SEASONAL PATTERNS OF ACID FLUCTUATIONS AND RESOURCE STORAGE IN THE ARBORESCENT CACTUS OPUNTIA-EXCELSA IN RELATION TO LIGHT AVAILABILITY AND SIZE

被引:30
作者
LERDAU, MT
HOLBROOK, NM
MOONEY, HA
RICH, PM
WHITBECK, JL
机构
[1] Department of Biological Sciences, Stanford University, Stanford, 94305-5020, CA
关键词
CRASSULACEAN ACID METABOLISM; LIGHT AVAILABILITY; OPUNTIA-EXCELSA; RESOURCE STORAGE; TROPICAL DECIDUOUS FOREST;
D O I
10.1007/BF00317359
中图分类号
Q14 [生态学(生物生态学)];
学科分类号
071012 ; 0713 ;
摘要
We investigated relationships between light availability, diel acid fluctuation, and resource storage in the arborescent cactus Opuntia excelsa growing in western Mexico. We compared canopy and understory individuals from a deciduous forest as well as open-grown plants of the same approximate size as those in the understory. During the wet season light availability and daily fluctuations in titratable acidity (an index of carbon uptake) were lower in the understory than in unshaded habitats. In the dry season all plants had reduced levels of acid fluctuation, with the smallest individuals, regardless of habitat, showing the greatest reduction. These data suggest that light availability in the forest understory constrains carbon assimilation during the wet season, but that a factor associated with plant size, possibly water status, limits carbon gain during the dry season. Plants in all habitats remained physiologically active for at least five months into the dry season. We suggest that this was possible due to the maintenance of constant concentrations of water and nitrogen in the photosynthetically active chlorenchyma. Parenchyma in terminal cladodes showed a different seasonal pattern of resource storage; water content and nitrogen concentration were reduced from the wet to the dry season in the parenchyma. Using the parenchyma to supply photosynthetic tissues during times of reduced resource availability allows O. excelsa to assimilate carbon during times of the year when most other trees in the forest are leafless.
引用
收藏
页码:166 / 171
页数:6
相关论文
共 34 条