Paraheliotropic Leaf Movement of Bush Bean in Response to Water Availability and Air Temperature

in HortScience
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  • 1 Dept. of Natural Resource Sciences, Macdonald Campus of McGill Univ., 21,111 Lakeshore Road, Ste Anne de Bellevue, Quebec H9X 3V9, Canada.

Paraheliotropic leaf movements of bush bean were studied in relation to water availability, ambient temperature, leaf water potential, and stomatal conductance in a growth chamber. Unifoliate leaf angle from the horizontal (LA), stomatal conductance (G), and leaf water potential (WP) were measured at noon to minimize the effect of leaf movements due to circadian rhythm. Photoperiod and light intensity on the foliage were kept constant at 14 h, and 200 μmol·m–2·s–1, respectively, throughout the measurements. Negative correlations were obtained between water availability (WA) and LA (R = –0.93), and WP and LA (R = –0.85), whereas positive correlations were shown between WA and WP (R = 0.90), WA and G (R = 0.90), and WP and G (0.84) at 35C air temperature. Similar correlations were observed at 25C between WA and LA (R = –0.91), WP and LA (R = –0.79), WA and WP (R = 0.91), WA and G (R = 0.68), and WP and G (R = 0.76). Air temperature significantly (P ≤ 0.01) affected leaf movements.

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