Morphological and physical parameters of flower buds of trees of two Japanese pear cultivars grown at three different areas of Southern Brazil, and their relationship with flower bud abortion intensity

This study involved the measurement and analysis of morphological and physical characteristics of the floral buds in Japanese pears (Pyrus pyrifolia Nakai) cvs. Housui and Nijisseiki at three different locations (Vacaria-RS, Pelotas-RS and São Joaquim-SC). The samples were collected on August 18, 1999, and fixed in FAA (10% formaldehyde, 5% acetic acid, 85% alcohol 70) for subsequent analysis. The volume, weight, length, diameter, number of flower primordia of bud, and length, fresh matter, turgid matter and dry matter of inflorescence were determined. Variations were observed in all analyzed parameters, both between locations and cultivars. In the São Joaquim area, both cultivars Housui and Nijisseiki, had a lower number of floral primordia as compared with those of the two other areas. In cv. Nijisseiki, at Pelotas, the length of the inflorescence was larger compared with two other areas. For the cv. Housui, the data show that São Joaquim produced the better bud quality, and this can be related to lower rates of floral bud abortion in those climatic conditions. In contrast to São Joaquim, at Pelotas, the cv. Housui had a different response, mainly in number of primordia, that can be linked to higher rates of floral bud abortion occurring in that area. The results indicate that, the cultivar that has larger values of volume, weight, length and bud diameter, generally presents lower inflorescence lengths and larger numbers of bud primordia. These results possibly explain why some cultivars have higher flower bud abortion rates in areas of low accumulation of chilling, as in Pelotas. In the buds that were grown at Pelotas, a duplication of the inflorescences occurred, causing very large number and less vigorous floral primordia to be formed, an abnormal phenomenon during the flower differentiation phase. At São Joaquim, possibly the low temperatures during the flower differentiation phase are influencing favorably the production of the floral buds. This factor may be the cause of the reduced incidence of floral bud abortion in that area.