Selecting Rice Genotypes Tolerant to Zinc Deficiency and Sodicity: Differences in Concentration of Major Cations and Sodium/Potassium Ratio in Leaves

Abstract

Zinc (Zn) deficiency is a major nutritional problem for rice under sodic conditions. Seedlings (35-d old) of 30 rice genotypes were transplanted in pots at pH 2 9.8 [diethylene triamine penta acetic acid (DTPA) Zn 1.8 ppm] to identify genotypes tolerant to both sodicity and Zn deficiency. Ten genotypes (group A) showed potential to tolerate both the stresses. Sixteen genotypes (group B) were sensitive to Zn deficiency. However, some of the seedlings of group B genotypes were normal (without Zn deficiency symptoms). Four genotypes (group C) were sensitive to sodicity. Leaves and their leaf sheaths were analyzed at 33 d after transplanting for Ca, Mg, K, and Na. Group A genotypes (CSR-88IR15, CSR-89IR14, IR4630-22-2-5-1-2, and Trichi) had significantly less Na concentrations in their leaves and the leaf sheaths compared to group B genotypes (CSR10, CSR23, CSR-88IR1, 89H1-931098, and IR47538-3B-9-3B-1). The concentration of Na was invariably higher in the leaf sheath than its leaf in both the groups, but reverse was true for Ca, Mg, and K. Zinc deficient plants had relatively higher concentrations of Ca and Mg in their leaves and the leaf sheaths than group A. Concentration of K was somewhat better in group A than group B genotypes. Higher Na/K ratio in group B genotypes compared to group A may be attributed to increased concentrations of Na rather than decreases in K concentrations. Further studies are needed to understand the processes associated with differential uptake of Na and K by Zn deficient plants of group B genotypes resulting in higher Na/K ratio compared to group A genotypes.

Potassium-induced alleviation of salinity stress in Brassica campestris L.

“…K nutrition ameliorated to a great extent the Na + and Cl --accrued decrease in reducing equivalents viz., AsA and GSH which, in turn, had a tight control over the balance between production and scavenging of H 2 O 2 and stabilized the cell membrane by decreasing TBARS content through coordination with other components of the AsA-GSH cycle. Our findings that K nutrition improves the leaf K + and decreases the Na + and Cl -contents confirm those of Qadar and Azam [10], Zheng et al [40,45] and More and Manchanda [39].…”

“…In this context, we have shown that the addition of K to the NaCl-treated plants proved to be effective in protecting B. campestris plants against NaCl-caused oxidative stress by decreasing Na + and Cl -content and increasing K + in leaves. The antagonistic effect of K + and Na + on uptake of each other is well documented and reported in both saline and sodic conditions [10,27,39,40]. Added K also improved AsA and GSH contents, and further enhanced the activity of APX and GR, whereas the activity of SOD dropped with K-supplementation to the NaCl-treated plants.…”

“…A level of nutrients considered being sufficient for plant growth under non-stress conditions may or may not be sufficient under salt stress. Where plant growth is also adversely affected because of higher nutrient requirement under salt stress, increased supply of nutrients is likely to benefit plants under stress [9,10]. Grattan and Grieve [11] have extensively reviewed the impact of increased nutrient supply on horticultural crops under salt stress.…”