Freeze survival in peach and prune flowers

Abstract

A laboratory study was carried out using field grown peach (Prunus persica) and prune (P. domestica) flowers. The object was to find out why prune flowers are more freeze tolerant than peach flowers. After the flowers are fully open, it was found that the ovaries may still supercool, even with ice crystals present in the flower stem. The mechanics involved were explored with a computer model of the simultaneous heat, water and solute flow in the flower and stem tissue during freezing. Water flow toward growing ice crystals may cause a discontinuity in the liquid phase between the flower stem and the ovary, creating a barrier to nucleation. It was concluded that the prune flowers survive lower temperatures than the peach because the water in their ovaries is more apt to supercool, particularly when the dew point of the air is not reached.