Ramaih Shashi, Guedira Mohammed, Paulsen Gary M
Department of Agronomy, Throckmorton Hall, Kansas State University, Manhattan, KS 66506-5501, USA.
Department of Agronomy, Throckmorton Hall, Kansas State University, Manhattan, KS 66506-5501, USA. Corresponding author; email:
Funct Plant Biol. 2003 Oct;30(9):939-945. doi: 10.1071/FP03113.
Preharvest sprouting of wheat (Triticum aestivum L.) involves several plant hormones, but a role for indoleacetic acid (IAA) and its precursor, tryptophan, has not been demonstrated. Our objectives were to determine the roles of IAA, tryptophan, and related compounds in germination of cultivars that differed in susceptibility to preharvest sprouting. L-Tryptophan strongly inhibited germination of embryos excised from caryopses that were highly dormant at harvest but not of embryos from caryopses that had little innate dormancy. The embryos responded similarly to indoleacetaldehyde, IAA, and synthetic auxins, suggesting that tryptophan functioned as a precursor of IAA. Indoleacetaldehyde oxidase inhibitors alleviated the adverse effects of tryptophan and indoleacetaldehyde, and an auxin antagonist decreased the inhibitory action of tryptophan and IAA on embryos from dormant caryopses, further suggesting that IAA was involved. Changes in sensitivity to IAA during afterripening also supported a role for auxin in dormancy. Embryos from caryopses that were highly dormant at harvest gradually lost sensitivity to IAA during afterripening, whereas intact caryopses were insensitive to IAA. The results implicated IAA in dormancy of wheat caryopses and indicated that the auxin might complement the role of abscisic acid in germination. The importance of using dormant caryopses and arresting afterripening in investigations of seed dormancy was noted.
小麦（Triticum aestivum L.）的收获前发芽涉及多种植物激素，但吲哚乙酸（IAA）及其前体色氨酸的作用尚未得到证实。我们的目标是确定IAA、色氨酸及相关化合物在对收获前发芽敏感性不同的品种萌发中的作用。L-色氨酸强烈抑制从收获时高度休眠的颖果中切下的胚的萌发，但对天生休眠较少的颖果中的胚没有抑制作用。胚对吲哚乙醛、IAA和合成生长素的反应相似，表明色氨酸作为IAA的前体发挥作用。吲哚乙醛氧化酶抑制剂减轻了色氨酸和吲哚乙醛的不利影响，生长素拮抗剂降低了色氨酸和IAA对休眠颖果中胚的抑制作用，进一步表明IAA参与其中。后熟过程中对IAA敏感性的变化也支持生长素在休眠中的作用。收获时高度休眠的颖果中的胚在经过后熟后逐渐失去对IAA的敏感性，而完整颖果对IAA不敏感。结果表明IAA与小麦颖果的休眠有关，并表明生长素可能补充脱落酸在萌发中的作用。文中指出了在种子休眠研究中使用休眠颖果和阻止后熟的重要性。
