عنوان مقاله [English]
Salinity has various effects on plant growth by affecting physiological processes. The decline in plant productivity under saline condition, frequently linked with the reduction of photosynthetic capability. It has been reported that efficiency of PSII photochemistry (Fv/Fm) of numerous plant species have been decreased due to salt stress studies have shown that salicylic acid (SA( improves resistance of plants to environmental stresses (heat, cold, drought and salt stress). In this relation, convincing data have showed that the SA-induced enhances resistance of plants to the salinity. Therefore, the present study was conducted to estimate salicylic acid effects on germination, growth and some physiological characteristics of two chickpea genotypes (Cicer arietinum L.) in salt stress condition.
Materials and Methods
In this research we studied the effects of different concentrations of SA (0.5 and 1mM), on chickpea genotypes (MCC414, MCC789) during growth stages (germination, seedling and flowering) under salinity stress. Five levels of salinity including 0, 3, 5, 10 and 12 dsm-1 in germination stage and three levels of salinity (0, 4 and 8 dsm-1) at seedling and flowering stages) were employed separately in a factorial experiment based on Randomized Completely Block Design with three replications.
Results and Discussion
Results of means comparison showed that germination rate, significantly decreased under salt stress in both genotypes (P≤0.05). Under salt stress, increasing the osmotic pressure and the reduction seeds water absorption and the toxic effects of sodium and chlorine ions, can affect seed germination. Exogenouse application of SA concentrations (0.5 mM), under salt stress (3 and 12 dsm-1) increased rate and percentage of germination in MCC789 genotype. For MCC414 genotype, the combination of the treatment with salicylic acid (0.5 and 1 mM) and salinity (10 dsm-1) increased significantly germination rate. In same genotype, radicle and coleoptile length increased significantly after treating with SA (1mM) in salt stress (12 dsm-1). Exogenous application of SA concentration (0.5 mM), under salt stress (3 dsm-1) increased coleoptile length in MCC789 genotype (P≤0.05). Seed priming with SA leads to an activation of germination and seedling growth, while the enhancement of the division of root apical cells are important contribution to the growth stimulating effect of SA. In seedling stage, salinity decreased stem and root dry weight. SA and on some salinity levels, significantly increased stem dry weight in MCC789 and total root length in MCC414 genotype (P≤0.05). The decline in plant productivity under saline condition is frequently linked with the reduction in leaf area and stomatal conductance. Positive effects of SA on growth characteristics, in wheat, barley and maize have been reported. In both genotype, chlorophyll index, transpiration rate, membrane stability index and efficiency of PSII photochemistry significantly decreased and stomatal resistance increased under salt stress in flowering stage. Serious reduction in stomatal conductance and transpiration rate are adaptive mechanisms under salt stress. Halophytes such as Beta vulgaris and Spartina townsendi have salinity tolerance and show a combination of low photosynthesis, minimal transpiration, high stomatal resistance and low internal CO2 concentrations. Studies showed chlorophyll contents decreased under saline condition. Biochemical analysis of leaves of different maize cultivars for proline and chlorophyll contents indicated that proline accumulation increased and chlorophyll contents decreased under saline condition. SA application increased chlorophyll index and membrane stability index respectively in MCC789 and MCC414 genotypes. In both genotypes, stomatal resistance, significantly decreased and efficiency of PSII photochemistry increased with SA treatment under salt stress (12 dsm-1) (P≤0.05). Studies have shown that salicylic acid protects membranes by increasing polyamines such as putrescine, spermine, spermidine, as well as membrane sustainable complexes. In wheat, SA application improves the Fv/Fm. Szepesi et al, (2005) reported SA (10-6 and 10-7 M) could increase Fv/Fm in tomato plants under drought stress.
The results indicated that the modulator effects on salicylic acid on germination and other physiological processes of chickpea genotypes under salt stress.
Key words: Chickpea (Cicer arietinum L.), Efficiency of PSII photochemistry, Growth parameters, Membrane stability index, Salicylic acid, Salt stress