Widmann K, Gebauer G, Rehder H, Ziegler H
Institut für Botanik und Mikrobiologie der Technischen, Universität München, Arcisstrasse 21, W-8000, München 2, Germany.
Lehrstuhl für Pflanzenökologie der Universität Bayreuth, Universitätsstrasse 30, W-8580, Bayreuth, Germany.
Oecologia. 1993 May;94(1):146-152. doi: 10.1007/BF00317316.
The CAM (Crassulacean acid metabolism) succulent species Kalanchoe daigremontiana, K. tubiflora and Crassula argentea, and the succulent C species Peperomia obtusifolia, were cultivated in pure culture in open-air conditions under two different regimes of nitrogen and water supply. At specified intervals during the course of vegetative growth, biomass, nitrate reductase activity (NRA), nitrate concentration, and organic nitrogen concentration of whole plants were measured. After 100 days of cultivation the leaf conductance of Crassula and Peperomia was measured at intervals for the duration of a day. Behaviour of all four species was strongly influenced by the cultivation regime. This was apparent in terms of productivity and variable flucturations in NRA, nitrate concentration, and organic nitrogen concentration during the vegetative period. Increase in biomass was mostly connected with a decrease in all other investigated parameters, especially under conditions of water and/or nitrogen deficiency. The typical reaction of the CAM species Crassula to limited netrogen but adequate soil water was to reduce leaf conductance during light, whereas the C plant Peperomia increased conductance in comparison with plants having a nitrogen suppy. The NRA of all plant species was reduced by both soil nitrate deficiency and drought. The succulent plant species, which are specially adapted to drought, neither took up nor used nitrate when water was limited. This was particularly the case for the CAM species, but less so for the C Peperomia, which showed very high concentrations of nitrate and organic nitrogen, but low NRA and biomass gain. A formula was derived to express the nitrogen use efficiency (NUE) of the species, i.e. the ability of a plant to use nitrogen over a specific period of growth. NUE was shown to increase with age for the crassulacean species but to decrease for the C Peperomia. Furthermore, NUE varied with the different nutrient levels in a species-specific manner, with high values for NUE not necessarily coupled to high productivity, and with NUE of the C species generally higher than that of CAM species.
景天酸代谢（CAM）肉质植物大叶落地生根、管花伽蓝菜和玉树，以及C类肉质植物钝叶椒草，在露天条件下的纯培养中，在两种不同的氮和水供应方案下进行栽培。在营养生长过程中的特定间隔时间，测量整株植物的生物量、硝酸还原酶活性（NRA）、硝酸盐浓度和有机氮浓度。栽培100天后，在一天的时间段内间隔测量玉树和椒草的叶片导度。所有四个物种的行为都受到栽培方案的强烈影响。这在生产力以及营养期内NRA、硝酸盐浓度和有机氮浓度的可变波动方面表现明显。生物量的增加大多与所有其他研究参数的降低相关，特别是在水和/或氮缺乏的条件下。CAM物种玉树对有限氮但充足土壤水分的典型反应是在光照期间降低叶片导度，而C植物椒草与有氮供应的植物相比增加了导度。所有植物物种的NRA都因土壤硝酸盐缺乏和干旱而降低。特别适应干旱的肉质植物物种在水分有限时既不吸收也不利用硝酸盐。CAM物种尤其如此，但C类椒草情况稍好，其硝酸盐和有机氮浓度非常高，但NRA和生物量增加较低。推导了一个公式来表示物种的氮利用效率（NUE），即植物在特定生长时期利用氮的能力。结果表明，景天科物种的NUE随年龄增加，而C类椒草的NUE则降低。此外，NUE以物种特异性方式随不同营养水平而变化，NUE值高不一定与高生产力相关，且C类物种的NUE通常高于CAM物种。
