Abstract
Effect of transient oxygen stress on cotton at various growth stages of cotton was investigated in soil culture under wirehouse conditions during 1981-83. Eighteen days submergence at pre-flowering stage markedly retarded cotton plant growth. Submer-gence for 7days of 15-day old plants was as deleterious as sulitner* genco for 14 days of 35-day old plants indicating that cotton was more Eensitive to oxygen stress at early stages of growth. Longer period (10-days) of sumliergence proved more detrimental to 1-2 weeks old plants than the short submergence period (5 days).
INTRODUCTION
Although Pakistan ranks fifth in the world as far as the cotton acrage is concerned, yet its t'ie'd per unit area is low due to multiple factors; salinity and waterlogging being the most detrimental. Active growth period of cotton coin-cides with the rainy season aril heavy rains often cause temporary flooding in the fields depending upon the watertable and infiltration rate of the soil. Flooding fills the soil pore space with water and gas exchange between soil and atmosphere is virtually eliminated. The rate at which dissolved oxygen in the soil water is depleted depends sensitively on the soil temprature and res. piration rate of roots and microorganisms (Drew, 1983). With warm tempera-tures depletion may be complete in only hours (Trought and Drew, 1980; Troughs and Drew, 1982). At the same time, the ability of cotton roots to survive conti-nuously anaerobic conditions is of short duration, ranging from 0,5-3.0 h (Huck, 1910) and cotton growth is adversely aff5uted. by lack of oxygen. In this paper we report the response of cotton to transient oxygen stress at different stages of growth eye]e.
BIT FRIARS AND METHODS
The methodology used in various experiments is briefly described below. Experiment I Cotton variety B-657 was grown in pots containing 10kg normal sandy clay
*Deptt. of Soil Science, University of Agriculture, Faisalabad,
