Effects of light, temperature, and water stress on the photosynthesis and respiration rates of leaves in four oak species
1989
Han, S.S. | Kim, H.S. (Kangwon National Univ., Chunchon (Korea R.). Coll. of Forestry)
The present study has been designed to define the effects of photosynthetically active radiation, leaf temperature, and water stress on photosynthesis and respiration of leaves of four oak species (Quercus mongolica, Quercus aliena, Quercus variabilis, and Quercus serrata). The estimated light compensation points at which Pn approached zero were 38, 24, 20, and 18 micro Em** (-2) s** (-1) for Q. aliena, Q. variabilis, Q. mongolica, and Q. serrata, respectively. The transpiration rates of Q. variabilis and Q. serrata leaves were slightly higher than those of Q. mongolica and Q. aliena leaves at various photosynthetically active radiations (PAR), but cuticular transpiration rates at dark were similar in four oak species. The optimum photosynthesis occurred at 25deg C in Q. aliena, Q. variabilis, and Q. serrata leaves, but 20deg C in Q. mongolica leaves. In four oak species, the net photosynthesis approached zero at about 40deg C. The dark respiration rates of leaves exhibited the following ranking of species : Q. variabilis Q. mongolica Q. aliena Q. serrata. The maximum productive efficiency (Pg/Rd) of leaves occurred highest in Q. serrata at 20deg C, then in Q. mongolica at 20deg C, then in Q. aliena at 25deg C, and finally in Q. variabilis at 15deg C. The decrease of net photosynthesis in Q. serrata began at about -1.2 MPa, and then approached zero at -2.9 MPa of leaf water potential. The decrease of net photosynthesis began at 3 % of water loss, and then approached zero at 17.5 % of water loss. As indicated by tissue-water relations parameters, it may be suggested that Q. aliena and Q. variabilis are more tolerant and favored on xeric forest soils than Q. mongolica and Q. serrata
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