title: Costs and benefits of photosynthetic light acclimation by tree seedlings in response to gap formation.
abstract: Some shade leaves increase their photosynthetic capacity (P (max)) when exposed to a higher irradiance. The increase in P (max) is associated with an increase in chloroplast size or number. To accommodate those chloroplasts, plants need to make thick leaves in advance. We studied the cost and benefit of photosynthetic acclimation in mature leaves of a tree species, Kalopanax pictus Nakai, in a cool-temperate deciduous forest. Costs were evaluated as the additional investment in biomass required to make thick leaves, while the benefit was evaluated as an increase in photosynthetic carbon gain. We created gaps by felling canopy trees and examined the photosynthetic responses of mature leaves of the understorey seedlings. In the shade, leaves of K. pictus had vacant spaces that were not filled by chloroplasts in the mesophyll cells facing the intercellular space. When those leaves were exposed to higher irradiance after gap formation, the area of the mesophyll surface covered by chloroplasts increased by 17% and P (max) by 27%. This increase in P (max) led to an 11% increase in daily carbon gain, which was greater than the amount of biomass additionally invested to construct thicker leaves. We conclude that the capacity of a plant to acclimate to light (photosynthetic acclimation) would contribute to rapid growth in response to gap formation.
authors.affiliation: Graduate School of Life Sciences, Tohoku University, Aoba, Sendai 980-8578, Japan. roguchi@biol.s.u-tokyo.ac.jp
authors.forename: R
authors.initials: R
authors.lastname: Oguchi
authors.forename: K
authors.initials: K
authors.lastname: Hikosaka
authors.forename: T
authors.initials: T
authors.lastname: Hiura
authors.forename: T
authors.initials: T
authors.lastname: Hirose
mesh_terms: D000064:Acclimatization / Q000502:physiology* / Q000528:radiation effects*; D018533:Biomass; D002244:Carbon / Q000378:metabolism; D003198:Computer Simulation; D036882:Kalopanax / Q000254:growth & development / Q000378:metabolism* / Q000528:radiation effects*; D008954:Models, Biological; D010788:Photosynthesis / Q000528:radiation effects*; D018515:Plant Leaves / Q000378:metabolism / Q000528:radiation effects; D036226:Seedlings / Q000378:metabolism / Q000528:radiation effects*; D013472:Sunlight; D013997:Time Factors
chemical_list: D002244:Carbon