CAUSES OF GROWTH REDUCTION IN ELONGATING AND EXPANDING LEAF TISSUE OFSUGARCANE UNDER SALINE CONDITIONS

Plants of sugarcane, cv. Co 1148, were subjected to salinisation with 200 milliequivalents L(-1) of Cl--type salts mixture (having Na+, Ca2 and Mg2+ as 3:1:1 and Cl- and SO42- as 4:1 on a milliequivalent basis ) for two weeks or more during the tillering phase. Soluble sugar conc entrations increased by 55% in the blades of recently matured leaves ( source tissues) and by nearly 225% in the elongating sheath bases (sin k tissues) as a result of salinisation. Leaf elongation within 3 h of desalinisation was much faster than for the non-saline controls. The a ccumulated sugars also dropped in the rapidly elongating sheath bases by 43% during this period after desalinisation. Further, the drop in s ugar levels upon desalinisation was of greater magnitude in the more r apidly growing sheath bases. The present studies indicate that even th ough the supply of carbohydrates from the source tissues is reduced, t he sink tissues are not able to make use of these sugars under saline conditions. As Na+ and Cl- concentrations did not change within 3 h of desalinisation, the ions themselves did not appear to affect metaboli c activities of the sink tissues; this suggestion is further supported by the utilisation of accumulated sugars within 3 h of desalinisation .