BackgroundSalinity is a stressful environmental factor that limits the productivity of crop plants, and roots form the major interface between plants and various abiotic stresses. Rice is a salt-sensitive crop and its polyploid shows advantages in terms of stress resistance. The objective of this study was to investigate the effects of genome duplication on rice root resistance to salt stress.ResultsBoth diploid rice (HN2026-2x and Nipponbare-2x) and their corresponding tetraploid rice (HN2026-4x and Nipponbare-4x) were cultured in half-strength Murashige and Skoog medium with 150 mM NaCl for 3 and 5 days. Accumulations of proline, soluble sugar, malondialdehyde (MDA), Na+ content, H+ (proton) flux at root tips, and the microstructure and ultrastructure in rice roots were examined. We found that tetraploid rice showed less root growth inhibition, accumulated higher proline content and lower MDA content, and exhibited a higher frequency of normal epidermal cells than diploid rice. In addition, a protective gap appeared between the cortex and pericycle cells in tetraploid rice. Next, ultrastructural analysis showed that genome duplication improved membrane, organelle, and nuclei stability. Furthermore, Na+ in tetraploid rice roots significantly decreased while root tip H+ efflux in tetraploid rice significantly increased.ConclusionsOur results suggest that genome duplication improves root resistance to salt stress, and that enhanced proton transport to the root surface may play a role in reducing Na+ entrance into the roots.

Soybean genotypes show diverse physiological responses to drought, but specific physiological traits that can be used to evaluate drought tolerance have not been identified. In the present study we investigated physiological traits of soybean genotypes under progressive soil drying and rewetting, using a treatment mimicking field conditions. After a preliminary study with eight soybean genotypes, two drought-tolerant genotypes and one susceptible genotype were grown in the greenhouse and subjected to water restriction. Leaf expansion rate, gas exchange, water relation parameters, total chlorophyll (Chl), proline contents of leaves, and root xylem pH were monitored in a time course, and plant growth and root traits were measured at the end of the stress cycle. Drought-tolerant genotypes maintained higher leaf expansion rate, net photosynthetic rate (P n ), Chl content, instantaneous water use efficiency (WUEi), % relative water content (RWC), water potential (ψ w ), and turgor potential (ψ p ) during progressive soil drying and subsequent rewetting than the susceptible genotypes. By contrast, stomatal conductance (g s ) and transpiration rate (T r ) of tolerant genotypes declined faster owing to dehydration and recovered more sharply after rehydration than the same parameters in susceptible ones. Water stress caused a significant increase in leaf proline level and root xylem sap pH of both genotypes but tolerant genotypes recovered to pre-stress levels more quickly after rehydration. Tolerant genotypes also produced longer roots with higher dry mass than susceptible genotypes. We conclude that rapid perception and adjustment in response to soil drying and rewetting as well as the maintenance of relatively high P n , %RWC, and root growth constitute the mechanisms by which drought-tolerant soybean genotypes cope with water stress.

Abstract:The impact of chemical farming and the negative consequences on the environment and human health in Bangladesh are on the rise. Organic farming is gaining attention and increasing globally because it is eco-friendly, safe and has benefits for human health. A field study was conducted at the horticulture farm of Bangladesh Agricultural University (BAU), Mymensingh, to evaluate the growth and yield performance of cabbage cv. Atlas-70 using organic and inorganic fertilizers in various plant spacing arrangements. Two factor experiments were conducted on plant spacings of 60 cm × 40 cm (S 1 ), 60 cm × 50 cm (S 2 ) and 60 cm × 60 cm (S 3 ) and fertilizers vermicompost (T 1 ), biogen (T 2 ), integrated plant nutrient system (IPNS) Organic ( 2 /3) + inorganic ( 1 /3) (T 3 ) and inorganic (T 4 ). IPNS (T 3 ) application increased the marketable yield (54.77 t·ha −1 ) of cabbage. The highest marketable yield (48.75 t·ha −1 ) was obtained with a plant spacing of 60 cm × 40 cm (S 1 ). No significant variation was found in plant spacings S 1 and S 2 . The treatment combination of S 2 T 3 recorded the highest plant height (37.81 cm), plant spread (47.75 cm), cabbage head (21.80 cm), stem length (12.31 cm), thickness of the cabbage head (12.53 cm) and marketable yield (65.0 t·ha −1 ). The results suggest that IPNS (T 3 ) combining organic and inorganic fertilizer applications with a 60 cm × 50 cm spacing (S 2 T 3 ) increases the yield performance of cabbage.

Drought stress effects on leaf gas exchange, cell membrane stability, seed yield and yield attributes of synthesized Brassica napus L. cv, Bangla kale and Bangla cabbage were compared. Drought stress treatments were imposed at early vegetative, late vegetative and flowering stages by withholding watering. Bangla cabbage produced greater pods/plant, larger seed size, greater total dry matter/plant, seeds/pot, and ] 7 % greater yield than Bangla kale. The seed yield in plants stressed at early vegetative, late vegetative and flowering stages were 59. 74, 88 % lower respectively, than watered plants. Drought stress reduced leaf photosynthesis by 67 to 97 %. Bangla cabbage had 68 % greater photosynthesis and 56% greater stomatal conductance than Bangla kale under stress at tlowering stage. Leaf temperature was 1 to 2 C higher in stressed plants than watered plants. The cell membrane stability (CMS) increased up to 83 % at flowering stage under stress compared to 21 % under watered conditions. Although Bangla cabbage had high seed yield, yield attributes and photosynthesis under stressed conditions at flowering stage, its CMS values were lower than those of Bangla kale.

Four orange fleshed sweet potato (OFSP) genotypes viz., CIP 194513.15, CIP 194515.15 The maximum dry matter (29.83%) was obtained in H 6 /07 while the minimum dry matter (17.61%) was obtained in CIP 441132. Among the tested genotypes the highest (approximately) Vitamin A (919.2 µg/100 g RE, FW) was recorded in CIP 440267.2, which had red skin and latex absent flesh and the lowest was (approximately) in H 6 /07 (Vit A 0.0 µg/100 g RE, FW). The results of the present study indicated that CIP 440267.2 is suitable among the OFSP genotypes for cultivation in Bangladesh on the basis of yield and quality mainly carotinous.