ORIGINAL PAPER Effect of salt stress on cucumber: Na + –K + ratio, osmolyte concentration, phenols and chlorophyll content Jagesh K. Tiwari Æ Anilabh D. Munshi Æ Ravinder Kumar Æ Raghu N. Pandey Æ Ajay Arora Æ Jayant S. Bhat Æ Amish Kumar Sureja Received: 3 December 2008 / Revised: 27 July 2009 / Accepted: 26 August 2009 / Published online: 15 September 2009 Ó Franciszek Go ´rski Institute of Plant Physiology, Polish Academy of Sciences, Krako ´w 2009 Abstract A pot experiment with 17 diverse genotypes of cucumber with four levels of salt stress viz., 0, 2, 4 and 6 dS m -1 was carried out during 2006. ANOVA revealed significant differences amongst genotypes and geno- type 9 salt stress interaction indicating the genetic vari- ability and differential response of the genotypes to different salt stress levels. The salt stress adversely affected the biochemical parameters; effects were severe under 4 dS m -1 . No genotype could survive at 6 dS m -1 . Sodium content, Na ? –K ? ratio, proline, reducing sugars, phenol and yield reduction (%) increased significantly as the salt stress increased. Potassium, chlorophyll, membrane stability index and fruit yield decreased significantly under salt stress in all genotypes. However, the genotypes CRC-8, CHC-2 and G-338 showed lower accumulation of sodium, lesser depletion of potassium, lower Na ? –K ? ratio and higher accumulation of proline, reducing sugars, phenols, better membrane stability and lower yield reduction (%) under salt stress, while CH-20 and DC-1 were sensitive to salt stress. Thus, a combination of traits such as higher membrane stability, lower Na ? –K ? ratio, higher osmotic concentration and selective uptake of useful ions and prevention of over accumulation of toxic ions contribute to salt stress tolerance in cucumber. These traits would be useful selection criteria during salt stress breeding in cucumber. Keywords Cucumber  Salt stress  Na ? –K ? ratio  Chlorophyll  Membrane stability  Osmolyte  Phenol Introduction Salt stress is an important growth-limiting factor for most non-halophytic plants. Unfortunately, high level of salts cannot be tolerated by most crops, a fact that severely limits the use of salt affected soils. Salt affected soil is progressively being exacerbated by agronomic practices such as improper irrigation and fertilisation, especially in arid regions (Villa-Castorena et al. 2003). At higher salt levels, the crop yields are reduced so drastically that crop cultivation is not economical without soil amendments. The addition of salts to water lowers its osmotic potential, resulting in decreased availability of water to roots and thus exposes plants to secondary osmotic stress. This implies that all the physiological responses associated with the drought stress can also be invoked by salt stress. Communicated by A. Aniol. J. K. Tiwari  A. D. Munshi  R. Kumar Division of Vegetable Science, Indian Agricultural Research Institute, Pusa 110 012, New Delhi, India R. N. Pandey Division of Soil Science and Agricultural Chemistry, Indian Agricultural Research Institute, Pusa 110 012, New Delhi, India A. Arora Division of Plant Physiology, Indian Agricultural Research Institute, Pusa 110 012, New Delhi, India J. S. Bhat Department of Genetics and Plant Breeding, Institute of Agriculture, Visva Bharati, Sriniketan, West Bengal, India A. K. Sureja (&) Department of Vegetable Science, College of Horticulture and Forestry, Central Agricultural University, Pasighat 791 102, Arunachal Pradesh, India e-mail: aksureja@rediffmail.com; aksureja@yahoo.co.in 123 Acta Physiol Plant (2010) 32:103–114 DOI 10.1007/s11738-009-0385-1