D After Sowing Research Articles

Yield enhancement and grain vis-à-vis malt quality of barley (Hordeum vulgare L.) genotypes as influenced by clipping and foliar application of zinc

Barley is mostly grown under rainfed condition on poor to marginal soils having deficit soil moisture and zinc (Zn) deficiency, which limits the barley productivity and grain quality. Zn spray could improve the productivity and grain quality in these soils. Therefore, this two-year field study was conducted to assess the influence of barley genotypes and clipping stages vis-à-vis Zn foliar application in barley productivity and grain quality. The experiment consisted of three barley genotypes; DWRUB 52, PL 807, and PL 426 and five clipping management; control, clipping at 50 d after sowing (DAS), clipping at 60 DAS, clipping at 50 DAS and ZnSO4 foliar spray @ 0.5% at anthesis + early milk stages and clipping at 60 DAS and ZnSO4 foliar spray @ 0.5% at anthesis + early milk stages. Barley genotype PL 426 showed in maximum lodging, protein content and yield, grain hardness, and husk content, while, DWRUB 52 gave the highest grain yield, Zn content, starch content, hectoliter weight, and bold grain proportions. Foliar spray of ZnSO4 @ 0.5% at anthesis + early milk stages significantly enhanced the grain yield of 12.5 and 12.7% with clipping at 50 DAS and 9.0 and 8.8% with clipping to 60 DAS than control crop during the first and second year, respectively. Zn content, protein content and yield, bold grains, and diastatic power were significantly improved over control with these treatments. Zn foliar application in combination with clipping may be opted to maximize the barley productivity, Zn concentration, and grains quality.

Silicon and growth regulator induced defence against maize fall armyworm, Spodoptera frugiperda (J.E. Smith)

A microplot field experiment was conducted to study the effect of silicon sources and growth regulator against maize fall armyworm, Spodoptera frugiperda at Thoppur village of Virudhunagar district during Rabi, 2021-22. Basal application of different doses of calcium silicate and foliar application of silicic acid and potassium silicate were carried out. The results revealed that 150 kg of calcium silicate/ha + 0.2% silicic acid at 15 d after sowing (DAS) + 50 ppm GA at 30 DAS was found to be effective in reducing fall armyworm (FAW) population (1.23 larvae/plant) followed by treatment with 75 kg of calcium silicate/ha + 0.2% silicic acid at 15 DAS + 50 ppm GA at 30 DAS (1.27 larvae/plant). Regarding leaf and cob damage, the treatment with 150 kg of calcium silicate/ha + 0.2% silicic acid at 15 DAS + 50 ppm GA at 30 DAS was found to be most effective and significantly superior over all other treatments by recording lowest mean leaf damage score of 1.63/plant and mean cob damage score of 1.13/plant followed by the treatment with 75 kg of calcium silicate/ha + 0.2% silicic acid at 15 DAS + 50 ppm GA at 30 DAS with 1.66 leaf score/plant and 1.35 cob score/plant.

High-throughput calculation of organ-scale traits with reconstructed accurate 3D canopy structures using a UAV RGB camera with an advanced cross-circling oblique route

