Leaf SPAD Research Articles

Evaluation of cowpea for drought tolerance at seedling stage

Cowpea is a health-promoting diploid legume species [Vigna unguiculata (L.) Walp., 2n = 2x = 22]. The annual cowpea production is 5.4 million tons of dry seed globally. Despite the fact that cowpea is one of the most drought-tolerant crops, some genotypes with excellent agronomic traits such as high yield under sufficient water supplies have been reported to be highly drought-susceptible, thus still requiring the need for breeding drought-tolerant cowpea genotypes. Therefore, the objectives of this study were to evaluate drought tolerance in cowpea at seedling stage and to identify drought-tolerant cowpea genotypes. In this study, a total of 331 cowpea genotypes were evaluated for drought tolerance at seedling stage. The experiment was conducted in a greenhouse and repeated 3 times. Drought tolerance phenotyping was conducted using a previously described methodology and a total of 11 traits were analyzed. The experiment was validated by the use of drought-tolerant and susceptible controls. Results showed that: (1) a large variation in the evaluated traits for drought tolerance was identified among the 331 cowpea genotypes, (2) a high correlation was found for traits such as plant greenness score and tolerance to trifoliate leaf chlorosis under drought stress (r = 0.8), whereas no linear correlation was found for traits such as tolerance to trifoliate leaf chlorosis and unifoliate leaf SPAD chlorophyll under non-drought stress (r = 0.0), (3) a total of 21 genotypes were found to be drought-tolerant across different traits, and (4) country of origins could impact drought tolerance in cowpea. The top performing genotypes were repeated using an independent experiment to further validate the data. The results from this study would be of interest in breeding programs aiming at improving drought tolerance in cowpea.

Effects of nitrogen fertilizer rates and waterlogging on leaf physiological characteristics and grain yield of maize

ABSTRACT Nitrogen fertilizer supply and use play a vital role in determining crop growth and yield. However, the effects of nitrogen fertilizer levels on plant growth under waterlogging conditions remain elusive. The objective of this study was to investigate the effects of nitrogen fertilizer rates (0, 90, 180, 270, and 360 kg N ha−1, designated N0, N1, N2, N3, and N4, respectively) on leaf physiological characteristics and grain yield of maize (Zea mays L.) under two water regimes (WW or well-watered through the maize grown season and WL or waterlogged for six days at the sixth-leaf stage). Overall, in comparison to WW, WL treatment showed a reduction in the following traits, at all nitrogen rates: plant height, leaf area index, SPAD value, superoxide dismutase, peroxidase, and catalase activity, net photosynthetic rate (P n), transpiration rate, stomatal conductance, ears per ha, kernels per ear, 1,000-kernel weight, and grain yield. Moreover, the majority of the above parameters increased with the increase in nitrogen application rate under WL, as a result of the enhanced available nitrogen content at higher nitrogen application rates. Therefore, increasing supply levels of nitrogen fertilizer could improve antioxidant enzyme activity and P n, consequently producing increased maize grain yield under waterlogged conditions.

Control effects of different herbicides on weeds as well as their effects on growth and deve-lopment of broomcorn millet

Selecting a herbicide suitable for broomcorn millet is a key issue in high efficiency and safe production of broomcorn millet and ecological environment improvement. We compared the control effects of 22 different herbicides on weeds as wells as their effects on growth and development of glutinous millet (Yumi 2) in the field. The results showed that, 1) soil applied Goyou, Butachlor, atrazine, and Benzipram, and stem- and leaf-applied WP mixture of tribenuron-methyl·carfentrazone-ethyl·MCPA-Na, Sigma Broad, Tengjing, Taoshi·Youxian and Kuofei had little phytotoxi-city, with broomcorn millet seedlings growing normally, and the other herbicides had phytotoxicities on broomcorn millet. 2) All the herbicides controlled weeds in the field to some extent, with better performance of soil applied herbicides than the stem- and leaf-applied ones, and affected plant height, functional leaf SPAD and spike weight per plant of broomcorn millet. 3) Compared with manual weeding, all herbicides reduced yields of glutinous millet. Compared with no herbicides application, some herbicides had yield-increasing effects. Among the soil applied herbicides, Go-you, Butachlor, atrazine, and Benzipram performed better in weeding control, increasing the yield of broomcorn millet by more than 60% compared with no herbicide control. Among the stem- and leaf-applied herbicides, Sigma Broad and WP mixture of tribenuron-methyl·carfentrazone-ethyl·MCPA-Na performed better in weeding control, increasing the yield of glutinous millet by more than 50% compared with no herbicide control. Therefore, applying 38% atrazine or 44% Monosulfuron to soil before the emergence of broomcorn millet, or stem- and leaf-applied 3.6% mesosulfuron-methyl or 55% WP mixture of tribenuron-methyl·carfentrazone-ethyl·MCPA-Na after the emergence of broomcorn millet, performed better in weeding control and with limited effects on the growth and development of broomcorn millet.

