Effect of oscillating temperature on the expression of two aquaporin genes (Pp-δTIPl, Pp-PIP2) involved in regulating intercellular water status in flower buds of peach

We studied the effects of temperature changes on the water status of floral buds in peach during ecodormancy by an analysis of aquaporin (AQP) gene expression and magnetic resonance imaging of the upper part of the bud, the bud base, the bud trace, and the bud cushion. Expression levels of mRNAs of the water channel genes, Pp-δTIPl and Pp-PIP2, in the tonoplast and plasma membrane reflected the temperature oscillations: high temperatures increased mRNA levels and low temperatures decreased them, irrespective of the duration of either treatment. The T₂ relaxation time of the buds, especially in the floral primordia, was significantly longer under oscillating temperature conditions than under a consistently high temperature. The period of high-temperature during the oscillating temperature regime accelerated water flow in the bud, but delayed bud growth. Disruption of the water balance by excessive water in the primordia under oscillating temperatures may be one reason for the delay in bud growth.