The measurement of organ-scale traits in large-scale fields remains a bottleneck in genotype-phenotype association studies for crop improvement. To address this issue, an advanced cross-circling oblique (CCO) route was proposed, consisting of multiple single-circle routes. Using multi-view images from lightweight UAVs with the CCO route, 3D crop canopies were reconstructed for maize, cotton, and sugar beet. Organ-scale traits were estimated from the CCO-derived and traditional five-directional oblique (FDO)-derived 3D canopy models and were compared to manual measurements. An algorithm was further proposed to compare the image utilisation efficiency between the CCO route and FDO route with three indicators, including the total utilisation (TU), effective utilisation (EU), and occlusion rate (OR). The results showed that the proposed CCO route can obtain complete canopy structures throughout the growth stages for crops with relatively wide-row planting, such as maize. For densely planted crops like cotton, the full canopy structure at early growth stages (47 d after sowing (DAS)) and the upper parts of the canopy architecture at later growth stages (71 and 90 DAS) could be obtained. The leaf length and width from different layers estimated from CCO-derived models were in good agreement with manual measurements for maize (R2 = 0.93, RMSE = 3.05 cm, nRMSE = 4.7% and R2 = 0.88, RMSE = 0.49 cm, nRMSE = 5.5% for leaf length and leaf width, respectively) and cotton (R2 = 0.81, RMSE = 1.16 cm, nRMSE = 8.6% and R2 = 0.93, RMSE = 0.99 cm, nRMSE = 7.2% for leaf length and leaf width, respectively). CCO-derived 3D canopy models also provided higher accuracy for organ-scale trait estimation than FDO-derived 3D canopy models (R2 of 0.80 versus 0.76 for both leaf length and width estimation, respectively). Regarding image utilisation, the CCO route outperformed the FDO route, with an average value of 124% higher in EU and 11.7% lower in OR, tested on sugar beet varieties with different canopy structures. The proposed CCO route adopts a non-linear mobile route to obtain canopy images from more perspectives, taking into account both the model accuracy and efficiency. Although the flight altitude of the CCO in this study was relatively low (4 m above the canopy), the same model accuracy can be achieved at higher flight altitudes using a higher-quality camera, thus significantly reducing image acquisition time. This study represents the first time that accurate crop structures in large-scale fields were characterised using a method featuring mobility, affordability, throughput, accuracy, and efficiency. The proposed method could provide novel opportunities for accelerating plant breeding and precision agriculture.

Complementary effect of zoo compost with mineral nitrogen fertilisation increases wheat yield and nutrition in a low-nutrient soil

Excess nitrogen (N) fertiliser use in agriculture is associated with water pollution and greenhouse gas emissions. While practices and programs to reduce N fertiliser application continue to be developed, inefficient fertiliser use persists. Practices that reduce mineral N fertiliser application are needed in a sustainable agricultural ecosystem to control leaching and gaseous losses for environmental management. This study evaluated whether fully or partially replacing mineral N fertiliser with zoo compost (Perth Zoo) could be a good mitigation strategy to reduce mineral N fertiliser application without affecting wheat yield and nutrition. To achieve this, a glasshouse experiment was conducted to assess the complementary effect of zoo compost and mineral N fertiliser on wheat yield and nutrition in a sandy soil of southwestern Australia. Additionally, a chlorophyll meter was used to determine whether there was a correlation between chlorophyll content and soil mineral N content, grain N uptake, and grain protein content at the tillering (42 d after sowing (DAS)) and heading (63 DAS) growth stages. The standard practice for N application for this soil type in this area, 100 kg ha -1 , was used with a soil bulk density of 1.3 g cm -3 to calculate the amount of mineral N (urea, 46% N) and Perth Zoo compost (ZC) (0.69% N) for each treatment. Treatments comprised a control (no nutrients added, T1), mineral N only (100 kg N ha -1 , T2), ZC only (100 kg N ha -1 , T7), and combinations of mineral N and ZC at different rates (mineral N at 100 kg N ha -1 + ZC at 25 kg N ha -1 (T3), mineral N at 75 kg N ha -1 + ZC at 25 kg N ha -1 (T4), mineral N at 75 kg N ha -1 + ZC at 50 kg N ha -1 (T5), and mineral N at 50 kg N ha -1 + ZC at 50 kg N ha -1 (T6)). The T6 treatment significantly increased grain yield (by 26%) relative to the T2 treatment. However, the T7 treatment did not affect grain yield when compared to the T2 treatment. All treatments with mineral N and ZC in combination significantly improved the 1 000-grain weight compared to the T2 treatment. Chlorophyll content was better correlated with soil mineral N content ( r = 0.61), grain N uptake ( r = 0.62), and grain protein content ( r = 0.80) at heading (63 DAS) than at tillering (42 DAS). While ZC alone could not serve as an alternative to mineral N fertiliser, its complementary use could reduce the mineral N fertiliser requirement by up to 50% for wheat without compromising grain yield, which needs to be verified in the field. Chlorophyll content could be used to predict soil mineral N at the heading stage, and further studies are warranted to verify its accuracy in the field. Overall, the application of ZC as part of integrated nutrient management improved crop yield with reduced N fertiliser application.

