Water relations of cotton (Gossypium hirsutum L.) fruiting points of three cultivars of different maturity were investigated. The cultivars used in this study were Tamcot HQ 95 (early maturing), Stoneville 506 (mid-early), and LA887 (late). Transpiration and diffusive resistance of the sympodial leaf were measured with a steady state porometer, components of water potential of the leaf, bracts, and capsule wall were measured with end-window thermocouple psychrometers, and hydraulic conductivity of the branch, petiole,and peduncle of Stoneville 506 were measured with a Scholander type pressure chamber at a pressure of 0.2 MPa. All measurements were made at the first fruiting position of main-stem node 10 and a mild water-deficit stress was started at anthesis.

the transpiration and diffusive resistance of the sympodial leaves were not influenced by the different water-regimes, but did change significantly over time. The diffusive resistance increased and the transpiration of all three cultivars decreased during leaf development. This may have been related to a decrease in hydraulic conductivity of the petiole and peduncle during development. The diffusive resistance of LA 887 was higher than those of Stoneville 506 and Tamcot HQ 95, while the transpiration of LA 887 was lower. The lower transpiration of LA 887 was probably caused by a lower leaf turgor potential in LA 887 than in the other two cultivars.

The components of water potential of the capsule wall of the three cultivars were not significantly different. The different water-regimes did not have any influence on the components of water potential of the capsule wall from 0 till 30 days after anthesis, but did have a strong effect in the period from 30 till 50 days after anthesis. During this period, the water and turgor potential of the capsule wall in the stressed plots were approximately 0.3 MPa lower than in the well-watered plots. this was probably related to fruit opening, which normally occurs around 50 days after anthesis.

Overall it can be concluded from this preliminary report that the water relations of individual fruiting points of the tree cultivars differed and that the developmental stage of the various organs had an important influence on their moisture characteristics.