Abstract
A hydroponics experiment was conducted to evaluate the role of potassium （K） and silicon （Si） in mitigating the deleterious effects of NaCl on sugarcane genotypes differing in salt tolerance. Two salt-sensitive （CPF 243 and SPF 213） and two salt-tolerant （HSF 240 and CP 77-400） sugarcane genotypes were grown for six weeks in 1/2 strength Johnson＇s nutrient solution. The nutrient solution was salinized by two NaCl levels （0 and 100 mmol L^-1 NaCl） and supplied with two levels of K （0 and 3 mmol L^-1） and Si （0 and 2 mmol L^-1）. Applied NaCl enhanced Na^＋ concentration in plant tissues and significantly （P 〈 0.05） reduced shoot and root dry matter in four sugarcane genotypes. However, the magnitude of reduction was much greater in salt-sensitive genotypes than salt-tolerant genotypes. The salts interfered with the absorption of K^＋ and Ca^2＋ and significantly （P ≤0.05） decreased their uptake in sugarcane genotypes. Addition of K and Si either alone or in combination significantly （P ≤0.05） inhibited the uptake and transport of Na^＋ from roots to shoots and improved dry matter yields under NaCl conditions. Potassium uptake, K^＋/Na^＋ ratios, and Ca^2＋ and Si uptake were also significantly （P ≤ 0.05） increased by the addition of K and/or Si to the root medium. In this study, K and Si-enhanced salt tolerance in sugarcane genotypes was ascribed to decreased Na^＋ concentration and increased K^＋ with a resultant improvement in K^＋/Na^＋ ratio, which is a good indicator to assess plant tolerance to salt stress. However, further verification of these results is warranted under field conditions.