DISTRIBUTION OF DIURNAL ACID METABOLISM IN THE GENUS ISOETES
DISTRIBUTION OF DIURNAL ACID METABOLISM IN THE GENUS ISOETES
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DOI：
10.1002/j.1537-2197.1982.tb13255.x
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发表时间：
1982-02
影响因子：
3
通讯作者：
J. Keeley
中科院分区：
文献类型：
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作者：
J. Keeley
先前的研究揭示了沉水水生水韭（Isoetaceae）中存在类似景天酸代谢的途径。对这个主要水生属的其他 11 个物种的调查显示，所有物种的可滴定酸度和苹果酸浓度都有昼夜波动。可滴定酸度的日波动幅度从 I. bolanderi 的 119（eq g-1 鲜重）到 I. engelmanni 的 44 不等。尽管这些物种在相似的温室条件下生长，但观察到的昼夜酸波动幅度的物种特异性差异是否具有任何意义是值得怀疑的。这是通过对田间植物与温室种植植物进行单一物种比较得出的结果，表明酸波动幅度的变化几乎与温室中所有物种观察到的一样多。这种变化大部分可能是由于季节差异造成的。底物似乎对酸波动幅度影响很小。由于这项调查涵盖了该属的大部分纬度、海拔、栖息地和形态变异范围，因此昼夜酸代谢很可能在水韭属中很常见。最近的证据表明，水下水生 Isoetes howellii Engelmann（水韭科）具有类似于景天酸代谢 (CAM) 的昼夜酸化/脱酸循环（Keeley，1981a）。晚上，I. howellii 浸入水中的叶子将二氧化碳固定为苹果酸，并且该产物会在一夜之间积累。苹果酸在白天被分解，导致每日的波动
Previous studies have revealed a crassulacean acid metabolism-like pathway in the submerged aquatic Isoetes howellii (Isoetaceae). A survey of 11 other species in this largely aquatic genus showed all had diurnal fluctuations in titratable acidity and malic acid concentration. The magnitude of the diurnal fluctuation in titratable acidity varied from 119 (,eq g-1 fresh weight) for I. bolanderi to 44 for I. engelmanni. Although these species were grown under similar conditions in a greenhouse, it is questionable whether or not any significance can be attached to observed species specific differences in magnitude of diurnal acid fluctuation. This is suggested by a single species comparison of plants in the field with greenhouse grown plants which indicated nearly as much variation in magnitude of acid fluctuations as observed across all species in the greenhouse. Much of this variation may be due to seasonal differences. Substrate appears to have very little effect on magnitude of acid fluctuations. Since this survey covered most of the range of the latitudinal, elevational, habitat, and morphological variation in the genus, it is likely that diurnal acid metabolism will prove to be common in the genus Isoetes. RECENT EVIDENCE has been presented that the submerged aquatic Isoetes howellii Engelmann (Isoetaceae) has a diurnal acidification/deacidification cycle similar to crassulacean acid metabolism (CAM) (Keeley, 1981a). At night, submerged leaves of I. howellii fix CO2 into malic acid and this product accumulates overnight. The malic acid is broken down during the day resulting in a diurnal fluctuation of