Mulkey Stephen S, Smith Alan P, Wright S Joseph
Department of Biology, University of Missouri-St. Louis, 63121-4499, St. Louis, MO, USA.
Smithsonian Tropical Research Institute APO, 34002-0011, Miami, FL, USA.
Oecologia. 1991 Oct;88(2):263-273. doi: 10.1007/BF00320821.
Demography and physiology of two broad-leaved understory tropical herbs (Marantaceae) were studied in gaps and shaded understory in large-scale irrigated and control treatments during the dry season at Barro Colorado Island (BCI), Panama. Because photosynthetic acclimation potential may not predict light environments where tropical species are found, we studied a suite of physiological features to determine if they uniquely reflect the distribution of each species. Calathea inocephala and Pleiostachya pruinosa grow and reproduce in gaps, persist in shade, and have equivalent rates of leaf production. Calathea leaves survived 2 to 3 times as long as leaves of Pleiostachya and plants of Pleiostachya were 6 to 8 times more likely to die as plants of Calathea during 3.5 years of study. Pleiostachya had lowest survival in shade and when not irrigated during the dry season, while Calathea survived well in both habitats and both treatments. Pleiostachya had higher photosynthetic capacity and stomatal conductance than Calathea and acclimated to gaps by producing leaves with higher photosynthetic capacity. Calathea had lower mesophyll CO concentrations than Pleiostachya. Both species had similar dark respiration rates and light compensation points, and water-use and nitrogen-use efficiencies were inversely related between species. Species showed no differences in leaf osmotic potentials at full turgor. Calathea roots were deeper and had tuberous swellings.Leaf-level assimilation and potential water loss are consistent with where these species are found, but photosynthetic acclimation to high light does not reflect both species' abilities to grow and reproduce in gaps. Pleiostachya's gap-dependent, rapid growth and reproduction require high rates of carbon gain in short-lived leaves, which can amortize their cost quickly. High rates of water loss are associated with reduced longevity during drought. Calathea's roots may confer greater capacitance, while its leaves are durable, long-lived and have lower water loss, permitting persistence long after gap closure.
在巴拿马巴罗科罗拉多岛（BCI）旱季期间，对两种阔叶林下热带草本植物（竹芋科）在大规模灌溉和对照处理的林窗和遮荫林下的种群统计学和生理学进行了研究。由于光合适应潜力可能无法预测热带物种所处的光照环境，我们研究了一系列生理特征，以确定它们是否能独特地反映每个物种的分布。头状竹芋和粉状多穗竹芋在林窗中生长和繁殖，在遮荫处存活，且叶片产生速率相当。在3.5年的研究期间，头状竹芋的叶片存活时间是粉状多穗竹芋叶片的2至3倍，粉状多穗竹芋植株死亡的可能性是头状竹芋植株的6至8倍。粉状多穗竹芋在遮荫处以及旱季不灌溉时存活率最低，而头状竹芋在两种生境和两种处理下都存活良好。粉状多穗竹芋比头状竹芋具有更高的光合能力和气孔导度，并通过产生具有更高光合能力的叶片来适应林窗环境。头状竹芋的叶肉二氧化碳浓度低于粉状多穗竹芋。两个物种的暗呼吸速率和光补偿点相似，物种间水分利用效率和氮利用效率呈负相关。在完全膨压下，两个物种的叶片渗透势没有差异。头状竹芋的根更深且有块茎状肿胀。叶片水平的同化作用和潜在水分损失与这些物种的分布位置一致，但对高光的光合适应并不能反映两个物种在林窗中生长和繁殖的能力。粉状多穗竹芋依赖林窗的快速生长和繁殖需要在短命叶片中获得高碳同化率，这可以迅速分摊其成本。高水分损失率与干旱期间寿命缩短有关。头状竹芋的根可能赋予更大的持水力，而其叶片耐用、寿命长且水分损失较低，使其在林窗关闭后仍能长期存活。
