Low night temperatures change whole-plant physiology and increase starch accumulation in Chrysanthemum morifolium

Abstract

SummaryOvernight changes in carbohydrate levels and the uptake of 15NO3–, photosynthesis, and plant morphology were investigated in Chrysanthemum morifolium with the aim of identifying the first limiting factor to influence plant growth and maintenance at low night temperatures. Plants were grown in long-day conditions in an aerated nutrient solution culture system placed in three identical climate chambers. Night/day temperature treatments were 18°/18°C (control), 12°/18°C, and 8°/18°C, respectively. Chrysanthemum morifolium had the same dry matter (DM) production in the three treatments; however, plants grown with low night temperature treatments formed fewer leaves and their total leaf area decreased. In contrast, low night temperatures increased leaf DM content at the expense of root DM content. This was explained, in part, by starch accumulation, which occurred because the starch synthesised during the photoperiod did not disappear during the dark period. Low night temperatures decreased the N concentration in plants; however, this reduction was limited and explained, in part, by starch accumulation in the leaves. Daily plant NO3– uptake was not affected by low night temperatures, although the NO3– uptake rate was lower during the night when plants were grown at 8°C, possibly due to a decrease in transpiration. Furthermore, low night temperatures had no effect on stem length, in contrast to previous literature. No explanation could be found; however, the short duration of the experiment might explain this. The present results provide new information on the limits for growing chrysanthemums and other floricultural crops in a dynamic climate-control system with low temperatures during the night, and in other periods when plants are less active.