1 research outputs found
Utilization and Dissipation of Absorbed Light Energy in the Epiphytic Crassulacean Acid Metabolism Bromeliad Tillandsia Ionantha
This is the publisher's official version, also available electronically from: http://www.jstor.org/stable/10.1086/314130.Past studies of the ability of epiphytic Crassulacean acid metabolism bromeliads to acclimate to different
light levels yield conflicting findings; some indicate that these plants are similar to shade plants whereas others
stress their similarity to sun plants. This study investigates the ability of individuals of Tillandsia ionantha to
acclimate to low or high irradiance. Plants were exposed to 100 and 800 jitmol m~2 s"1 photosynthetic photon
flux density under controlled conditions for 4 wk. Individuals exposed to the lower light level exhibited higher
chlorophyll concentrations and higher photosynthetic rates at low light relative to plants exposed to high
light. Low-light plants also exhibited a greater efficiency in the photochemical utilization of absorbed light
energy and a lower ability to dissipate excess energy nonphotochemically, relative to the plants exposed to
the higher light level. Photosynthetic rates at high light were similar in both sets of plants, reflecting the higher
efficiency of energy conversion in the low-light plants and an apparent saturation of photosynthetic capacity
in the high-light plants. The latter may have resulted from high-light-induced damage to the photosynthetic
apparatus in addition to an increase in nonphotochemical dissipation of excess light energy. The higher capacity
for harmless dissipation of excess light energy in the high-light plants should prove beneficial in plants growing
in exposed locations and subject to drought and nutrient stresses. Thus, the results support and expand those
of previous studies: T. ionantha can acclimate to both low and high light but does so in different ways. Such
flexibility in adjusting the photosynthetic apparatus to varying light levels constitutes a valuable adaptation
to growing throughout the canopy of a host tree