Root-zone heating at a night air temperature of 8 degrees C does not decrease starch accumulation in Chrysanthemum morifolium

摘要

To study whether root-zone heating during cold nights could increase root growth and nutrient uptake, plants of Chrysanthemum morifolium were grown in nutrient solution cultures at a day temperature (DT) of 20 degrees C, and four combinations of night air temperatures (NAT) and night root-zone temperatures (NRT) in a controlled climate chamber experiment. The NAT/NRT temperatures of the four treatments were 8 degrees/8 degrees C, 8 degrees/20 degrees C, 20 degrees/8 degrees C and 20 degrees/20 degrees C, respectively. Plants grown at 8 degrees C NAT had increased starch accumulation in the leaves, which explained the increase in leaf dry matter (DM), and which occurred at the expense of stem and root DM. Furthermore, plants grown at 8 degrees C NAT had fewer leaves, reduced leaf area, and shorter stems. Root-zone heating of plants grown at 8 degrees C NAT, did not affect total leaf number, or leaf area, but the root length increased. However, this had no effect on NO3-uptake. Furthermore, root-zone heating did not reduce leaf starch accumulation and the increase in leaf DM. The present results do not support the hypothesis that root-zone heating in chrysanthemum can be used to increase root demand for carbohydrates, and increase the export of carbohydrates from leaves at night, when the night air temperature is 8 degrees C.