Effect of moisture stress on physiological mechanisms in drought tolerance in selected genotypes of groundnut (Arachis hypogaea L.)

Eight groundnut genotypes of including four released and pre-released genotypes were evaluated for moisture stress at pegging (M2) and pod development (M3) stage stress situations with control (M1) during post-rainy season (Nov-April), 2018-19 at University of Agricultural Sciences, Dharwad and Karnataka, India. The drought stress was imposed by with holding irrigation at 40-80 DAS (M2) and 80 DAS-harvest (M3). Observations were recorded for physiological parameters like leaf area, SPAD readings, chlorophyll content, stomatal frequency, photosynthetic rate and pod yield per plant. Among the selected genotypes, GPBD-4, Dh-257 and Dh-256 are considered as drought tolerant genotypes at both the stress levels based on lesser reduction in leaf area, optimum chlorophyll content and photosynthetic rate, less leaf folding and by these adaptations recorded reduced reduction in pod yield over control. Genotypes, Dh-86 and TMV-2 affected severely by drought at both the stages. But higher effect was observed under pod developmental stage stress.

Production and quality of eucalyptus mini-cuttings using kaolin-based particle films

Considering the expansion of forest plantations over the Brazilian territory and the imminent increase in air temperatures due to global warming, the search for technologies that ensure high levels of productivity and high quality plants in clonal nurseries is essential. Applying kaolin-based particle films (KBPF) has been used as a physical barrier to reduce the negative effects of excessive solar radiation and adverse temperatures. The effects of KBPF on production and physiological quality of eucalyptus mini-cuttings were evaluated during two different seasons. A randomized block design was used, consisting of five treatments and four replications. Five concentrations (0, 3%, 5%, 7%, and 10%) were tested here and six weekly replicates of each concentration was applied. The different kaolin concentrations and seasonal variations resulted in a quadratic response of the leaf SPAD reading during both daily evaluation periods. KBPF applications resulted in a quadratic response of photochemical efficiency in the morning period, and an increasing specific leaf weight linear response, and during the dry season, the different kaolin concentrations resulted in a bud length quadratic response. The results indicated that the kaolin application maintained the production and yield index statistically equal between weekly KBPF applications, improving photochemical efficiency, leaf thickness, SPAD reading, and bud length. The use of KBPF could reduce the intervals between collections of mini-cuttings and increase nursery yields in environments that present high temperatures.

Leaf Characteristics at Recovery Stage Affect Seed Oil and Protein Content Under the Interactive Effects of Nitrogen and Waterlogging in Rapeseed

Four nitrogen rates (0, 90, 180, and 270 kg ha−1) were applied to the waterlogging-tolerant variety ZS 9 and the sensitive variety GH01. Seedlings with five leaves were waterlogged for 0 (control) or 10 days to investigate the effects of nitrogen on the quality of waterlogged rapeseed. Compared with controls, the seed oil content of waterlogged rapeseed increased slightly in GH01 and significantly in ZS 9 with nitrogen application, which can be explained by the following. (1) after waterlogging, the biomass distribution in roots and leaves of ZS 9 decreased, which alleviated physiological water shortage. Conversely, biomass distribution in roots of GH01 increased, which was not synchronized with the leaf biomass change. (2) After waterlogging at 90–270 kg N ha−1, the leaf number at bolting and flowering was increased in ZS 9 but decreased in GH01 compared with the control. The decrease in leaf area and SPAD value were greater for GH01 after waterlogging, which limited photosynthesis. (3) The leaf soluble protein at bolting was highest in ZS 9 and lowest in GH01. The sensitive variety showed poor growth. The inhibition of seed protein synthesis resulted in an increase in the oil content of waterlogged rapeseed with nitrogen. The seed oil of the waterlogging-tolerant variety was most significantly negatively correlated with leaf soluble protein content at the flowering stage, while the protein content showed the opposite correlation. The seed oil of the waterlogging-sensitive variety was most significantly negatively correlated with the number of leaves at the bolting and flowering stage, while the seed protein content had opposite correlations.