Developing functional relationships between sesame growth, development, and nitrogen nutrition during early season

AbstractPlants, being sessile, are subjected to multiple environmental stresses of varying intensity throughout their life cycle. Among the stresses, low fertility, drought, salinity, and nonoptimal temperatures limit crop productivity worldwide. Functional relationships between leaf N and crop growth are prerequisites to developing management tools that optimize productivity in the field. An outdoor pot‐culture experiment was conducted to determine the relationship between leaf N and sesame (Sesamum indicum L.) growth and development. Plants were grown in pots filled with fine sand and irrigated with full‐strength Hoagland's nutrient solution until 10 d after sowing (DAS). Five N treatments were then imposed: one treatment of full‐strength Hoagland's nutrient solution (control, 100% N), and four reformulations of Hoagland's nutrient solution containing reduced N at 60, 20, 10, and 0% of the control. Treatments were maintained until plants were harvested at 31 DAS. Growth, including several root traits, photosynthesis, and leaf N were measured at the end of the experiment. Maximum values were achieved at 5.3% leaf N in the leaves except for transpiration rate, stomatal conductance, and root/shoot ratio. Even though all growth rates declined with lower leaf N, the leaf area expansion among shoot and root volume among the root growth traits were most sensitive to leaf N. Among the root developmental traits, number of root tips was more sensitive to leaf N than other parameters. Among the plant dry components, leaf dry weight had the most considerable decrease. The root/shoot ratio increased under N deficiency. These N stress response indices and critical leaf N levels for various growth processes will help model and manage sesame crops in the field.

Fenpyrazone effects on succeeding crops in annual double-cropping areas on the North China Plain

Fenpyrazone is a novel 4-hydroxyphenylpyruvate dioxygenase (HPPD)-inhibiting herbicide used for postemergence (POST) application to control annual monocotyledon and dicotyledon weeds in summer maize (Zea mays L.). Annual double-cropping systems are popular on the North China Plain, especially summer maize in rotation with winter wheat (Triticum aestivum L.) or garlic (Allium sativum L.). In addition, vegetable crops have shown different levels of sensitivity to HPPD-inhibiting herbicides that were applied to preceding maize fields. However, there is no information about the effects of fenpyrazone on the succeeding crops. Here, field experiments were conducted twice at Dawenkou and Mazhuang to evaluate the response of successive rotation crops such as winter wheat, garlic and spinach (Spinacia oleracea L.) to fenpyrazone that was applied to preceding summer maize fields. Compared with the untreated weed-free control, none of the fenpyrazone treatments resulted in significant differences in the emergence of wheat, garlic and spinach at either location. When fenpyrazone was applied at 3 times the recommended rate to the preceding maize fields, there was no significant reduction in the wheat and garlic biomass despite the height of the garlic plants being reduced by 4.1% at 20 d after sowing (DAS) compared to that of the untreated weed-free control. Compared with wheat and garlic, spinach was more sensitive to fenpyrazone applications to preceding summer maize fields, and it reduced the plant heights by 2.6–17.1% at 20 DAS compared to those in the untreated weed-free control, with the loam soil in Mazhuang causing a higher biomass reduction than the sandy loam soil in Dawenkou. However, the biomass reduction stopped at 40 DAS, and no yield reduction was observed at harvest for all the fenpyrazone treatments at both locations. Based on this study, farmers on the North China Plain can safely grow winter wheat, garlic and spinach following fenpyrazone POST application at the recommended rate to preceding summer maize.

An alternative to polyethylene film mulch: Field evaluation of biodegradable film mulch on winter potato in the south of China

