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Abscission Processes in Cotton: Induction by Plant Water Deficit¹

Premature boll shedding is characteristic of the cotton (Gossypium hirsutum L.) growth habit, but the extent of this shedding is quite variable. This study was undertaken to evaluate the effects of water stress on boll and leaf abscission. The experiments were conducted in a greenhouse using plants grown in pots containing sand. Plant water deficits were induced by withholding water. Leaf water potentials measured with a pressure bomb were used to quantify the plant water deficit.

The extent of both boll and leaf abscission increased in a linear manner as leaf water potentials decreased from –10 to –24 bars. Abscission induced by water stress was dependent upon age of the tissue. Older leaves were shed as a result of relatively mild water deficits, while juvenile leaves did not abscise even after severe water deficits. Young, immature bolls were most sensitive to water stress. Bolls that remained on the plant approximately 14 days were retained by the plant even after exposure to a severe plant water deficit. A predawn leaf water potential of about –8 bars was required to induce significant leaf abscission.

Key Words: Leaf water potential • Leaf abscission • Boll abscission

² Present address: U.S. Delta States Agricultural Research Center, Cotton Physiology Research Laboratory, Box 225, Stoneville, Miss. 38776.

³ Research Assistant, Assistant Professor, and Associate Professor, respectively, Department of Plant Sciences, Texas A&M University, College Station, Texas 77843.

Received for publication February 5, 1972.