5-Aminolevulinic Acid Lessened Growth Suppression in Snap Bean (Phaseolus vulgaris L.) Exposed to Shallow Water Table

Shallow water table (SWT) is an acute problem in cultivating vegetables at riparian wetland during transitional period from dry to rainy season. SWT limits volume of aerobic rhizosphere and reduces oxygen availability. Meanwhile, 5-aminolevulinic acid (ALA) has been known for its effectiveness in offsetting negative effects of abiotic stresses. The aim of this study was to evaluate effectiveness of ALA application at pre- or during continuous 20-day SWT exposure in snap bean. SWT exposures were set at depth of 5 cm (SWT-5), 10 cm (SWT-10) and 15 cm (SWT-15) below substrate surface. ALA was applied at 4 days before SWT initiation (14 DAP), mid of SWT exposure period (28 DAP), or at end of SWT exposure (38 DAP). Results of this study indicated that SWT exposure affected growth of shoots and roots, leaf water status, proline content, and SPAD value in snap bean plant. Shallowest water table (SWT-5) caused the most severe effects. Effectiveness of ALA application was depended on time difference between ALA application and onset of SWT exposure. ALA application did not significantly improve recovery of snap bean plants after SWT exposure was terminated.

Using Light Quality for Growth Control of Cucumber Seedlings in Closed-Type Plant Production System.

During seedling production, growth control of seedlings is an important problem because the overgrowth of seedlings causes a decrease of seedling quality and has disadvantages after transplanting. In this study, we aim to evaluate the possibility of replacing chemical plant growth regulators using light quality in a closed-type plant production system (CPPS) for cucumber seedling production. We used various light treatments, such as monochromatic or combined red (R) and blue (B), and combined R and B with UV-A or Far-red (Fr) light, to compare with a chemical plant growth regulator conventionally using in nursery farms. The combined R and B treatment decreased stem elongation and increased dry matter and compactness. UV-A treatment increased compactness but did not significantly affect the stem elongation or dry matter. Fr increased stem elongation and stem diameter and decreased compactness and dry matter. In leaf growth, combined R and B treatments and UV-A treatments increased leaf area, specific leaf weight, and SPAD value, and decreased leaf shape index. Fr treatments increased leaf area and leaf shape index and decreased specific leaf weight (SLW) and SPAD values. Cucumber seedlings have many different morphological changes, and R5B5 light quality was more effective in growth control due to higher compactness than chemical plant growth regulators. Also, R5B5 light quality has increased seedling quality, such as dry matter and SLW compared with fluorescent lamps. Thus, the use of light quality is a possible alternative to a chemical plant growth regulator.

Effects of urea mixed with nitrapyrin on leaf photosynthetic and senescence characteristics of summer maize (Zea mays L.) waterlogged in the field

Waterlogging is one of the major abiotic stresses in agricultural crop production. However, the application of 2-chloro-6-(trichloromethyl) pyridine (nitrapyrin) can effectually mitigate the losses of nitrogen efficiency and grain yield of summer maize induced by waterlogging. In order to explore its role to alleviate waterlogging stress on leaf antioxidative system and photosynthetic characteristics of summer maize, a field experiment was executed to research effects of nitrapyrin application on leaf photosynthetic and senescent characteristics of waterlogged summer maize Denghai 605 (DH605) and Zhengdan 958 (ZD958). Experimental treatments consisted of waterlogging treatment that was applying only urea (WL), waterlogging treatment that was applying urea mixing with nitrapyrin (WL-N), and no waterlogging treatment that was only applying urea (NWL). Results showed that WL significantly decreased leaf area index (LAI), SPAD, photosynthetic rate (Pn), and protective enzyme activities, accelerated leaf aging, eventually led to a remarkable yield reduction by 38 and 42% for DH605 and ZD958, respectively, compared to NWL. However, the application of nitrapyrin was useful for relieving waterlogging damages on leaf photosynthetic ability. LAI, SPAD and Pn of WL-N for DH605 were 10, 19 and 12–24% higher, and for ZD958 were 12, 23 and 7–25% higher, compared to those of WL, respectively. Moreover, application of nitrapyrin effectually relieved waterlogging losses on antioxidative enzyme activities. Leaf superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) activities of WL-N were averagely increased by 24, 15 and 30%, respectively, while malondialdehyde (MDA) content was averagely decreased by 13%, compared to those of WL. Visibly, nitrapyrin application could improve leaf photosynthetic characteristics and retard leaf aging induced by waterlogging, thereby leading to a yield increase of waterlogged maize.