AbstractPolyethylene (PE) film mulching (PM) contributes to the increase of crop yields and farmer incomes at the expense of environment. We performed a 2‐yr field experiment to evaluate the possibility of replacement of PM with poly(butylene‐adipate‐co‐terephthalate)‐based biodegradable film mulching (BM) for winter potato (Solanum tuberosum L.) in the south of China. Both PM and BM treatments showed higher soil temperature and water content than no mulching (NM), and there was no significant difference between PM and BM before 60 d after sowing (DAS). Because of the breakdown of biodegradable film, reduced soil temperature and water content were observed in the BM treatment when compared to PM after 60 DAS, whereas no significant difference was observed in potato yield as well as marketable yield between PM and BM treatments, leading to higher water use efficiency in PM than BM. The net revenues of treatments BM and PM were increased by $1,015 and $1,720 ha−1 in growing season 2015–2016, and $967 and $1,295 ha−1 in 2016–2017, respectively, compared to NM. The PE film was barely degraded, whereas biodegradable film residue was reduced to an extremely low level with less than 5 kg ha−1 on field at 330 DAS. Therefore, BM is a viable and eco‐friendly alternative to PM for increasing yield of winter potato in the south of China.

Critical Period for Palmer Amaranth (Amaranthus palmeri) Control in Pickling Cucumber

AbstractField studies were conducted in North Carolina to determine the critical period for Palmer amaranth control (CPPAC) in pickling cucumber. In removal treatments (REM), emerged Palmer amaranth were allowed to compete with cucumber for 14, 21, 28, or 35 d after sowing (DAS) in 2014 and 14, 21, 35, or 42 DAS in 2015, and cucumber was kept weed-free for the remainder of the season. In the establishment treatments (EST), cucumber was maintained free of Palmer amaranth by hand removal until 14, 21, 28, or 35 DAS in 2014 and until 14, 21, 35, or 42 DAS in 2015; after this, Palmer amaranth was allowed to establish and compete with the cucumber for the remainder of the season. The beginning and end of the CPPAC, based on 5% loss of marketable yield, was determined by fitting log-logistic and Gompertz equations to the relative yield data representing REM and EST, respectively. Season-long competition by Palmer amaranth reduced pickling cucumber yield by 45% to 98% and 88% to 98% during 2014 and 2015, respectively. When cucumber was planted on April 25, 2015, the CPPAC ranged from 570 to 1,002 heat units (HU), which corresponded to 32 to 49 DAS. However, when cucumber planting was delayed 2 to 4 wk (May 7 and May 21, 2014 and May 4, 2015), the CPPAC lasted from 100 to 918 HU (7 to 44 DAS). This research suggested that planting pickling cucumber as early as possible during the season may help to reduce competition by Palmer amaranth and delay the beginning of the CPPAC.

Effect of Propaquizafop and Imazethapyr Mixture on Weed Dynamics, Growth, Yield and Economics of Soybean [Glycine max (L.) Merill

The results of field experiments conducted during Kharif seasons of 2013 and 2014 to adjudge the efficacy of propaquizafop and imazethapyr mixture (tank mixed) to combat weeds and impact the growth and yield of soybean are reported. The treatments consisted of four doses of propaquizafop + imazethapyr mixture (47 + 70, 50 + 75, 53 + 80 and 56 + 85g ha−1), sole application of propaquizafop (75 g ha−1) and imazethapyr (100 g ha−1) as early post-emergence and pendimethalin (1000 g ha−1) as pre-emergence, hand weeding(HW) twice at 20 and 40 d after sowing(DAS)and weedy check. The dry matter accumulation for all the recorded weed flora was found the lowest in combined application of herbicides rather than their sole application, being higher under propaquizafop + imazethapyr mixture applied at 53 + 80 g ha−1 or higher rate (56 + 85 g ha−1). Higher values of growth parameters (plant height, branches plant−1, nodules plant−1), yield attributes (pods plant−1, seeds pod−1, seed index), yield and B: C ratio were recorded under propaquizafop + imazethapyr mixture applied at 56 + 85 g ha−1 followed by 53 + 80 g ha−1 which were comparable to hand weeding twice at 20 and 40 DAS.

