PHYSIOLOGICAL STUDIES TO REDUCE THE EFFECT OF SALINITY ON THE GROWTH AND PRODUCTIVITY OF SOME VARIETIES OF LETTUCE PLANT

Abstract

Gamal Shaban Sayed-Ahmed khalifa: Physiological Studies to Reduce the Effect of Salinity on the Growth and Productivity of Some Varieties of Lettuce Plant. Unpublished Ph. D. Thesis, Department of Agricultural Botany, Faculty of Agriculture, Ain Shams University, 2016.

Two field experiments were conducted in the two successive sea-sons of 2012-2013 and 2013-2014 to investigate the effects of salicylic acid (SA) as a growth regulator, glycine betaine (GB) as an osmolyte, se-lenium (Se) and silicon (Si) applications on two lettuce (Lactuca sativa L.) cultivars Great lakes and Balady grown under salt stress (3.22 dSm−1.) in irrigation water. Two levels of SA (200 and 400 ppm), GB (15 and 30 mM), Se (16 and 32 µM) as sodium selenate and Si (1 and 2 mM) as po-tassium silicate were used to adverse the destructive effect of salinity. Application of SA, GB, Se and Si improved growth parameters e.g., plant height, root length, number of leaves per plant, plant fresh weight, plant dry weight, chlorophyll a, b and carotenoids concentration. GB at 30 mM gave the highest significant increase of leaf relative water content (LRWC), accumulation of proline, total soluble sugars (TSS) and total phenols. Treatments also affected the activity of phenylalanine ammonia-lyase (PAL), peroxidase (POD), super oxide dismutase (SOD) and poly-phenol oxidase (PPO) activity and, and K+, Ca++ concentration. However, decreased lipid peroxidation malondialdehyde (MDA), membrane per-meability (MP) and Na concentration.