SEASONAL GAS-EXCHANGE CHARACTERISTICS OF 2 EVERGREEN TREES IN A SEMIARID ENVIRONMENT

Citation
Mk. Owens et Mc. Schreiber, SEASONAL GAS-EXCHANGE CHARACTERISTICS OF 2 EVERGREEN TREES IN A SEMIARID ENVIRONMENT, Photosynthetica, 26(3), 1992, pp. 389-398
Citations number
20
Categorie Soggetti
Plant Sciences
Journal title
ISSN journal
03003604
Volume
26
Issue
3
Year of publication
1992
Pages
389 - 398
Database
ISI
SICI code
0300-3604(1992)26:3<389:SGCO2E>2.0.ZU;2-Z
Abstract
The patterns of net photosynthesis (P(N)), transpiration (E) and condu ctance (g) of a native broadleaf (Quercus virginiana Mill.) and needle -like (Juniperus ashei Buchholz) evergreen tree were evaluated to dete rmine the extent of seasonal variation in gas exchange and the respons e of both species to drought. Gas exchange was evaluated on intact lea ves at monthly intervals from April 1988 through March 1990. Q. virgin iana had higher P(N), E, g and water-use efficiency than J. ashei thro ughout both years. Maximum average P(N) for Q. virginiana occurred in July 1988 (9.58 mumol m-2 s-1) whereas maximum average P(N) for J. ash ei occurred in October 1988 (4.59 mumol m-2 s-1). P(N), E and g increa sed linearly with precipitation for Q. virginiana but were unrelated t o precipitation for J. ashei leaves. Q. virginiana exhibited a 6-fold increase in P(N) and E between dry and wet months whereas J. ashei exh ibited very little change. The ability of Q. virginiana to increase P( N) and E in response to erratic precipitation and to actively photosyn thesize during the winter may provide a competitive advantage over J. ashei and native grasses.