Weed control in conventional soybean with pendimethalin followed by imazethapyr plus imazamox/quizalofop

The objectives of this study were to evaluate the efficacy of pendimethalin applied pre-emergence (PRE) followed by post-emergence (POST) application of imazethapyr + imazamox/quizalofop-p-ethyl for weed control and their effect on conventional soybean injury, yield attributes, and yield. Field experiments were conducted in 2013 and 2014 in conventional soybean. Herbicide treatments provided ≥90%, 70%, and 85% control of crowfoot grass, large crabgrass, and goosegrass, respectively, and ≤80% control of false amaranth and horse purslane at 30 d after sowing (DAS). At 60 DAS, pendimethalin applied alone or followed by hand-hoeing/quizalofop-p-ethyl/imazethapyr + imazamox provided 100% control of goosegrass and 65%–100% control of crowfoot grass/large crabgrass. Pendimethalin followed by imazethapyr + imazamox/quizalofop-p-ethyl as well as quizalofop-p-ethyl applied alone resulted in complete control of crowfoot grass, large crabgrass, and goosegrass, but control of broadleaf weeds was variable. Pendimethalin followed by imazethapyr + imazamox at 70 g ha−1 at 28 DAS, imazethapyr + imazamox at 60 or 70 g ha−1 at 21 DAS followed by quizalofop-p-ethyl at 37.5 g ha−1 at 42 DAS resulted in soybean branch numbers per plant, number of pods per plant, and soybean seed yield comparable to weed-free control. Control of Benghal dayflower and purple nutsedge was not acceptable.

Short Response of Spring Wheat to Tillage, Residue Management and Split Nitrogen Application in a Rice-Wheat System

A field experiment was conducted to study the impact of tillage, crop residue management and nitrogen (N) splitting on spring wheat (Triticum aestivum L.) yield over 2 yr (2010-2012) in a rice (Oryza sativa L.)-wheat system in northwestern Pakistan. The experiment was conducted as split plot arranged in randomized complete blocks design with three replications. Treatments comprised six tillage and residue managements: zero tillage straw retained (ZTsr), zero tillage straw burnt (ZTsb), reduced tillage straw incorporated (RTsi), reduced tillage straw burnt (RTsb), conventional tillage straw incorporated (CTsi), and conventional tillage straw burnt (CTsb) as main plots and N (200 kg ha−1) was applied as split form viz., control (no nitrogen & no splitting, N0S0); 2 splits of total N, half at sowing and half at the 1st irrigation (i.e., 20 d after sowing (DAS)) (NS1); 3 splits of total N, 1/3 at sowing, 1/3 at the 1st irrigation, and 1/3 at the 2nd irrigation (NS2); 4 splits of total N, 1/4 at sowing, 1/4 at the 1st irrigation, 1/4 at the 2nd irrigation (45 DAS), and 1/4 at the 3rd irrigation (70 DAS) (NS3); and 4 splits of total N, 1/4 at the 1st irrigation, 1/4 at the 2nd irrigation, 1/4 at the 3rd irrigation, and 1/4 at the 4th irrigation (95DAS) (NS4) as sub plots. The results showed that the most pikes m−2, grains/spike, 1000-grain weight, grain yield, and N use efficiency (NUE) were obtained at zero tillage, straw retained and 4 splits application of total N (i.e., at sowing 20, 45 and 70 d after sowing). The results indicated that ZTsr with application of 200 kg N ha−1 in 4 equal splits viz. at sowing 20, 45 and 70 d after sowing is an appropriate strategy that enhanced wheat yield (7436-7634 kg ha−1) and N efficiency (28.6-29.5 kg kg−1) in rice-wheat system.

Uptake of 14C-atropine and/or its transformation products from soil by wheat (Triticum aestivum var Kronjet) and their translocation to shoots

Plant uptake of toxins and their translocation to edible plant parts are important processes in the transfer of contaminants into the food chain. Atropine, a highly toxic muscarine receptor antagonist produced by Solanacea species, is found in all plant tissues and can enter the soil and hence be available for uptake by crops. The absorption of atropine and/or its transformation products from soil by wheat (Triticum aestivum var Kronjet) and its distribution to shoots was investigated by growing wheat in soil spiked with unlabeled or 14C-labeled atropine. Radioactivity attributable to 14C-atropine and its transformation products was measurable in plants sampled at 15 d after sowing (DAS) and thereafter until the end of experiment. The highest accumulation of 14C-atropine and/or its transformation products by plants was detected in leaves (between 73 and 90% of the total accumulated) with lower amounts in stems, roots, and seeds (approximately 14%, 9%, and 3%, respectively). 14C-Atropine and/or its transformation products were detected in soil leachate at 30, 60, and 90 DAS and were strongly adsorbed to soil, with 60% of the applied dose adsorbed at 30 DAS, plateauing at 70% from 60 DAS. Unlabeled atropine was detected in shoots 30 DAS at a concentration of 3.9 ± 0.1 μg kg−1 (mean ± SD). The observed bioconcentration factor was 2.3 ± 0.04. The results suggest a potential risk of atropine toxicity to consumers.

