Leaf Temperature and Transpiration of Field grown Cotton and Soybean under Arid and Humid Conditions
Akihiro Isoda and Peiwu Wang*
(Faculty of Horticulture, Chiba University, Matsudo, Chiba
271-8510, Japan; *Shihezi Agricultural and Environmental Institute
for Arid Area in Central Asia, Shihezi, Xinjiang, China)
Cotton (Gossypium hirsutum L.) and soybean (Glycine
max Merr.) cultivars were grown under arid (Urumqi, Xinjiang,
China) and humid (Matsudo, Chiba, Japan) conditions to analyze
their abilities to adapt to arid conditions in terms of transpiration,
leaf movement and leaf temperature. Under the arid condition,
the leaf temperature of the cotton cultivars was higher than that
of the soybean cultivar and the air temperature. There was no
significant difference in leaf temperature among the cotton and
soybean cultivars under the humid condition. The flow rate of
stem sap in the cotton cultivars under the arid condition was
always higher than that in the soybean cultivar, and was largely
affected by vapor pressure deficit (VPD). Under the humid condition,
however, the flow rates of stem sap were lower in the cotton cultivars
than in the soybean cultivars. These results indicate that cotton
can avoid heat stress by the high transpiring ability possibly
supported by well-developed root systems, which leads to higher
drought resistance under the arid condition. Soybean would adapt
to arid conditions by the combination of paraheliotropic leaf
movement and reduced transpiration.