2,4—D对甜橙幼果脱落及离区纤维素酶活性的抑制效应

暗柳橙(Citrus sinensis Osbeck)第一次生理落果期(3月下旬～4月中旬)的果实外植体脱落过程中,离区纤维素酶A、B的活性明显升高,第二次落果(4月下旬～5月中旬)期的果实脱落过程中,纤维素酶A的活性也显著提高,但纤维素酶B活性变化较小。细胞内、外纤维素酶的活性在外植体脱落过程中也不断升高。2,4—D能明显抑制胞内、外纤维素酶及纤维素酶A的活性,同时还能抑制外植体及非离休果实内乙烯的产生,但对纤维素酶B活性的影响无明显效应。田间喷布低浓度的2,4—D,明显地减少第一次生理落果,但对第二次落果的作用不如赤霉素。本文还讨论了果实的脱落、纤维素酶活性与乙烯之间的相互关系,及2,4—D的调控作用。并认为采用外植体的方法不失为研究脱落问题的有效手段。

THE SUPPRESSIVE EFFECTS OF 2,4-D ON PREMATURE DROP OF ORANGE AND CELLULASE ACTIVITY IN THE ABSCISSION ZONE

The cellulase A(buffer-soluble)and B(salt-soluble)activities in abseission zone of fruit explants of "Anliu-cheng" orange(Citrus sinensis Osbeck)rose markedly during prenalure drop just after petal fall(first fruit drop),cellulase A activity in the abscission layers of fruit explant and attached fruit also increased significantly in the course of the shedding at the disc(second fruit drop),but there was little change in rellulase B during that time.2,4-D could inhibit not only the abscission of fruit explants collected in the two fruit drops just mentioned above,but also first fruit drop in the field by low concentration spraying,due to the marked depression of the exo-and endo cellular cellulase,cellulase A activity and ethylene production.But it had no significant effect on cellulase B activity in this experiment.The use of gibberellic acid in decreasing fruit shedding during the second drop was more effective than that of 2,4-D.The relationships among fruit abscission,cellulaseactivity and ethylene production and the regulating mechanism of 2,4-D on fruit drop were discussed.