Protection of growth in response to 28-homobrassinolide under the stress of cadmium and salinity in wheat

This study examines the impact of 28-homobrassinolide (HBL) in alleviating the effects of cadmium (Cd) and salinity (NaCl) on wheat plants solely and against the synergy. The surface sterilized seeds of Triticum aestivum cv. PBW-373 were sown in the soil amended either with salinity or cadmium or both. The foliage in was sprayed at 20d after sowing (DAS) both in stressed and non-stressed plants. The spray of HBL at 20 DAS increased almost all the parameters while decreased the H2O2 content and lipid peroxidation in the leaves. The presence of cadmium and/or salinity decreased the values for all the growth and photosynthetic parameters but improved the activity of antioxidant enzymes and proline content in 30d old plants. However, the ill effects observed under NaCl and/or Cd treatment were completely overcomed by the spray of HBL to the plants at 20d stage. The spray of HBL to stressed plants further increased the antioxidant enzyme activities and proline content thereby giving tolerance to the plants against the stress.

Relationships among soil respiration, soil temperature and dry matter accumulation for wheat-maize intercropping in an arid environment

Liu, S. B., Chai, Q. and Huang, G. B. 2013. Relationships among soil respiration, soil temperature and dry matter accumulation for wheat-maize intercropping in an arid environment. Can. J. Plant Sci. 93: 715–724. Spring wheat (Triticum aestivum L.) intercropped with maize (Zea mays L.) offers an opportunity to boost grain production in short-season areas, but little is known about the sustainability of the intercropping system. This study, conducted at an arid irrigation site in 2009 and 2010, determined water consumption and soil respiration (Rs) characteristics and their relationships to soil temperature (Ts) and above-ground dry matter (DM) accumulation for wheat/maize (W/M) intercropping compared with sole wheat and sole maize. The W/M intercropping had a co-growth period of 70-80 d, allowing the two intercropped species to complete their life cycles. Maximum DM rate for the wheat in the W/M system was significantly greater than that for sole wheat (57 vs. 51 g d−1), which occurred at around 72 to 77 d after sowing (DAS), whereas the maximum DM rate for the maize in the W/M system was between 31.6 and 44.9 g m−2 d−1, or 30 to 43% lower than that of sole maize. The ercroppedhe umulation of a thetime to reach maximum DM was 96 DAS in 2009 and 80 DAS in 2010 for sole maize, and the corresponding time for the intercropped maize was delayed by 6 to 10 d. Soil respiration and DM was a curvilinear relationship; with the increase in DM accumulation, Rs increased, reached a peak at the early flowering stage for wheat and at the silking stage for maize, and then declined. Soil respiration increased linearly with increases in soil temperature during the growth period for both sole and intercropping, suggesting that farming practices aimed at reducing soil temperature will be effective in reducing carbon emissions. Evapotranspiration during the co-growth period averaged 44.1 mm for sole wheat and 48.5 mm for the intercropped wheat and 57.0 mm for sole maize and 48.0 mm for the intercropped maize, but soil water status had little or no effect on Rs. Wheat/maize intercropping had greater grain yield with lower soil respiration over the corresponding sole plantings, and it can serve as a sustainable cropping system for arid irrigation areas.

