以2年生枳砧‘砂糖橘’Citrus reticulata ‘Shatangju’幼苗为试材，分别进行正常供镁(对照)和缺镁处理，测定幼苗叶片中镁、叶绿素、蔗糖、淀粉和脱落酸(ABA)等含量及蔗糖磷酸合成酶、酸性转化酶和丙酮酸激酶等活性，以寻找合适的‘砂糖橘’缺镁早期诊断指标。结果表明，与对照相比，缺镁处理112 d 后，植株叶片镁含量显著低于对照，但叶绿素含量未显著降低；蔗糖含量在处理28 d 后出现瞬时增加，但随后恢复至对照水平；ABA 含量在处理56～70 d 时出现显著增加，其他时间没有差异，淀粉含量则与对照一直没有差异；丙酮酸激酶活性对缺镁胁迫没有明显的响应，而蔗糖磷酸合成酶和酸性转化酶在处理14 d 后活性显著下降，且后者几乎在整个采样期维持低水平。因此，初步得出‘砂糖橘’叶片的酸性转化酶活性可作为植株缺镁的即时响应指标，能较快地反映植株是否处于缺镁状态，同时，蔗糖磷酸合成酶、蔗糖和 ABA 含量可作为辅助指标。%In this study, the 2-year-old seedlings of Citrus reticulata ‘Shatangju’ grafted on Poncirus trifoliata were used as experimental materials with two treatments: the magnesium-deficiency treatment and the control. The contents of magnesium, chlorophyll, sucrose, starch, abscisic acid and the activities of sucrose phosphate synthase, acid invertase, pyruvate kinase of ‘Shatangju’ leaves were measured to find some indexes predicting whether the plant be lack of magnesium in advance. The results were as follows: comparing with the control, the content of leaf magnesium was significantly lower at 112 d, but there was no significant difference in cholorophyll; the content of sucrose temporarily increased at 28 d after lacking magnesium, and then restored to the control level. Besides, ABA content significantly increased at 56 d and 70 d, but not at other sampling time. The content of starch in the leaves short of was not significantly different from the control throughout the entire experiment, so was the activity of pyruvate kinase. And the activities of sucrose phosphate synthase and acid invertase declined significantly at 14 d, and the latter responded sensitively to magnesium deficiency all the time. So it was preliminarily concluded that the activity of acid invertase in ‘shatangju’ leaves could be used as an instant response index for magnesium deficiency, meanwhile the activity of sucrose phosphate synthase and contents of sucrose and ABA could be used as supplementary indexes.
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