf area. The development time was evaluated in accumulated degree-days with threshold temperatures of 2 and 29°C. The three cultivars recorded their highest net assimilation rate at 1,252 accumulated degree days (ADD), with values of 0.0002565, 0.0002021, and 0.0001778 g cm-2 ADD-1 in the ‘Latina’, ‘Guaneña’, and ‘Colombia’ cultivars, respectively. The Latina cultivar stood out in several physiological characteristics, including the fastest developing cultivar. ‘Latina’ also had the highest total dry mass accumulated in the cycle (271.05 g) and accumulated dry matter in tubers (237 g).

Phenotypic Plasticity, Biomass Allocation, and Biochemical Analysis of Cordyline Seedlings in Response to Oligo-Chitosan Foliar Spray

Cordyline is one of the most important indoor pot plants and has a high request in the global market. As a bio-stimulant, chitosan could be used to enhance the plant growth and productivity, despite the variation in growth analysis and phenotypic plasticity of several plant species in response to chitosan supplement. Cordyline seedlings were foliar sprayed with five concentrations of oligo-chitosan (0, 25, 50, 75, and 100 mg L−1) for 4 months. Oligo-chitosan induced rapid growth of cordyline seedlings, in terms of larger specific leaf weight (SLW) and higher relative growth rate (RGRA), as well as improving the efficiency of plant photosynthesis (high net assimilation rate (NAR) or low specific leaf area (SLA)). Root growth rate (RGRR) has also increased by 89.13% with the application of 50 mg L−1 oligo-chitosan, which reflected on higher plant biomass (BM) in comparison to the control. Consequently, root biomass (RM) showed the greatest plasticity index (PPI) that enhanced growth, productivity, and quality as well as the marketability of cordyline seedlings. Foliar spray of 50 mg L−1 oligo-chitosan improved plant growth, root development, and plasticity index, resulted in increased quality and marketability of cordyline seedlings.

Influence of Soil Amendment on the Relative Growth Rate and Net Assimilation Rate of Phaseolus vulgaris and Vigna aconitifolia

Background: Soil pH is one of the most important factors that contribute to crop growth and productivity. The present research was designed to assess the influence of soil amendment using organic manure and agricultural lime on the relative growth rate (RGR) and net assimilation rate (NAR) of Phaseolus vulgaris and Vigna aconitifolia grown on soils from different locations.
 Methodology: The three locations were: Akamkpa, Calabar Municipality and Odukpani. The pH for the three soil locations were 4.0, 7.0 and 9.0, respectively. The treatments were; control (0 g), OM1 (100 g organic manure), OM2 (200 g organic manure), AL1 (100 g agricultural lime), AL2 (200 g agricultural lime), OM1 + AL1 (50 g organic manure + 50 g agricultural lime) and OM2 +AL2 (100 g organic manure and 100 g agricultural lime).
 Results: Results obtained on the RGR of the leaf dry weight of P. vulgaris treated with OM2 was the highest (0.50 g/wk) followed by OM1 (0.41 g/wk). OM1 + AL1 had the highest RGR of the stem dry weight of P. vulgaris grown on soil from Calabar Municipality. In the RGR of the root dry weight, OM2 had the highest mean value in both plants grown on Akamkpa soil. Results obtained at 4 weeks after planting (WAP) revealed that there was significant (P<0.05) increase in NAR of plants grown on soil from Akamkpa. The highest NAR was obtained for V. aconitifolia treated with OM2 (0.0447 g/wk) followed by OM2 + AL2 (0.0057 g/wk) for both V. aconitifolia and P. vulgaris. P. vulgaris grown on Akamkpa and Odukpani soils treated with AL2 (0.0032 g/wk), OM1 + AL1 (0.0041 g/wk) and OM2+ AL2 (0.0062 g/wk) had the highest NAR at 8 WAP.
 Conclusion: The RGR and NAR of the two bean varieties were improved following treatments with organic manure and agricultural lime.

