Role of Selenium in Regulation of Plant Antioxidants, Chlorophyll Retention and Osmotic Adjustment under Drought Conditions: A Review

Environmental change is ascending as one of the most unpredictable issue, the effects of which are observable as rise in the onset of regular abiotic stresses like no or irregular precipitation, ascend in worldwide normal temperature, floods and so on. Among all the abiotic stresses, drought stress has become a sector of interest for decades. Drought stress can be chronic in locations with low water accessibility or irregular precipitation during the time of plant development consequently decreasing its growth and yield through its impact on plant photosynthetic rate, increased load of reactive oxygen species, changes in plant water relations and so on. A great deal of examination has been done to study the varieties of changes in the plants at the morphological, physiological and cellular level to identify the methodologies for enhancing plant drought resistance. In this regard "selenium" (Se) is considered exceptionally significant for improving plant growth and development. Spraying drought stressed plants or pre-treating the seeds with low dosage of Se have been shown to be associated with upgraded plant drought resistance. The present study is aimed to frame a review on the regulation of plant defense system, chlorophyll retention and plant water relations so as to provide comprehensive understanding into the changes caused by the application of Se which inturn are liable for improved plant drought tolerance.

The Arabidopsis gene RGO mediates cytokinin responses and increases seed yield

A novel gene, At1g77960, from Arabidopsis thaliana was characterized. At1g77960 transcripts accumulate to very high levels in plants ectopically overexpressing the Golden2-like1 (GLK1) transcription factor and is designated as a Response to GLK1 Overexpression (RGO) gene. RGO encodes a protein with domains of tandem QH and QN repeats. Transcripts and promoter GUS reporter analyses indicated that RGO is expressed in roots, leaves, stems, floral and siliques tissues but not in seeds. Expression of the RGO:YFP fusion protein demonstrated that RGO is localized to the endoplasmic reticulum. MicroRNA mediated silencing of RGO resulted in severe reductions in vegetative and root growth, delayed flowering and reduced seed yield and viability, suggesting that RGO is essential for plant development. Conversely, ectopic overexpression of RGO resulted in enhanced vegetative growth including increased axillary bud formation and a 20% higher seed yield. Stable overexpression of RGO in Brassica napus also produced a similar increase in seed yield. Cytokinin (CK) response assays including root growth, green calli formation from excised hypocotyls and chlorophyll retention during dark-induced senescence suggest that one role of RGO is to mediate CK responses in plant development. These results suggest that RGO could be a target gene for increasing crop seed yields.One-sentence summaryRGO, a novel gene from Arabidopsis, is essential for plant development, mediates CK signaling and increases seed yield in Arabidopsis and rapeseed when overexpressed.

EFFECT OF SOLAR DEHYDRATION METHOD ON PHYSICO-CHEMICAL AND SENSORY CHARACTERISTICS OF GREEN BEANS (PHASEOLUS VULGARIS)

Studies were done by different chemical treatments under solar dehydration of Green beans. The Green beans were treated by five different methods which are mentioned and the end product was underwent analysis for physico-chemical characteristics, nutritional characteristics, microbial analysis and sensory evaluation. Five treatments of different proportions with Magnesium chloride, Sodium chloride, Sodium bicarbonate and Magnesium oxide were done for solar dehydration of Green beans and (0.1% Magnesium chloride and 0.1% Sodium bicarbonate) treated Green beans were found to be good in all characteristics i.e. Physico-chemical (better chlorophyll retention) and nutritional characteristics when compared to other treatments.

Size, chlorophyll retention and protein and oil contents of grains from soybean plants grown in different spatial arrangements

The spatial arrangement of soybean plants, determined by row spacing and seeding rate, affects the intraspecific competition for water, light, and nutrients, as well as plant architecture and grain development, quality, and chemical composition. The aims of this study were to evaluate the effect of row spacing and seeding rate on the grain size produced, and the influence of these three factors on chlorophyll retention and protein and oil content in grain. Two experiments were conducted in the 2013/14 and 2014/15 growing seasons, using a 4 × 3 factorial randomized block design with three replications. Four different row spacings [20 cm (narrow row), 50 cm (conventional), 20/80 cm (twin rows) and crossed lines (50 cm)] and three seeding rates (150, 300, and 450 thousand viable seeds ha-1) were evaluated. The grains were classified by size using oblong sieves and then the effects of spatial arrangements and size of grain on the percentage of green grains and protein and oil contents were evaluated. Higher plant densities were associated with larger grain size, whereas the effects of spacing between the rows on the grain size varied between growing seasons. The arrangement in cross-rows and high plant density produced a higher percentage of green grains under weather conditions favorable to the development of this attribute. The effects of plant spatial arrangements on the contents of protein and oil in grains were variable, and it was not possible to determine whether the spatial arrangement of plants had an effect on the levels of protein and oil in grains. Larger grains had higher protein content, but oil contents were not affected by grain size.

