Loss of cold temperature tolerance and reacclimation following warm temperatures in peach

Cold hardiness was measured to -30°C in peach (Prunus persica L.) shoots previously exposed to 4 days of cold (-6.7°C) or warm (16.5°C) temperatures.
Four days of warm exposure caused a 5 to 6°C loss in flower bud hardiness in ‘Harrow Beauty’, ‘Starfire’, and ‘Bailey’ peach trees.
The lethal temperature for 50% (LT50) of the flower buds, estimated from the inflection point, ranged from -23.6 to -25.6°C with cold exposure and from -17.9 to -20.5°C with warm exposure.
Xylem parenchyma hardiness ranged from -25.5 to -25.8°C with little difference due to warm exposure or to cultivar.
Phloem was the hardiest tissue and showed only partial injury at-16.7°C after warm exposure in ‘Starfire’ and ‘Harrow Beauty’ and almost no injury in ‘Bailey’. The cambium in ‘Bailey’ and ‘Starfire’ was partially injured at -30°C in cold-exposed shoots but was hardy to -22.8 to -25.8°C in warm-exposed shoots.
Cambium in ‘Harrow Beauty’ was hardy to -19.7 to -22.6°C and was severely injured at -30°C with no difference between temperature treatments.
In a separate experiment, ‘Reliance’ flower buds exposed to warm temperature for 6 days (20°C) lost 8.3°C in hardiness compared with 6-day exposure to cold (1°C). When a 3-day cold exposure was followed by a 3-day warm exposure, buds lost 4.2°C hardiness.
However, a 3-day warm exposure followed by 3-day cold exposure caused 1.2°C loss indicating that reacclimation had occurred.
A similar pattern occurred in the shoot cambium and phloem but not in the xylem, which showed only minor differences due to the different temperature exposures.

XII International Symposium on Integrating Canopy, Rootstock and Environmental Physiology in Orchard Systems

R.E. Moran

xylem, cambium, phloem, flower bud, Prunus persica, oxidative browning

https://doi.org/10.17660/ActaHortic.2022.1346.15