Open field experiment for the evaluation of Arundo donax ecotypes ecophysiology and yield as affected by soil water content

The high photosynthetic efficiency and the drought tolerance of Arundo donax L. contribute to its potential use as a suitable biomass crop for drought prone environments.A modelling approach to study net assimilation and stomatal conductance as influenced by available soil water content (ASWC) can be used to obtain threshold values to support the management of irrigation practice.Physiological model parameters, morphological (stem height and max diameter, number of leaves per stem), and productive traits (yield and biomass ash content), can support ecotypes selection activity, crucial for genetic improvement in a crop, such as A. donax, widely distributed in natural habitats, but characterized by no viable seeds.To this end, an open field experiment has been conducted comparing three A. donax L. clones collected from habitats representing a gradient of increasing temperature and declining water availability (Morocco; South Italy, and North Italy). Two irrigation treatments (rain-fed, and well-watered) and two different harvest dates (December and March) were also imposed as experimental factors.Physiological model involved light response curve approach measuring net assimilation and stomatal conductance under different light intensity and different actual ASWC. The obtained physiological curve parameters in relation to ASWC (maximum net assimilation - AN-sat, photosynthetic quantum efficiency - Qapp, and maximum stomatal conductance - Gs-sat) were well fitted by a two-segmented piecewise regressions. The segment breakpoints were computed at 43%, 39% and 65% of ASWC, for AN-sat, Qapp, and Gs-sat, respectively. This means that between 65% and 43% of ASWC, only stomatal conductance appeared to be influenced by the decrease of ASWC, reducing stomata opening, whereas the efficiency of net assimilation resulted unaffected by water depletion. The capacity to sustain high net assimilation rates untill low ASCW and the capacity to full recover net photosynthesis after a severe drought stress, emerged as crop traits contributing to explain the drought resistant aptitude of A. donax. No differences have been reported for any of the studied physiological parameters within ecotypes. On the contrary, the three clones exhibited differences in terms of biometric characters, biomass production and its ash content. The results of the study emphasize the multipurpose value of Moroccan ecotype reporting best performances in terms of both quantity and quality (highest biomass yield - 26.4 t ha−1 - lowest ash content 4.8%).

Study of some physiological and yield traits of two ginger (<i>Zingiber officinale Rosc.</i>) cultivars

A comparative study on some physiological and yield traits of ginger was undertaken using two distinct ginger varieties, The experiments was laid out on flats in a randomized complete block design replicated five times and analysed as a split-plot experiment. The main-plot treatments were the two varieties and the sub-plot treatments were three sett sizes of the two varieties (10g, 20g and 30g). Each sub-plot was a 2.4m x 0.5m flat bed, each bed containing 20 setts planted at 20cm x 20cm spacing. UG 1 and UG 2 . The effects of sett sizes (10, 20 and 30g) on these traits were examined. The number of shoots and leaf area per stand, plant height, rhizome yield and the number of rhizome fingers increased with sett size. UG 1 produced significantly more shoots and rhizome fingers per stand and was also higher yielding than UG 2 which produced significantly taller plants, all at 0.05 probability level. There was no significant difference between the cultivars for leaf production. The physiological attributes for high yield in the ginger varieties included early foliage development and high yield capacity to channel dry matter into the rhizomes. High net assimilation rate (NAR) and relative growth rate (RGR) values did not ensure high yields. Keywords: Ginger, Zingiber officinale , growth parameters, RGR, NAR, LAR, yield

Contrasting acclimation abilities of two dominant boreal conifers to elevated CO2 and temperature.

High latitude forests will experience large changes in temperature and CO2 concentrations this century. We evaluated the effects of future climate conditions on 2 dominant boreal tree species, Pinus sylvestris L. and Picea abies (L.) H. Karst, exposing seedlings to 3 seasons of ambient (430ppm) or elevated CO2 (750ppm) and ambient temperatures, a+4°C warming or a+8°C warming. Pinus sylvestris responded positively to warming: seedlings developed a larger canopy, maintained high net CO2 assimilation rates (Anet ), and acclimated dark respiration (Rdark ). In contrast, carbon fluxes in Picea abies were negatively impacted by warming: maximum rates of Anet decreased, electron transport was redirected to alternative electron acceptors, and thermal acclimation of Rdark was weak. Elevated CO2 tended to exacerbate these effects in warm-grown Picea abies, and by the end of the experiment Picea abies from the +8°C, high CO2 treatment produced fewer buds than they had 3years earlier. Treatments had little effect on leaf and wood anatomy. Our results highlight that species within the same plant functional type may show opposite responses to warming and imply that Picea abies may be particularly vulnerable to warming due to low plasticity in photosynthetic and respiratory metabolism.

