Influence of extreme K:Na ratios and high substrate salinity on plant metabolism of crops differing in salt tolerance.VII. Relations between carbohydrates and degradative enzymes in salt tolerant and salt sensitive cotton genotypes during initial salinity stress

Abstract

The effects of salinity on carbohydrates in leaves and roots of different salt tolerant cotton genotypes Glza 45 (salt tolerant) and Dandara (salt sensitive) during the initial salinity stress are investigated. Changes of starch and sucrose in relation to soluble amylases, phosphorylase and invertase in young leaves are studied. The plants are grown in water culture under controlled conditions.

Starch and sucrose accumulation is rapidly stimulated in leaves of Dandara, particularly due to extreme potassium sulfate supply, while in Giza 45 the amount of starch and sucrose declines except for extreme potassium sulfate treatment. The low sucrose value in roots of Dandara increases extremely, especially as a result of potassium chloride treatment. In contrast, the higher sucrose content in roots of Giza 45 is little affected. Amylase activity changes considerably in positive correlation with the starch content, whereas the low specific activity of phosphorylase is little affected. The sucrose content in the leaves is directly controlled by a high level of invertase activity of both cotton varieties.

Possible interactions of carbohydrate metabolism and genotyplcal ion regulation in response to the different salt tolerance of the genotypes are discussed. It is concluded that genotypical differences in the carbohydrate metabolism could be effective mechanisms for salt tolerance in cotton.

Key words:

• Carbohydrates
• amylases
• phosphorylase
• invertase
• Gossypium barbadense genotypes
• salt tolerance