Silicon beneficial effects on yield, fruit quality and shelf-life of strawberries grown in different culture substrates under different iron status

The silicon application either as foliar or to the radicular system of strawberry plants was investigated. Fortuna strawberry plants were grown in two different substrates (coconut fibre and organic substrate) under optimal (20 μM) or low (5 μM) iron (Fe) conditions. During the study, crop parameters including leaf area, SPAD and fruit yield were measured. At harvest, fruit quality and post-harvest shelf-life were evaluated. Results indicated that “Fortuna” strawberries plants had a poor development in coconut fibre and excellent growth and yield in the organic substrate. In the coconut fibre substrate, no differences in foliar area, fruit diameter, colour, pH and shelf-life were observed related to the Si addition under deficient Fe conditions, but an increased in weight and the firmness of the fruits, as well as in fructose content was shown. However, when 20 μM Fe were supplied, the root application of Si significantly increases: protein, mineral and sugar content, as well as fruit shelf-life by an average of 1.5 days. Likewise, the radicular silicon application to the organic substrate considerably improved yield, fruit diameter, fruit weight, glucose and fructose fruit content and the fruit shelf-life without causing distinguishable chemical or physicochemical changes. In summary, Si application to Fortuna strawberries through the roots could be a good solution to increase fruit quality and yield and to increase benefits from the agronomical point of view. Further studies in other strawberry varieties and dose rates will allow knowing with better precision how the radicular application of silicon contributes to yield and fruit shelf-life.

Effects of seeding pattern and phosphorus application on population structure, photosynthe-tic characteristics and yield of winter wheat

Under Xinjiang winter wheat seeding pattern, in order to sort out proper phosphorus application (PA) and find out the effects and mechanism of PA on population structure, photosynthesis characteristics and yield and provide reliable evidence for PA management of winter wheat, we arranged a two-factor complete split-plot design of wheat variety "Xindong 22". The main area consisted of two seeding ways: drill seeding pattern (D) and uniform seeding pattern (U), while in the sub-area there were four levels of PA(P2O5): 0, 60, 120, and 180 kg·hm-2(represented by P0, P60, P120 and P180 for those treatments, respectively). The results showed that the earbearing percentage in U was 15.9% higher than that in D, and the other features (PAR interception rate, extinction coefficient, leaf area index, SPAD and photosynthetic parameters) were more optimal in 120 kg·hm-2 treatment. Our results showed that the 120 kg·hm-2 treatment in U would be the optimal option with respect to population structure, photosynthetic characteristics, and yield.

Effect of integrated agronomic managements on leaf growth and endogenous hormone content of summer maize

<p indent=0mm>The leaves are the main place of photosynthesis directly related to the nutritional status, dry matter accumulation and yield formation of maize plants. The experiment was conducted using summer maize hybrid Zhengdan 958 with treatments of T1: local conventional cultivation practices; T2: based on T1, increasing planting density, delaying harvesting time, decreasing fertilizer application, and changing fertilization time; T3: based on T2, further increasing planting density, and further increasing fertilizer rate; T4: based on T3, decreasing planting density and the amount of fertilizer; and nitrogen treatments of N0, N1, N2, and N3, with 0, 129.0, 184.5, and <sc>300.0 kg N</sc> hm^-2, respectively. The contents of IAA, ZR, and GA₃ decreased and the content of ABA increased, resulting in the decreases of SPAD, leaf area index (LAI) and specific leaf mass, when nitrogen application was not enough. And the contents of IAA, ZR, and GA₃ increased, and ABA content decreased, and LAI, SPAD and dry matter accumulation per plant increased significantly with increasing nitrogen application. Integrated agronomic management practices could regulate the content of endogenous hormones in leaves. In T4 treatment, IAA, ZR, and GA₃ contents increased by 23.1%, 9.8%, and 14.7%, the ABA content decreased by 12.4%, resulting in a suitable LAI; SPAD and final dry matter accumulation per plant were by 4.2% and 12.6% higher, respectively, than those in T1 treatment. Integrated agronomic managements could coordinate endogenous hormone contents, increase leaf SPAD and specific leaf mass, and be beneficial to dry matter accumulation per plant under the condition of reducing nitrogen application combining with optimal agronomic managements, which might be one of the important reasons for increasing summer maize yield.

