Tropic leaf movements, photosynthetic gas exchange, leaf delta C-13 and chlorophyll a fluorescence of three soybean species in response to water availability
Wy. Kao et Tt. Tsai, Tropic leaf movements, photosynthetic gas exchange, leaf delta C-13 and chlorophyll a fluorescence of three soybean species in response to water availability, PL CELL ENV, 21(10), 1998, pp. 1055-1062
Midday leaf angle, photosynthetic gas exchange, stable carbon isotope ratio
(delta(13)C), and chlorophyll a fluorescence among three wild soybeans, Gl
ycine soja, G. tomentella and G. tabacina, from habitats with different wat
er availability were examined. Plants grown under low water availability ha
d reduced leaf area, photosynthetic and electron transport rates, more posi
tive delta(13)C values, and more vertical midday leaf angles. The three spe
cies differed in midday leaflet orientation, leaf size, photosynthesis and
fluorescence responses to water availability. The species differences were
consistent with the water availability of their habitat, G. soja, which gro
ws in the wettest habitats, was shown to be the most photosynthetically sus
ceptible to low water treatment and tended to have the most vertical midday
leaflet angles. In contrast, G. tabacina, distributed in the driest habita
ts, had the least vertical midday leaflet angles and the lowest photosynthe
tic sensitivity to low water availability. G. tomentella, inhabiting an int
ermediate habitat, had intermediate midday leaf angles and photosynthetic r
esponses. Our results support the hypothesis that paraheliotropic leaf move
ments respond in concert with photosynthetic characteristics in soybean lea
ves such that water use efficiency is enhanced and the risk of photoinhibit
ion under water stress conditions is reduced.