Interactive Effect of GA3, N and P Ameliorate Growth, Seed and Fibre Yield by Enhancing Photosynthetic Capacity and Carbonic Anhydrase Activity of Linseed: A Dual Purpose Crop

Linseed (Linum usitatissimum L.) is an important dual-purpose, industrial crop. Its seeds are used for the extraction of oil and stem for fibres. However, the production of linseed is not going parallel with the increasing demand of its products. The present work was carried out with an aim to find out whether exogenous application of gibberellic acid (GA3) with or without graded levels of nitrogen (N) and phosphorus (P) could improve the performance of three linseed genotypes Parvati, Shekhar and Shubhra together with minimizing the costly fertilizer input and losses. Four combinations of N and P, viz., 0 mg N+0 mg P kg−1 soil (N0P0), N13.4P4.46, N26.8P8.94 and N40.2P13.4 were constituted. Half dose of each combination was applied basally at the time of sowing and remaining half dose was given at 40 d after sowing (DAS) as foliar spray along with 10−6 mol L−1 GA3. Prior to sowing, the seeds of each linseed genotype were grouped in to two, one group of seeds was soaked in 0 mol L−1 GA3 (control) and the other group was soaked in 10−6 M GA3 solution, each for 8 hours. Treatments were comprised of (i) 0 mol L−1 GA3+N0P0 (T0, control), (ii) 10−6 mol L−1 GA3 + N134P446 (T1), (iii) 10−6 mol L−1 GA3+N26.8P8.94 (T2) and (iv) 10−6 mol L−1 GA3+N40.2P13.4 (T3). The crop performance was assessed in terms of growth, physiological and biochemical parameters at 60 and 75 DAS and yield attributes at harvest (175 DAS). The results showed a parallel increase in most of the parameters with increasing levels of N and P. However, application of 10−6 mol L−1 GA3 in association with N26.8P8.94 proved best, it enhanced seed yield, oil yield and fibre yield by 83.3, 97.3 and 78.7%, respectively accompanied with increase in net photosynthetic rate, carbonic anhydrase activity and dry matter accumulation. Among the genotypes tested, Shubhra performed best, while Parvati the least for most of the parameters studied. Thus, combined application of 10−6 mol L−1 GA3 plus N26.8P8.94 proved best and can be recommended to exploit the linseed as a dual-purpose crop for good yield of seed and fibre.

Effects of Seed P-enrichment and Localized P-fertilizer Application on Soil-grown Wheat

We previously reported two methods of phosphorus (P) supply that improve crop growth. One is to apply P-fertilizer locally into soils and the other is seed P-enrichment by soaking seeds in P-solution. Here, we examined which of the two methods or a combination of the two is more effective for wheat grown in pots. Each method increased dry matter to a similar extent but with a different time interval. The effect of localized P-application was observed at 25 d after sowing (DAS), while that of seed-P enrichment was observed at 50 DAS. Despite the positive effects of both methods, their combination had no additive effect. At 50 DAS, the growth variations were explained by P content, which depended on root length. We therefore assume that increasing root length may be the common and biologically relevant feature of both methods and that either application alone is sufficient to achieve this effect.

Exogenous application of proline alleviates salt-induced oxidative stress in Phaseolus vulgaris L. plants

SummaryTwo field experiments on common bean (Phaseolus vulgaris L.) plants were conducted at three sites having different levels of salinity (EC = 1.84, 6.03, or 8.97 dS m–1) and considered to be low, moderate, or highly saline soil, respectively. The aim was to examine the effects of three successive exogenous applications of 5.0 mM proline, applied as foliar sprays at 20, 30, and 40 d after sowing (DAS) to each plant at each site. Bean plants were sampled 50 DAS and the effects of the proline sprays on various growth parameters, levels of photosynthetic pigments, endogenous proline, ascorbic acid, nitrate, nitrite, and mineral nutrient (P, K, Na) concentrations, and anti-oxidant enzyme activities were measured in order to understand the mechanism(s) of salt tolerance in proline-treated bean plants. Exogenous applications of 5 mM proline alleviated oxidative stress and enhanced the growth of all treated common bean plants. Proline also increased the activities of the anti-oxidant enzymes, superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD), as well as the concentrations of carotenoids, ascorbic acid, and endogenous proline. Spray applications of proline increased the concentrations of P and K+, and decreased Na+ ion concentrations, in salt-affected plants. Thus, the K+:Na+ ratio increased. Based on these findings, we recommend the use of proline as a commercial formulation to enhance plant growth and production in common bean plants grown under saline conditions.