Growth Characteristics and Fruit Quality of Chili Pepper under Higher Electrical Conductivity of Nutrient Solution Induced by Various Salts

Salinity as a global challenge is a very complex issue in agricultural food production. In this study, the growth characteristics of chili pepper (Capsicum annuum var. crusader) were evaluated under higher Electrical Conductivity (EC) (5 dS/m) induced by NaCl, KCl, K₂SO₄ or “All Nutrients” of Hoagland nutrient solution. The standard Hoagland solution (with EC 1.8 dS/m) was used as the control. The results showed that EC5 induced by NaCl resulted in the most negative effects on growth, yield and fruit quality parameters. Application of KCl (to induce EC5) also resulted in some reduction in growth parameters. However, application of K₂SO₄ and particularly “All Nutrients” (to induce EC5) resulted in better growth characteristics compared to plants treated with NaCl or KCl salts. There was a significant reduction in growth and fruit quality traits including plant height, leaf SPAD value, fresh and dry weights of shoots and roots, fruit fresh yield, fruit total soluble solids (TSS) and vitamin C content by NaCl and to lesser extent by KCl. However, there was no significant reduction in these traits by “All Nutrients” and for some traits by K₂SO₄ application compared to control plants.

Evaluating Peat Substrates Amended with Pine Wood Fiber for Nitrogen Immobilization and Effects on Plant Performance with Container-grown Petunia

Pine (Pinus sp.) wood products have potential to immobilize fertilizer nitrogen (N) and influence plant growth when used in soilless substrates for the production of containerized floriculture crops. Peat substrate was amended with (by volume) 30% pine wood fiber (peat:fiber) during a production phase with fertigation and a simulated consumer retail phase with clear-water irrigation using container-grown ‘Supertunia Vista Bubblegum’ petunia (Petunia ×hybrida). The objective was to evaluate substrate effects on substrate and plant tissue nutrient level and plant growth, with an emphasis on evaluating N immobilization from wood product amendments. Substrates consisting of peat amended with hammer-milled pine wood (peat:wood) or coconut (Cocos nucifera) coir (peat:coir) were used for comparison, and a 100% peat substrate (peat) served as a control. In Expt. 1, amending peat with pine wood fiber had no effect on leaf SPAD chlorophyll index, shoot growth, plant height and width, substrate N, or percent shoot tissue N at the end-of-production. In Expt. 2, plants grown in peat:fiber had reduced flower number, plant height and width, and shoot growth compared with plants grown in the 100% peat control. However, petunia grown in peat:fiber substrates maintained dark-green foliage with high leaf SPAD chlorophyll index values (≥44.4) and ≥45 flowers/plant, and therefore were considered marketable plants. During the production phase in both Expts. 1 and 2, N concentrations remained within the target range for petunia in both the shoot tissue and root-zone for all substrates. In addition, there was no statistical evidence of N immobilization for any substrate blend for either of the N drawdown procedures. In both Expts. 1 and 2, root-zone nutrients became depleted during the consumer phase when irrigation was with clear water (no fertilizer), and petunia developed uniform symptoms of leaf chlorosis and N deficiency. Results of this study indicate that peat amended with 30% pine wood fiber, hammer-milled pine wood, and coconut can be used for production of containerized petunia with minimal effects on plant growth or need to adjust the fertilizer program. However, increasing pine wood to &gt;30% of the substrate volume may require growers to increase fertilization and adjust irrigation practices to compensate for greater risk of N immobilization and changes in substrate physical properties.

