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Long‐ and short‐term responses of leaf carbohydrate levels and photosynthesis to decreased sink demand in soybean
Author(s) -
MORCUENDE R.,
PÉREZ P.,
MARTÍNEZCARRASCO R.,
MARTÍN DEL MOLINO I.,
SÁNCHEZ DE LA PUENTE L.
Publication year - 1996
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1111/j.1365-3040.1996.tb00462.x
Subject(s) - photosynthesis , shoot , sucrose , chemistry , rubisco , starch , botany , horticulture , sucrose phosphate synthase , phosphate , carbohydrate , ribulose , sucrose synthase , food science , biology , biochemistry , invertase
Axillary buds and the apical portion of shoots of soybean [ Glycine max (L.) Merr. cultivar Turchina] plants were trimmed to investigate long‐term regulation of photosynthesis by sink demand at ambient CO 2 and 22 °C. Also, in intact and trimmed shoots, the CO 2 level was increased to 660 μmol mol −1 and temperature was lowered to 5°C to examine the superimposed short‐term responses of photosynthesis to low sink demand. Under growth conditions, trimming the shoots increased leaf photosynthesis and the levels of sucrose, glucose‐6‐phosphate (G6P) and 3‐phosphoglycerate (PGA), as well as the G6P/fructose‐6‐phosphate (F6P) and sucrose/starch ratios, while it decreased the level of starch and the triose‐phosphate (glyceraldehyde 3‐phosphate and dihydroxyacetone phosphate, TP)/PGA ratio. Photosynthesis enhancement was accompanied by increased chlorophyll contents and ribulose‐l,5‐bisphosphate carboxylase oxygenase (Rubisco) activity. Sink removal consistently increased photosynthesis measured under a variety of conditions (growth CO 2 or a short‐term change to 660 μmol mol ‐1 CO 2 ; growth temperature or a short‐term change to 5 °C), except when low temperature was combined with ambient CO 2 ; the increase in photosynthesis was higher under short‐term elevated CO 2 than at ambient CO 2 . In contrast with its effect at ambient CO 2 , shoot trimming increased the levels of TP and ribulose‐1,5‐bisphosphate (RuBP) and the TP/PGA ratio under high‐CO 2 conditions.