| Title | Photosynthetic induction in leaves of co-occurring Fagus lucida and Castanopsis lamontii saplings grown in contrasting light environments |
| Author | Bai, Kun-dong |
| Publication | TREES-STRUCTURE AND FUNCTION |
| Year | 2008 |
| Volume | 22 |
| Issue | 4 |
| Corresponding Author | Cao, KF |
| Abstract | Photosynthetic induction times and photoinhibition in relation to simulated sunflecks (sudden increase of irradiance from 20 to 1,500 mu mol m(-2) s(-1)) were examined in leaves of co-occurring Fagus lucida (a deciduous tree) and Castanopsis lamontii (an evergreen tree) saplings grown either in a beech forest understory or in an adjacent open site during a late rainy season. Two hypotheses were tested: (1) understory leaves would display faster photosynthetic induction times and greater photoinhibition than open-grown leaves; and (2) evergreen species would have slower photosynthetic induction times and lighter photoinhibition than deciduous species. Times to reach 90% of maximal CO2 assimilation rate (t(90%A)) and stomatal conductance (t(90%gs)) did not differ between species, but showed faster by 3-5 min in open-grown leaves than understory leaves due to higher initial stomatal conductance (g(s) (initial)) and induction state 1 min into simulated sunflecks (IS1min) in the former. Our analysis across the published data on photosynthetic induction of 48 broad-leaved woody species again revealed the negative correlations between t (90%A) and either g (s initial) or IS1min, and the similarity of t(90%A) and either g(s) initial or IS1min, and the similarity of t(90%gs) and t(90%gs) between evergreen and deciduous species. Measurements of maximum PSII photochemical efficiency (F-v/F-m) indicated that photoinhibition occurred in saplings in any of the growth habitats during sunfleck-induced photosynthetic induction. Despite no interspecific differences in the degree of photoinhibition, understory leaves of both species suffered heavier photoinhibition than open-grown leaves, as indicated by a stronger decrease of F (v)/F (m) in the former. Dynamic changes in the quantum yields of PSII photochemistry and Delta pH- and xanthophyll-regulated thermal dissipation and adjustments in the partitioning of electron flow between assimilative and non-assimilative processes were functional to resist photoinhibition. However, such photoinhibition, together with stomatal and biochemical limitations, would decrease carbon gain during simulated sunflecks, particularly in understory leaves. |
