Potassium deficiency increases specific leaf weights and leaf glucose levels in field-grown cotton

Potassium deficiency reduces Lint yield and causes fiber quality problems f or cotton (Gossypium hirsutum L) producers throughout the U.S, production r egions, This deficiency produces plants exhibiting reduced leaf area but in creased specific leaf weights (SLW). The objectives of this research were ( i) to determine whether the alterations in leaf growth produced by a ii def iciency are associated with changes in leaf carbohydrate levels or leaf wat er status and (ii) to determine if a K deficiency alters the carbohydrate c oncentration in root tissue. Field studies were conducted in 1993 and 1993 using four genotypes ('DES 119','MD 51 ne','Prema', and 'STV' 825') and two levels of Ii fertilization (0 and 112 kg K ha(-1)). Glucose, fructose, suc rose, and starch concentrations were quantified for leaves collected at thr ee different dates in both years, Root carbohydrate concentrations were det ermined once in each growing season. Leaf water potential and its component s were determined once each growing season using thermocouple psychrometers . Glucose was the only carbohydrate whose leaf concentration was consistent ly altered by the ii deficiency; it was increased an average of 84% across all leaf harvest dates. Leaf concentrations of starch, starch, sucrose, and fructose were inconsistent in their response to variation in Il levels, Th e K deficiency increased root tissue concentrations of starch by 82%, gluco se by 14%, and fructose by 27%, averaged across gears. Although leaf eater potential (psi(1)) and leaf osmotic potential (psi(pi)) were unaffected by varying the level of K fertilization, leaf turgor (psi(t)) averaged across both years was increased 17% in leaves from the Ii-deficient plants. The el evated carbohydrate concentrations remaining in source tissue, such as leav es, appear to be part of the overall effect of Ii deficiency in reducing th e amount of photosynthate available for reproductive sinks and thereby prod ucing reductions in tint yield and fiber quality seen in cotton.