Fluctuations in peroxidase and catalase activities of resistant and susceptible black gram (Vigna mungo (L.) Hepper) genotypes elicited by Bemisia tabaci (Gennadius) feeding

Whitefly, Bemisia tabaci (Gennadius) (Hemiptera: Aleryrodidae), is a serious pest of black gram, (Vigna mungo (L.) Hepper), an important legume pulse crop grown in north India. This research investigated the potential role of selected plant oxidative enzymes in resistance/susceptibility to whitefly in nine black gram genotypes. Oxidative enzyme activity was estimated spectrophotometrically from leaf samples collected at 30 and 50 d after sowing (DAS) from whitefly infested and uninfested plants. The enzymes showed different activity levels at different times after the infestation. The results indicated that in general, whitefly infestation increased the activities of peroxidase and decreased the catalase activity. Resistant genotypes NDU 5-7 and KU 99-20 recorded higher peroxidase and catalase activities at 30 and 50 DAS under whitefly-stress conditions as compared with non-stressed plants. The results suggest that the enhanced activities of the enzymes may contribute to bioprotection of black gram plants against B. tabaci infestation. The potential mechanisms to explain the correlation of resistance to whitefly in black gram genotypes with higher activities of oxidative enzymes are also discussed.

Heterosis of Arabidopsis hybrids between C24 and Col is associated with increased photosynthesis capacity

Arabidopsis thaliana shows hybrid vigor (heterosis) in progeny of crosses between Columbia-0 and C24 accessions. Hybrid vigor was evident as early as mature seeds and in seedlings 3 d after sowing (DAS). At 3 DAS, genes encoding chloroplast-located proteins were significantly overrepresented (187) among the 724 genes that have greater than midparent values of expression in the hybrid. Many of these genes are involved in chlorophyll biosynthesis and photosynthesis. The rate of photosynthesis was constant per unit leaf area in parents and hybrids. Larger cell sizes in the hybrids were associated with more chloroplasts per cell, more total chlorophyll, and more photosynthesis. The increased transcription of the chloroplast-targeted genes was restricted to the 3-7 DAS period. At 10 DAS, only 118 genes had expression levels different from the expected midparent value in the hybrid, and only 12 of these genes were differentially expressed at 3 DAS. The early increase in activity of genes involved in photosynthesis and the associated phenomena of increases in cell size and number through development, leading to larger leaf areas of all leaves in the hybrid, suggest a central role for increased photosynthesis in the production of the heterotic biomass. In support of this correlation, we found that an inhibitor of photosynthesis eliminated heterosis and that higher light intensities enhanced both photosynthesis and heterosis. In hybrids with low-level heterosis (Landsberg erecta x Columbia-0), chloroplast-targeted genes were not up-regulated and leaf areas were only marginally increased.

Effects of Soil Types on Phytotoxic Activity of Pretilachlor in Combination with Sunflower Leaf Extracts on Barnyardgrass (Echinochloa crus-galli)

The increasing use of synthetic chemicals for pest control in rice has become an overwhelming economical border, and more important, it could pose a serious threat of the environment. In addition, the extensive use of synthetic herbicides has been the cause for the evolution of herbicide-resistant barnyardgrass worldwide. This weed species is the most competitive weed in rice after the red rice. Thus, this study was conducted to examine the combination effects of aqueous sunflower leaf extracts with lower rate of pretilachlor on barnyardgrass emergence and growth in Marang (sandy loam) and Seberang (silt loamy) soil series under glasshouse conditions. Interestingly, the ED95values (rate that causes 95% inhibition) of pretilachlor for emergence and shoot fresh weight (SFW) of barnyardgrass were reduced by 79 and 82%, respectively, when being mixed with sunflower leaf extracts in Marang series. In contrast, the addition of sunflower leaf extracts increased ED95value of pretilachlor in Seberang series. Rice seedlings at 4 and 8 d after sowing (DAS) were found to be tolerant to this mixture treatment. However, root growth of rice seedlings were inhibited at 0 and 2 DAS. These results suggest that sunflower leaf extracts have potential to reduce rate of pretilachlor for inhibiting emergence and growth of barnyardgrass without injuring rice seedlings in rice fields depending on soil types and growth stage of rice.