The invasive duckweed Lemna minuta Kunth displays a different light utilisation strategy than native Lemna minor Linnaeus

Lemna minuta Kunth is an invasive, alien duckweed that is present throughout much of Europe, where it competes with native congeneric Lemna minor Linnaeus. Previously, L. minuta was found to grow faster than L. minor. The aim of this study was to determine whether the rapid growth of invasive L. minuta is based on differential light utilisation. For this purpose, the growth performance of L. minuta was compared with that of L. minor under a range of different light intensities. Both physiological and morphological parameters were determined. L. minuta showed a higher Relative Growth Rate (RGR) than L. minor when grown under medium and high intensities. Further analysis showed that, at high light intensities, L. minuta has a higher Net Assimilation Rate (NAR), and displays more photochemical quenching (qP) and a higher quantum yield (Y(II)) than L. minor. In contrast under low light intensities L. minor displayed a marginally higher RGR, due to a greater Leaf Area Ratio (LAR), and higher chlorophyll content than L. minuta. The results indicate two distinct light utilisation strategies, and reveal that the invasive species L. minuta takes more advantage from high intensity light conditions. In turn, this may influence plant distribution and, consequently, ecosystem management by relevant authorities.

OVERCOMING ABIOTIC SHADES FOR SWEETPOTATO (IPOMOEA BATATAS L.) IN THE HIGHLAND OF PAPUA, INDONESIA: THE ADAPTATION OF VARIETIES AND STICKS INCLINATION ANGLES

Abiotic shades due to the high level of cloud are the major problem causing a low level of sweetpotato (Ipomoea batatas L.) photosynthesis in the higland of Papua, Indonesia. In order to optimize the growth and production of sweetpotato, it needs to engineer the growing environment for the crop. This study aims to learn the growth, production and photosynthesis efficiency (Eµ) by combining varieties and sticks inclination angles on (1.560 m asl) from April to September 2016. It was conducted using a Split-Plot Design with three replications. The main plot was three sweet potato varietes: Siate, Papua Salosa and Cangkuang, while the subplot was the inclination of sticks with three angles: 90º, 60º, 45º and without using sticks. The result shows that a combination of Cangkuang and 90º stick inclination produces the highest total dry matter and tubers (326.9 g/plant and 248.7 g/plant respectively). The highest net assimilation rate was obtained in combination of Cangkuang with stick inclination angles treatments 90º and 60º for 125.2 mg.cm2.day-1 and 105.3 mg.cm2.day-1, the leaf area index ranged from 0.9-5.5. The highest tubers yield was achieved by the Cangkuang with 90º and 60º sticks inclination angles treatments, which are 31.53 t.ha-1 and 28.86 t.ha-1 respectively, with the harvest indexes around 36-62 %, in which the tubers yield and the harvest indexes have significant correlations.The highest photosynthesis efficiency was achieved by the Cangkuang with 90º (3.83 %) and 600 (3.34 %) sticks inclination angles treatments, while the lowest one was done by the Siate and without sticks (0.92 %) treatment. As a conclusion, the higher sticks inclination angles applied on the sweetpotato varieties, particularly whose wider leafs, under abiotic shade conditions may increase crop growth rates, total and tuber dry matters, tubers yield, harvest indexes, and photosynthesis efficiency rates.

Effect of Plant Density on Sweet and Biomass Sorghum Production on Semiarid Marginal Land

Plant density substantially affects sorghum (Sorghum bicolor (L.) Moench) productivity. Therefore, density optimisation plays a pivotal role in crop management practices. A 2-year field experiment was conducted on sandy loam marginal land in Ordos, Inner Mongolia, China, to (1) determine the mechanism underlying the impact of plant density (i.e. 6.0, 7.5, 9.0, 10.5 and 12.0 plant m−2) on biomass yield, quality and photosynthetic efficiency and (2) determine the optimum plant density for sweet sorghum variety GT-3 and biomass sorghum variety GN-4. Results indicate that plant height, leaf area index (LAI), leaf area duration (LAD) and biomass yield increased as plant density increased, but tiller number, stem diameter and net assimilation rate (NAR) decreased. The growth period between elongation and anthesis dates was crucial to sorghum productivity; during this period, LAD was the determining factor for biomass yield. Increase in plant density up to 10.5 plant m−2 led to a high LAI level, an extended LAD, a high and stable NAR and a positive balance between photosynthesis and respiration processes, all of which contributed to highest biomass yield (13.2 t ha−1). Ultimately, sweet-type variety GT-3 demonstrated the highest theoretical ethanol yield (4147 L ha−1) and relative feed value (112.3%) compared with biomass-type variety GN-4.