Southern Research Station

Title: Photosynthesis and xanthophyll cycle-mediated photoprotection in leaves of Quercus rubra and Q. alba seedlings of different light environments

Author: Sung, Shi-Jean S.; Xu, Dianpeng; Kormanik, Paul P.; Black, Clanton C.

Date: 1997

Source: Diversity and adaptation in oak species; Proceedings of the second meeting of working party 2.08.05, genetics of Quercus, of the International Union of Forest Research Organizations; 1997 October 12-17;. University Park (State College), PA.: 288-297.

Station ID: --

Description: Two and three years after the outplanting of 1-0 northern red oak (Quercus rubra, NRO) and white oak (Q. alba, WO) nursery stocks, the highest net photosynthetic rates (A_max) were observed from seedlings growing on a clearcut site, followed by those under a pine stand. Both NRO and WO seedlings under a hardwood stand had A_max less than 10 percent of the full sun seedling A_max Oaks grown under hardwoods increased their A_max more in response to sunflecks than those under a pine stand. Besides NRO and WO seedlings, leaves of several hardwood seedlings and shrubs grown under different light environments were analyzed for pigments and the operation of the xanthophyll cycle. All species investigated shared the following characteristics: higher contents of chlorophyll a+b, a-carotene, lutein, and neoxanthin; smaller xanthophyll cycle pool (sum of violaxanthin V, antheraxanthin A, and zeaxanthin Z); and lower ratios of Z+A to Z+A+V in leaves of understory plants than leaves of the same species growing in full sun. The diurnal xanthophyll cycle (i.e., high Z+A/Z+A+V ratio in midday and low Z+A/Z+A+V ratio near dawn and dusk) was present in leaves of NRO and WO seedlings on the clearcut site. Almost no xanthophyll cycle was operating in understory leaves except that upon sunflecking NRO and WO under hardwoods increased their Z+A/Z+A+V ratio. For every unit of the xanthophyll cycle pool, twice as many chlorophylls must be protected in shade-grown leaves as in sun-grown leaves. The potential use of leaf a-carotene levels in silviculture is discussed.

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Citation

Sung, Shi-Jean S.; Xu, Dianpeng; Kormanik, Paul P.; Black, Clanton C.  1997.  Photosynthesis and xanthophyll cycle-mediated photoprotection in leaves of Quercus rubra and Q. alba seedlings of different light environments.   Diversity and adaptation in oak species; Proceedings of the second meeting of working party 2.08.05, genetics of Quercus, of the International Union of Forest Research Organizations; 1997 October 12-17;. University Park (State College), PA.: 288-297.