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The Effects of Shoot Water Status on Some Photosynthetic Partial Processes in Sitka Spruce
Author(s) -
BEADLE C. L.,
JARVIS P. G.
Publication year - 1977
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1977.tb01513.x
Subject(s) - photosynthesis , photosystem ii , shoot , botany , carbon fixation , stomatal conductance , photosystem i , biology , cutting , horticulture , chemistry
Clonal cuttings of Picea sitchensis (Bong.) Carr. were grown in a controlled environment and, after completion of shoot extension and maturation, subjected to a drying cycle. Photosynthesis and stomatal conductance were measured in situ using 14 CO 2 and a porometer, respectively. Shoot water potential was measured with the pressure chamber. Photosystem and carboxylase activities of chloroplast preparations were measured in vitro . A considerable fall in photosynthetic rate occurred at low water potential. This was associated with stomatal closure and a decrease in CO 2 transfer or fixation processes in the mesophyll. Little change in activity of photosystem I, photosystem II, and ribulose 1,5‐diphosphate carboxylase was detected during the drying cycle. Any decline in activity of the photosynthetic partial processes in vivo under severe water stress (Ψ < – 30 bar) was probably masked in vitro as a result of rehydration prior to assay.