COLD DAMAGE IN FRUIT BUD TISSUES OF PEAR

A histo-anatomical investigation was carried out on fruit buds, including the basal spur, of cv Abbé Fétel adult pear trees to evaluate the extent and effects of a severe cold spell in January 1985 (below -20°C). Two months following the cold spell sample buds were collected every 10 days up to initial flowering for a total of 4 samplings.

The stereomicroscope evidenced a 98% rate of damaged buds in the first and 100% in the following samplings.
The damaged buds were classified as to increasing injury: A undamaged, B browned basal pith, C browned basal pith and vascular tissues, and D necrotic.
Most of the buds, ranging from 75% in the first to 71% at last sampling, showed i.e. browned basal pith.

Under the microscope these samples showed that the cold increased the number of tannin cells and of cells with calcium oxalate crystals, and caused cellular lysis to form in the pith.
These injuries also extended to the part of the spur at the bud base and sometimes to the parenchyma rays as well as the bark and the border layers of phloem.
Some of the more severely damaged buds, and especially those also with vascular tissue injury, died, while the majority showed a poor, irregular and discontinuous resumption of cambium activity.

These cold-induced injuries may have diminished nutrient reserves and translocation, and caused the increase in necrotic buds and the poor fruit-set of the flowers of the surviving buds (4%).

V International Symposium on Pear Growing

N. Filiti, D. Neri

https://doi.org/10.17660/ActaHortic.1989.256.15