Wang Zhaolong, Mambelli Stefania, Setter Tim L
Department of Crop and Soil Sciences, Cornell University, Ithaca, NY 14853, USA.
Ann Bot. 2002 Nov;90(5):623-30. doi: 10.1093/aob/mcf239.
To further our understanding of the greater susceptibility of apical kernels in maize inflorescences to water stress, abscisic acid (ABA) catabolism activity was evaluated in developing kernels with chirally separated (+)-[(3)H]ABA. The predominant pathway of ABA catabolism was via 8'-hydroxylase to form phaseic acid, while conjugation to glucose was minor. In response to water deficit imposed on whole plants during kernel development, ABA accumulated to higher concentrations in apical than basal kernels, while both returned to control levels after rewatering. ABA catabolism activity per gram fresh weight increased about three-fold in response to water stress, but was about the same in apical and basal kernels on a fresh weight basis. ABA catabolism activity was three to four-fold higher in placenta than endosperm, and activity was higher in apical than basal kernels. In vitro incubation tests indicated that glucose did not affect ABA catabolism. We conclude that placenta tissue plays an important role in ABA catabolism, and together with ABA influx and compartmentation, determine the rate of ABA transport into endosperms.
为了进一步了解玉米花序中顶端籽粒对水分胁迫更敏感的原因，我们使用手性分离的(+)-[(3)H]脱落酸(ABA)评估了发育中籽粒的ABA分解代谢活性。ABA分解代谢的主要途径是通过8'-羟化酶形成 phaseic 酸，而与葡萄糖结合的途径则较少。在籽粒发育过程中对整株植物施加水分亏缺时，顶端籽粒中ABA积累的浓度高于基部籽粒，而复水后两者均恢复到对照水平。每克鲜重的ABA分解代谢活性因水分胁迫而增加约三倍，但以鲜重计，顶端和基部籽粒中的活性大致相同。胎座中的ABA分解代谢活性比胚乳高3至4倍，且顶端籽粒中的活性高于基部籽粒。体外孵育试验表明，葡萄糖不影响ABA分解代谢。我们得出结论，胎座组织在ABA分解代谢中起重要作用，并且与ABA流入和区室化一起，决定了ABA向胚乳的转运速率。
