Effect of ethylene on physiological and biochemical parameters in different crop plants - A review

A phytohormone may be defined as an organic substance other than a nutrient active in very minute amounts which is formed in certain parts of all plants and which is usually translocated to other sites, where it evokes specific biochemical, physiological and morphological responses. The gaseous plant hormone ethylene modulates many internal processes and growth responses to environmental stimuli. Ethylene is known to exert its effects by altering gene expression both at transcriptional and post-transcriptional level. Ethylene has long beenrecognized as a growth inhibitor, but evidence is accumulating that ethylene can also promote growth. Therefore, the concept of ethylene as a general growth inhibitor needs reconsideration. Different authors screened various concentrations viz. 100 ppm, 150 ppm which promotes the plant growth in groundnut, soybean, mustard, barley, pigeonpea etc. The lower concentration of ethylene (100ppm) has increased the yield by 17 percent in pigeonpea. It increased the yield by manipulating source-sink relationships and flower retention The present study highlights the various processes of growth stimulated by ethylene and its use in enhancing yield of various crop species. It could be inferred that lower concentration of ethrel sprayed at pre-flowering stage promoted the growth and yield of various crops (barley, corn, groundnut, pigeonpea, soybean etc.)

Influence of salicylic acid on biochemical parameters and antioxidant system in mashbean plants grown under salt stress conditions

Abiotic stress factors affect almost every aspect of physiology and biochemisrtry of a plant. The present study investigates the role of salicylic acid (SA) in inducing plant tolerance to salinity. The application of 0.5 mM and 1.0 mM SA to mashbean (Vigna mungo L.) plants provided protection against 30mM or 45mM NaCl stress throughelevated antioxidant system. The genotypes KUG 363, KUG 310, (salt sensitive), KUG 502 and KUG 529 (salt tolerant) along with UL 338 (as check) were subjected to salt stress. Relative leaf water content (61%) decreased under 45mM salt stress in salt tolerant genotype KUG 529 as compared to control (85%). Leaf water potential was also recorded at 50 DAS in salt tolerant genotype KUG 529 (-2.66 mpa) and in salt sensitive genotype KUG 363(-3.76 mpa) .All the genotypes showed higher accumulation of Reactive Oxygen Species under salt stress. A remarkable decrease was shown in antioxidant enzymes like catalase (179 micro mole/min/g FW) and ascorbate peroxidase (1617 n moles/min/g FW) in KUG 529 . The level of antioxidant system was enhanced catalase (184 micro mole/min/g FW) and ascorbate peroxidase (1853 n moles/min/g FW) in mashbean plants under NaCl stress following SA applications . Thus SA helped in conferring stress tolerance to mashbean plants through enhanced antioxidant system. However, tolerant genotypes responded better than sensitive ones and lower concentration of SA (0.5mM) was more effective

Physiological and biochemical response to higher temperature stress in hot pepper (Capsicum annuum L.)

The present study was conducted to evaluate the physiological and biochemical changes in some thermotolerant and thermosensitive chilli (Capsicum annuum L.) genotypes. Fourteen chilli genotypes (SL 461, PP 404, DL 161, MS 341, VR 521, PB 405, PS 403, SD 463, FL 201, AC 102, S 343, SL 462 and SL 464 along with sensitive check [Royal Wonder of bell pepper] were evaluated for heat tolerance. The observations on morpho-physiological and biochemical parameters were recorded at 45, 65, 85 and 105 days after transplanting (DAT) (high temperature period). On the basis of our studies, genotypes S 343, AC 102 and FL 201 were found to be relatively thermotolerant. However, high temperature markedly decreased the photosynthetic activity of chilli plants by decreasing the photosynthetic pigments in leaf chloroplasts of all the genotypes. The levels of ascorbic acid, total soluble sugars and total phenols increased in the leaves of all the genotypes with the maturity of the crop. Electrolyte leakage and proline content also increased with rise in temperature. Genotypes AC 102 and S 343 were able to accumulate the maximum ascorbic acid, proline, total soluble sugars and total phenols under heat stress conditions. Decrease in fruit set percent led to reduction in the total yield per plant. Maximum yield was observed in genotype S 343 followed by FL 201

Mitigation of salt stress with Azospirillium and Azotobacter inoculation in maize (Zea mays L.)

A pot experiment was designed to study the effect of Azotobacter and Azospirillum inoculation on the growth parameters (root shoot fresh weight, dry weight and length), level of enzymatic and non-enzymatic antioxidants, photosynthetic pigments, water status, level of osmolytes and metaxylem vessel elements (MVE) of maize roots under control conditions as well as under salt stress conditions (100 mM and 150 mM NaCl). The results revealed that stress conditions increased the level of antioxidants, antioxidant enzyme activities and some osmolytes like total soluble sugars and proline. On the contrary, growth parameters, total soluble proteins, photosynthetic pigments and MVE number and area were reduced under salt stress. Inoculation with Azotobacter and Azospirillum improved the growth parameters, increased the level of osmolytes, antioxidants, activities of antioxidant enzymes, photosynthetic pigments and MVE area and number, not only under control conditions but also under stress conditions. It was observed that bacteria inoculation counter acted on the harmful effects of salt stress. Therefore to conclude, inoculation of seeds with microbes before sowing in salt affected soils can mitigate the negative effects of salt stress