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Water stress, carbon dioxide, and light effects on sucrosephosphate synthase activity in Phaseolus vulgaris
Author(s) -
Vassey Terry L.,
Quick W. Paul,
Sharkey Thomas D.,
Stitt Mark
Publication year - 1991
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.1399-3054.1991.tb01709.x
Subject(s) - phaseolus , sucrose phosphate synthase , sucrose , cycloheximide , chemistry , enzyme assay , photosynthesis , carbon dioxide , horticulture , enzyme , botany , food science , sucrose synthase , biochemistry , biology , protein biosynthesis , invertase , organic chemistry
The characteristics of sucrose‐phosphate synthase (SPS; EC 2.4.1.14) activity in leaves of Phaseolus vulgaris L. cv. Linden was studied in plants subjected to water stress and various CO 2 and light treatments. When water was withheld for 3 days causing mild water stress (–0.9 MPa), the activity of SPS measured in crude extracts was reduced ca 50%. The effect of water stress was most evident when the enzyme was assayed with saturating amounts of its substrates fructose 6‐phosphate and UDP glucose. Placing a water‐stressed plant in an atmosphere containing 1% CO 2 reversed the effect of water stress on SPS activity over 5 h even though the water stress was not relieved. Holding unstressed leaves in low CO 2 partial pressure reduced the extractable activity of SPS. After 1 h of low CO 2 treatment the effect of low CO 2 could be reversed by 20 min of 5% CO 2 . However, after 24 h of low CO 2 treatment, less SPS activity was recovered by the 20 min treatment. The cytosolic protein synthesis inhibitor cycloheximide prevented the slow recovery of SPS activity, but did not affect the rapid recovery of SPS. We conclude that the effect of water stress on SPS activity was a consequence of the inhibition of photosynthesis caused by stomatal closure. Responses of Phaseolus vulgaris SPS to light were similar to the response to low CO 2 in that the effects were most pronounced under V max assay conditions. This is the first report of this type of light response of SPS in a dicotyledonous species.