ABSTRACT
The components of water potential of a developing sympodial branch, and the effect of a mild water-deficit on the organs at the first fruiting position were investigated on field-grown cotton (Gossypium hirsutum L) cv. Stoneville 506. All measurements were made with thermocouple psychrometers. At day 37 after initiation of the sympodial branch, the water potential of the leaf, bract and capsule wall at the first fruiting position were -0.83, -0.74 and -0.37 MPa, respectively. These values were similar for the second fruiting position and characteristic for the whole season. A mild water-stress was started one week after anthesis at the first fruiting point of the tenth node. The leaves and bracts of waterstressed plants had lower water and osmotic potentials than the control, while the components of water potential of the capsule wall were unaffected. Since there is no water-potential gradient towards the capsule wall, and the capsule wall shows no reaction to a mild waterstress, it is suggested that the water transport to the boll is an active process, most likely occurring through the phloem. This explanation is being investigated in ongoing research.
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