Griffiths H, Smith J A C, Lüttge U, Popp M, Cram W J, Diaz M, Lee H S J, Medina E, SCHäfer C, Stimmel K-H
Department of Biology, The University, Newcastle upon Tyne, NE1 7RU, UK.
Department of Botany, University of Edinburgh, Edinburgh, EH9 3JH, UK.
New Phytol. 1989 Feb;111(2):273-282. doi: 10.1111/j.1469-8137.1989.tb00691.x.
A comparison of the performance of two epiphytes with crassulacean acid metabolism (CAM) was made during the rainy season and dry season at the Ciénega el Ostional, Chichiriviche in northern Venezuela. The epiphytic bromeliad, Tillandsia flexuosa has water-retaining tanks and leaf trichomes, and propagates mainly vegetatively to produce large populations in the shrubby island vegetation. The epiphytic orchid, Schomburgkia humboldtiana formed smaller populations, and had large succulent leaves with uniform chlorenchyma and no distinct water-storage parenchyma, unlike T. flexuosa. Both epiphytes were myrmecophilous. Leaf succulence (kg m ) declined by ∼ 10% in the dry season for both plants. Both epiphytes showed reduced CO uptake during Phase I (dark period) and (dawn-dusk) titratable acidity (ΔH ) in the dry season. Water-use efficiency (WUE) was higher for S. humboldtiana (16.0 × 10 mol CO per mol H O compared with 5.0 × 10 for T. flexuosa) although WUE remained constant during rainy and dry season for each species. Sixty to seventy per cent of the dawn dusk titratable acidity was derived internally from respiratory CO (recycling) for both species, and in absolute terms, recycling decreased in the dry season, in contrast to the expected progression under drought stress. Recycling is an important facet of carbon balance for both species in both rainy and dry seasons. Leaf Na concentration was higher than values quoted for terrestrial salt stressed CAM plants. Fructose and glucose declined in leaf bases of T. flexuosa during the dark period, but not in the more distal regions of the leaf. S. humboldtiana showed a decrease in sucrose at night, and mannitol was also an important constituent of the leaves. Xylem sap tension maxima increased from 0.38 ± 0.09 MPa (rainy season) to only 0.55 ± 0.06 MPa (dry season) for T. flexuosa, these values being much lower than those found for terrestrial shrubs and herbs at the same site, the two epiphytes use CAM in conjunction with differing morphological adaptations to maintain growth throughout the year at the Ciénega el Ostional, but it would seem that T. flexuosa has better physiological characteristics for maintenance of carbon acquisition during the dry season.
在委内瑞拉北部奇奇里维切的西耶内加·埃尔·奥西昂纳尔，于雨季和旱季对两种具有景天酸代谢（CAM）的附生植物的性能进行了比较。附生凤梨科植物弯叶铁兰有储水槽和叶毛状体，主要通过无性繁殖形成大量种群，生长在灌木丛生的岛屿植被中。附生兰花洪堡氏堇花兰形成的种群较小，其叶片肉质且大，叶肉组织均匀，没有明显的储水薄壁组织，这与弯叶铁兰不同。两种附生植物均为蚁栖植物。两种植物在旱季时叶片肉质（kg/m）均下降了约10%。在旱季，两种附生植物在第一阶段（黑暗期）的CO吸收量以及黎明 - 黄昏可滴定酸度（ΔH）均降低。洪堡氏堇花兰的水分利用效率（WUE）更高（每摩尔H₂O对应16.0×10⁻⁶摩尔CO₂，而弯叶铁兰为5.0×10⁻⁶），尽管每种植物在雨季和旱季的WUE保持恒定。两种植物黎明 - 黄昏可滴定酸度的60%至70%来自呼吸产生的CO₂内部循环，从绝对值来看，旱季的循环减少，这与干旱胁迫下预期的变化趋势相反。在雨季和旱季，循环都是两种植物碳平衡的重要方面。叶片Na浓度高于陆地盐胁迫CAM植物的报道值。在黑暗期，弯叶铁兰叶基部的果糖和葡萄糖含量下降，但叶片较远区域则不然。洪堡氏堇花兰夜间蔗糖含量下降，甘露醇也是叶片的重要成分。弯叶铁兰木质部汁液最大张力从雨季的0.38±0.09 MPa增加到旱季的仅0.55±0.06 MPa，这些值远低于同一地点陆地灌木和草本植物的值。这两种附生植物利用CAM并结合不同的形态适应机制，以在西耶内加·埃尔·奥西昂纳尔全年保持生长，但似乎弯叶铁兰在旱季维持碳获取方面具有更好的生理特性。
