THE INFLUENCE OF SALINITY AND DROUGHT STRESS ON SODIUM,

POTASSIUM AND PROLINE CONTENT OF

SOLANUM LYCOPERSICUM L. cv. RIO GRANDE

 

SYED GHIAS ALI^1* AND ABDUR RAB²

 

¹Centre of Plant Biodiversity, University of Peshawar, Pakistan

²Department of Horticulture, The University of Agriculture, Peshawar, Pakistan

^*Corresponding author e-mail: ghiasghias06@hotmail.com

Abstract

The influence of salinity and drought stress on sodium (Na⁺), potassium (K⁺) and proline content of Solanum lycopersicum L. (tomato) cv. Rio Grande was investigated by exposing the plants to five salinity levels i.e., 0 (control), 50, 100, 150 and 200 mM NaCl and four drought regimes i.e. 0 (Control), 2, 4 and 6 days, applied from seedling (4-5 true leaves) to the harvesting stage. The means across salinity levels showed an increase in proline content and Na⁺ concentration but a  reduced K⁺ concentrations, resulting in high Na⁺/K⁺ ratios in shoot and root tissue. In contrast, drought stress decreased the Na⁺ and K⁺ content, Na⁺/K⁺ ratio but increased the proline content in both the root and shoot tissue. The interaction of salinity and drought significantly affected the sodium (Na⁺) and potassium (K⁺) contents, Na⁺/K⁺ and proline content of the shoot but K⁺  content and proline accumulation were not significant. The root and shoot tissue of control plants (0 mMNaCl + 0 Days drought stress) had the minimum Na⁺ content (2316 and 3490 µM/g D.wt.), Na⁺/ K⁺ ratio (0.399 and 0.364) and proline content (0.72 and 1.91 µM/g F.wt.) but the highest K⁺ content (6399 and 9603 µM/g D.wt.). Whereas, the Na⁺ content increased with salinity, the K⁺ content declined. It resulted in the maximum Na⁺/K⁺ ratio of the root (1.26) and shoot (0.76) with 200 mMNaCl + 0 Days drought stress. The drought stress also increased the Na⁺/K⁺ ratio. Thus, the highest Na⁺/K⁺ ratio of root (0.78) and shoot (0.77) was recorded in plants grown under 200 mMNaCl+ 6 Days drought stress. The proline content of the root and shoot were 0.462 and 1.904 µM/g F.wt. respectively in control plants which increased with increasing salinity and drought stress duration. Thus, the maximum proline content of root (10.61 µM/g F.wt.) and shoot (28.05 µM/g F.wt.) was recorded in plants exposed to 200 mMNaCl + 6 days drought stress combination.

 

Key words: Tomato, Salinity, Drought, Proline, Na⁺ and K⁺