Growth and Physiological Responses ofPhaseolusSpecies to Salinity Stress

Abstract

This paper reports the changes on growth, photosynthesis, water relations, soluble carbohydrate, and ion accumulation, for two salt-tolerant and two salt-sensitive Phaseolus species grown under increasing salinity (0, 60 and 90 mM NaCl). After 20 days exposure to salt, biomass was reduced in all species to a similar extent (about 56%), with the effect of salinity on relative growth rate (RGR) confined largely to the first week. RGR of salt-tolerant species was reduced by salinity due to leaf area ratio (LAR) reduction rather than a decline in photosynthetic capacity, whereas unit leaf rate and LAR were the key factors in determining RGR on salt-sensitive species. Photosynthetic rate and stomatal conductance decreased gradually with salinity, showing significant reductions only in salt-sensitive species at the highest salt level. There was little difference between species in the effect of salinity on water relations, as indicated by their positive turgor. Osmotic adjustment occurred in all species and depended on higher K + , Na + , and Cl − accumulation. Despite some changes in soluble carbohydrate accumulation induced by salt stress, no consistent contributions in osmotic adjustment could be found in this study. Therefore, we suggest that tolerance to salt stress is largely unrelated to carbohydrate accumulation in Phaseolus species.

Growth Responses and Leaf Antioxidant Metabolism of Grass Pea (Lathyrus sativus L.) Genotypes under Salinity Stress

“…Growing evidences indicate that abnormal accumulation of Na + and/or K + deficiency severely disrupts photosynthetic capability and impeded translocation of photosynthates from leaves into sink organs [36,57,63], and might be one of the prime reasons for reduction in photosynthetic capacity during salt-sensitivity of the present genotypes. In salt-sensitive Phaseolus species, K + deficiency combined with salt stress induced a reduction in CO 2 photo assimilation and stomata closure [62]. Similar situation was encountered in salt-sensitive genotypes and mutant lines of grass pea experiencing different NaCl-treatment regimes [39,41,55].…”

“…Excessive accumulation of Na + in leaves has been considered highly harmful for normal metabolism of plant, and tolerant genotype has the capacity of successful salt exclusion [13,36]. Salt stress also impairs K + uptake of plants, and it has been suggested that K + deficiency might be a contributing factor to salt-induced growth inhibition through induction of oxidative stress and related cell damage [57,61,62]. The K + : Na + ratio has been used as a discriminating factor between tolerant and sensitive genotypes with greater capacity of former to block or reduce the uptake or exclude the excess amount of Na + and associated increase in K + content [36].…”

“…The result indicated that early surge in Na + accumulation and low K + : Na + ratio may be detrimental to vegetative growth but its normal (control like) level is crucial in reproductive stages to maintain flowering and subsequent grain-filling stage under salt-exposure. Normal (control like) concentration of K + and K + : Na + ratio at 30 DAC and also at 60 DAC in these four genotypes might be orchestrated through a compensation over time, presumably through translocation of K + from roots and stems to leaves [61], a sustained acquisition despite appreciable overall Na + uptake [1,62], a high K + selectivity and/or K + /Na + exchange across the plasmalemma of the root epidermis [34,39,57]. The maintenance of higher leaf K + concentrations and K + : Na + ratio in the present grass pea genotypes showing good growth under salinity strongly indicated their ability to withdraw Na + and to retranslocate K + during reproductive stages which seems to be highly crucial for superior salt tolerance [61], as explained in saltstressed grass pea [39], beans [62] and barley seedlings [61].…”

NaCl Stress-Induced Reduction in Grwoth, Photosynthesis and Protein in Mustard

“…The reduction in crop production observed in various plant species exposed to salt stress is linked to the decline in photosynthesis (Long & Baker, 1986;Chaves et al, 2009). Reduction in the photosynthetic capability of various plant species by salt stress has been documented in a number of reports (Dubey, 1997;Jamil et al, 2007a;Bayuelo-Jimenez et al, 2012). The inhibition in photosynthesis under saline condition can also be explained by the decline in chlorophyll content (Delfine et al, 1999;Jamil et al, 2007).…”

Some Growth Promoting Essential Mineral Elements Alleviates The Salinity Effect on Nitrate Reductase and Hill Reaction Activities in Cotton (Gossypium hirsutum) cv. “CIM 496”

“…The decrease in crop performance detected in various plant groups exposed to salinity is linked to the decline in photosynthesis. Reduction in the photosynthetic capability of various plant species by salt stress has been documented in a number of reports [21,22,23]. Foliar supply of manganese (Mn) in suitable quantity may result an increase in hill reaction activity and growth rate of cells in barley under saline rhizosphere [24].…”