Davenport T L, Morgan P W, Jordan W R
Department of Plant Sciences, Texas Agricultural Experiment Station, Texas A&M University, College Station, Texas 77843.
Plant Physiol. 1977 Apr;59(4):554-7. doi: 10.1104/pp.59.4.554.
Plant water deficits reduced the basipetal transport of auxin in cotyledonary petiole sections taken from cotton (Gossypium hirsutum L.) seedings. A pulse-labeling technique was employed to eliminate complications of uptake or exit of (14)C-indoleacetic acid from the tissue. The transport capacity or the relative amount of radioactivity in a 30-minute pulse which was basipetally translocated was approximately 30% per hour in petioles excised from well watered seedlings (plant water potentials of approximately -4 to -8 bars). No cotyledonary leaf abscission took place in well watered seedlings. Plant water potentials from -8 to -12 bars reduced the transport capacity from 30 to 15% per hour, and although the leaves were wilted, cotyledonary abscission did not increase appreciably at these levels of stress. The threshold water potential sufficient to induce leaf abscission was approximately -13 bars and abscission increased with increasing stress while the auxin transport capacity of the petioles remained relatively constant (15% per hour). The basipetal transport capacity of well watered petioles tested under anaerobic conditions and acropetal transport tested under all conditions were typically less than basipetal transport under the most severe stress conditions. Cotyledonary abscission took place during and 24 hours after relief of stress with little or no abscission taking place 48 hours after relief of stress. Although the water potential returned to -4 bars within hours after rewatering the stressed plants, partial recovery of the basipetal transport capacity of the petioles was not apparent until 48 hours after rewatering, and at least 72 hours was required to return the transport capacity to near normal values. These data support the view that decreased levels of auxin reaching the abscission zone from the leaf blade influence the abscission process and further suggest that the length of time that the auxin supply is maximally reduced is more critical than the degree of reduction.
植物水分亏缺降低了取自棉花（陆地棉）幼苗子叶叶柄切段中生长素的向基运输。采用脉冲标记技术以消除（14）C - 吲哚乙酸在组织中的吸收或排出的复杂情况。在从充分浇水的幼苗（植物水势约为 - 4至 - 8巴）切下的叶柄中，30分钟脉冲中向基转运的放射性的运输能力或相对量约为每小时30%。充分浇水的幼苗中未发生子叶叶片脱落。- 8至 - 12巴的植物水势使运输能力从每小时30%降至15%，并且尽管叶片萎蔫，但在这些胁迫水平下子叶脱落并未明显增加。足以诱导叶片脱落的阈值水势约为 - 13巴，脱落随着胁迫增加而增加，而叶柄的生长素运输能力保持相对恒定（每小时15%）。在厌氧条件下测试的充分浇水叶柄的向基运输能力以及在所有条件下测试的向顶运输能力通常低于最严重胁迫条件下的向基运输能力。在胁迫解除期间及解除后24小时内发生子叶脱落，胁迫解除后48小时几乎没有脱落发生。尽管在给受胁迫植物重新浇水后数小时内水势恢复到 - 4巴，但叶柄向基运输能力的部分恢复直到重新浇水后48小时才明显，并且至少需要72小时才能使运输能力恢复到接近正常值。这些数据支持这样的观点，即从叶片到达脱落区的生长素水平降低影响脱落过程，并进一步表明生长素供应最大程度减少的时间长度比减少程度更关键。