Leaf photosynthesis and stomatal conductance acclimate to elevated [CO2] and temperature thus increasing dry matter productivity in a double rice cropping system

Changes in atmospheric CO2 concentration ([CO2]) and temperature have impacts on leaf photosynthesis (Anet) and stomatal conductance (Gs) of rice, which strongly affect dry matter productivity. Understanding of the acclimation responses of Anet and Gs under elevated [CO2] and/or temperature is limited. A field experiment of double rice (early rice-late rice rotation) was conducted using open-top chambers from 2013 to 2016 in Hubei Province, Central China, with two levels of [CO2] (ambient, ambient + 60 μmol mol−1) and two levels of temperature (ambient, ambient + 2°C). Averaging across the four-year experiment, elevated [CO2] and elevated temperature increased Anet by 2.4 %–9.4 % and 2.4 %–10.7 %, respectively at pre-heading stages. A positive interaction was observed between elevated [CO2] and temperature in early rice which further increased Anet, while the interaction was not additive in late rice. Elevated [CO2] caused lower Gs and partly offset the stimulation of elevated temperature on Gs at tillering and jointing. At post-heading stages, photosynthetic acclimation to elevated [CO2] was observed as the stimulation of Anet was not continued. Elevated temperature decreased Anet by 1.7 %–16.6 % and further accelerated photosynthetic down-regulation by elevated [CO2]. Warming reduced Gs at milking and maturity in early rice because of high ambient temperature, which resulted in stomatal limitation to photosynthesis, but its effects on Gs in late rice were positive because the ambient temperature was low. Generally, Gs acclimated to warming and CO2 enrichment in parallel with Anet when there were no environmental constraints. Earlier leaf senescence, decreased leaf SPAD, lower seed-setting rate or larger sink capacity caused by elevated [CO2] and/or temperature might directly or indirectly explain the down-regulation on photosynthesis after heading. Our results show that warming alters the acclimation of leaf photosynthesis and stomatal conductance to CO2 enrichment and the combined effects differ between growth stages, and indicate that co-elevation of [CO2] and temperature may increase dry matter productivity in the Chinese double rice cropping system.

Optimum Water and Fertilizer Management for Better Growth and Resource Use Efficiency of Rapeseed in Rainy and Drought Seasons

Optimum water–fertilizer management in rainfed agriculture is an important factor in improving crop productivity and the ecological environment under fluctuating climate conditions, especially in Southwest China, where seasonal drought and waterlogging occur frequently. In order to investigate the effects of different cultivation technologies on growth and the water and fertilizer use efficiency of rapeseed (Brassica napus L.), a two-year field study was conducted in rainy (2016–2017) and drought (2017–2018) seasons which included three cultivation patterns: (1) conventional flat planting (FP); (2) straw mulching (SM); (3) ridge-furrow rainfall harvesting system (RF), and three fertilization patterns: (1) conventional fertilization (CF); (2) reduced slow-release fertilizer (SR); and (3) no fertilizer as a control treatment. The results indicated that the yield and its composition values were lower in the rainy year than in the seasonal dry year. The single water-saving technology had no significant effect on yield increase when seasonal drought occurred. The two technologies (SM + SR and RF + SR) improved the height, leaf SPAD value and dry matter of the rapeseed and adjusted the root–shoot ratio under two different climate conditions. In the rainy season, these technologies reduced the loss of nutrients, while in the seasonal drought year, it increased the soil moisture. The SM + SR and RF + SR increased the yield of rapeseed by 7.71% and 29.93% and enhanced oil content by 4.64% and 7.91%, respectively, compared with the local cultivation pattern. Meanwhile, these treatments decreased the total water consumption during whole growth stages and promoted water use efficiency by 14.84% and 28.71%, respectively. The combination of SM + SR and RF + SR also increased the accumulation of N, P, and K and significantly promoted the utilization efficiency of fertilizer. In the future, the adverse effects of environmental factors could be relieved, and the goal of cost savings and increasing efficiency could be achieved by adopting the optimal cultivation technologies in rapeseed production of Southwest China.

Effect of Light Simplified Cultivation Mode on Growth and Yield of Rice under Straw Returning Condition

In order to study the application of light and simplified cultivation mode in straw returning field. In the experiment, two treatments of straw returning and non-straw returning were used under the light simplified cultivation mode, and the differences of tiller number, dry matter accumulation, leaf area index, chlorophyll and yield were studied. Field cultivation experiments were carried out with Jihong 9 and Jinongda 138. The results showed that the yields of Jihong 9 and Jinongda138 straw returning to the field under the light and simplified cultivation mode were 2.00% and 3.63% higher than those under the non-straw returning mode. The total grain number in the yield components increased by 3.35% and 11.60% respectively. Dry matter increased by 19.70% and 7.66% in mature period. The leaf area index (LAI) and SPAD value in the later period of straw returning were higher than those in the non-straw returning, and the number of effective tillers was lower. Light and simplified cultivation can be used as a new mode of rice high-yield cultivation under straw returning, which improves the total grain number, leaf area index, SPAD value and dry matter in the later stage, and increases rice yield. The yield advantage of Jinongda 138 under straw returning (SJ138) is more significant.

