Diurnal water relations of expanding and full‐sized cotton fruits and subtending leaves

Abstract

ABSTRACTWater relations of cotton (Gossypium hirsutum L.) fruits have received less attention than those of leaves, although crop water status has an important influence on fruit physiology. This study was conducted to describe diurnal changes in the water relations of cotton fruits and subtending leaves. Young, expanding fruits and full‐sized fruits were compared because of previously reported changes in xylem maturity with ontogeny. Diurnal changes in relative water content were greater in leaves than in the capsule walls of fruits. The capsule walls of young fruits had a higher relative water content than subtending leaves, and water content was lower in full‐sized (87%) than in expanding (92%) fruits. Water potentials of subtending leaves were always approximately 0‐3 MPa lower than those of capsule walls. Water potential gradients favoured passive water flow from young fruits to branches, but water potentials of branches and the capsule walls of full‐sized fruits were similar (−0.7 MPa). Water potential gradients were consistent throughout the day. These results indicate that xylem transport to young fruits is unlikely, but may occur in older fruits.