The continuous accumulation of Na+ in detached leaf sections is associated with over-expression of NTHK1 and salt tolerance in poplar plants

Detached leaf sections (2 × 2 cm2) from transgenic poplar line 18-1 and its wild type (WT) (Populus × euramericana ‘Neva’) were used to test their salt tolerance and gene expression under controlled environment conditions. The sections from line 18-1 displayed better tolerance to NaCl stress, indicated by high chlorophyll retention and K+ content but low relative electrolyte leakage (REL). Transient overexpression of NTHK1 (Nicotiana tabacum histidine kinase 1) and V-H+-PPase was found in the detached young leaves from line 18-1 after they had been stressed for a few minutes. The activities of vacuolar-type H+-ATPase and H+-PPase in line 18-1 were boosted initially and then decreased to normal level as in unstressed leaves. After sections were stressed for 10 days, the maximal Na+ concentration in line 18-1 was much higher than that in the WT. The higher capacity for Na+ accumulation in line 18-1 may be due to stable Na+ sequestration into the vacuoles. Osmotic stress imposed little effect on REL and chlorophyll content of the sections. The capacity of detached leaf sections in NaCl solution to tolerate stress and to accumulate Na+ may be useful for identifying genotypes with good salt tolerance in poplar and other plants.

Solar Cabinet Drying of Bitter Gourd: Optimization of Pretreatments and Quality Evaluation

Response surface methodology was used to optimize the pretreatments before solar cabinet drying of bitter gourd slices (6-7 mm thick). Central composite design (CCD) was used to conduct the experiments which consisted thirteen experiments with two variables, viz., blanching time (1-5 min) and potassium metabisulfite (KMS) (0.2-0.5 %). After the pretreatments, the bitter gourd slices were dried up to 6 % (Approx.) moisture content (d.b) in solar cabinet dryer at air temperature, relative humidity and air velocity in the range 38 to 62°C, 45 to 55 % and 0.9 to 1 m/s, respectively. The responses taken were chlorophyll retention (mg/100g of dried sample) and texture (hardness) of dehydrated bitter gourd slices. The optimum process condition was found at 4.24 min blanching time and 0.49 % KMS which resulted in 20.15 mg/100g chlorophyll retention and 340.55 g hardness. Some selected quality attributes of solar cabinet dried bitter gourd slices pretreated with the optimized combination of blanching time and KMS were compared with the quality of freeze and open sun dried samples and it was found that quality of solar cabinet dried product was falling in between open sun and freeze dried products. Also, the drying data of bitter gourd slices obtained during solar cabinet, freeze and open sun drying were analyzed and drying constants as well as moisture diffusivity were calculated.

Response of soybean genotypes to the expression of green seed under temperature and water stresses

Soybeans grown under water stress associated with high temperatures during seed maturation and pre-harvest may produce green seed (GS) with expressive reduction in seed quality. The objectives of this study were to evaluate the response of different soybean cultivars grown under these stressful conditions regarding their susceptibility to GS production and to determine the chlorophyll retention levels and the chlorophyllase activity in the seeds. Seeds of four soybean cultivars [BRS 133, CD 206, MG/BR 46 (Conquista) and BRSMG 251 (Robusta)] were grown under greenhouse conditions until R5.5. At R6, the plants were transferred to phytotrons under temperature stress (from 28ºC to 36ºC) and with water stresses of 10% gravimetric moisture, no water and normal supply. Seeds were harvested at R9 when the percentage of GS and weight of 100 seeds were determined. The contents of a, b and total chlorophylls and the chlorophyllase activity were also determined. The expression of GS production under these conditions varied among cultivars: Conquista and Robusta were considered more susceptible to the production of GS compared to 'BRS 133' and 'CD 206'. These cultivars produced lower GS levels, lower chlorophyll retention and higher chlorophyllase activity compared to Robusta and Conquista. Soybean plants submitted to water and temperature stresses produced high levels of GS, which were small, light and had high chlorophyll contents and low chlorophyllase activity. The contents of a, b and total chlorophylls in GS were inversely proportional to the chlorophyllase activity.