Effectiveness of different methods of salicylic acid application on growth characteristics of tomato seedlings under salinity

BackgroundSoil salinity is a real challenge in nowadays crop production in many regions. Various strategies have been applied to increase plant salinity tolerance. Salicylic acid (SA) frequently has been reported to increase plant salinity tolerance; however, the comparative efficiency of soil (root) or foliar application of SA has not been well tested yet. In this study, the effects of root or leaf pretreatment, and leaf treatment with 100 mg L−1 salicylic acid were evaluated on growth characteristics of tomato seedlings (Solanum lycopersicum Mill) under salinity stress. The plants were grown 3 weeks in sand that were fed with Hoagland nutrient solution with or without 100 mM NaCl.ResultsThe results showed that salinity significantly reduced tomato seedling growth and traits of plant height, leaf area, shoot fresh weight, and nutrient concentration of potassium, calcium, iron and zinc compared to control plants. However, leaf SPAD value, root fresh and dry weights, leaf concentration of sodium, proline and soluble sugars were significantly increased under 100 mM NaCl salinity compared to control plants. Application of salicylic acid particularly by foliar pretreatment increased the tomato plant growth and those traits that were reduced by NaCl salinity. Application of SA, particularly foliar pretreatment, also increased the root fresh and dry weights, leaf proline and soluble sugars concentrations as compared with salinity alone. Foliar SA pretreatment significantly increased leaf K and Fe concentrations, whereas leaf Ca was significantly increased by either root or leaf pretreatment with SA under salinity.ConclusionThe results indicate that the most to least effective method of SA application was leaf pretreatment, root pretreatment and leaf treatment, respectively, to recover the reduced growth parameters of tomato plant under salinity stress.

Yield and Physiological Response of Common Bean in Three Semi-Commercial Farmers’ Fields in Limpopo Province

Despite the importance of common bean (Phaseolus vulgaris) in human nutrition, its production in developing countries is far below consumption rates. A study was established to understand the yield performance and physiological response of common bean under three farmers’ field in the Limpopo Province. The results revealed significant variation in grain yield and biomass between the locations. Physiological parameters such as the Normalised Difference Vegetation Index (NDVI), Leaf Area Index (LAI), SPAD value and leaf gas exchanges were strongly influenced by the location, the crop growth stage and crop management. Dry bean crop performance was significantly lower at Masemola. Grain yield at Masemola was 30% less than that achieved at Dalmada and Mokopane. NDVI and LAI were also consistently lower at Masemola when compared to the other locations. This study revealed that poor yields by emerging farmers in dry areas are due to poor agronomic and irrigation management.

Physiological traits reveal potential for identification of drought tolerant mungbean [Vigna radiata (L.) Wilczek] genotypes under moderate soil-moisture deficit

Canopy temperature is an important physiological trait used for screening drought tolerance in several crop plants. Mungbean being often exposed to post-flowering drought,we evaluated a set of 48 genotypes for variability in post-flowering canopy temperature and its association with root traits and other physiological parameters contributing to drought tolerance under soil-moisture deficit stress conditions. Overall, canopy temperature depression revealed significant association with seed yield. Root traits like number of lateral branches and dry root weight exhibited significant negative correlation with canopy temperature. Leaf SPAD readings were positively associated with grain yield and most of the high SPAD genotypes maintained hot canopies under drought. Some genotypes with contrasting variation in SPAD levels (DMG-1050 and SML-1628) maintained their photosystem PSII health at par. Moreover, cool canopy was no guarantee for better PSII health or vice versa. This study identified some cool canopy genotypes (VC-6173-C, IC-325770 and ML-2082) and a genotype (DMG-1050) with novel trait combinations like high SPAD and better PSII health despite high canopy temperature which can be used as donors in mungbean breeding programs. Present study explores genetic variation in these adaptation traits contributing to plant performance under soil-moisture deficit stress conditions and potential of physiological breeding approaches for genetic enhancement of this legume crop.