Department of Plant Sciences, University of California, Riverside, California 92521.
Plant Physiol. 1979 Jan;63(1):57-60. doi: 10.1104/pp.63.1.57.
Several lines of evidence implicate ammonium as an important factor in the growth and development of cotton (Gossypium hirsutum L.) ovules cultured in vitro. For example, ovules cultured at 28 C require indoleacetic acid (IAA) and either ammonium or gibberellic acid (GA(3)) in the medium for fiber development, whereas ovules cultured at 34 C require only IAA. Because of this effect of ammonium supply, it seemed possible that hormones or increased temperature were also promoting the availability of reduced nitrogen by induction of increased nitrate reductase activity in the ovules. This possibility was tested.In vivo, where ovules received mostly reduced nitrogen and very little nitrate, they did not display appreciable nitrate reductase activity even when nitrate was forced into the ovary wall by transpiration. After initiation of culture, nitrate became freely available to ovules and their nitrate reductase activity increased rapidly. Treatment with ammonium, GA(3), IAA, or increased temperature had no effect upon this induction. It is concluded that ammonium, hormone, and temperature effects on fiber development are independent of the availability of reduced nitrogen as a general substrate for growth.
有几条证据表明，铵是棉花（Gossypium hirsutum L.）胚珠在体外培养中生长和发育的重要因素。例如，在 28°C 下培养的胚珠在培养基中需要吲哚乙酸（IAA）和铵或赤霉素（GA(3)）才能发育出纤维，而在 34°C 下培养的胚珠只需要 IAA。由于铵供应的这种影响，似乎有可能激素或升高的温度也通过诱导胚珠中硝酸还原酶活性的增加来促进还原态氮的可用性。这种可能性通过实验进行了检验。在体内，胚珠接收的主要是还原态氮，很少有硝酸盐，即使通过蒸腾作用将硝酸盐强制进入子房壁，它们也不会表现出明显的硝酸还原酶活性。培养开始后，硝酸盐对胚珠变得自由可用，其硝酸还原酶活性迅速增加。用铵、GA(3)、IAA 或升高的温度处理对这种诱导没有影响。因此，可以得出结论，铵、激素和温度对纤维发育的影响与还原态氮作为生长的一般底物的可用性无关。
