Effect of temperature regime on pollen and the effective pollination of 'Kent' mango in Israel.
Dag A., Eisenstein D., Gazit S.
Author Affiliation: Faculty of Agriculture, The Kennedy-Leigh Centre for Horticultural Research, The Hebrew University of Jerusalem, PO Box 12, Rehovot 76100, Israel.
Scientia Horticulturae 86 : 1-11
Abstract : 'Kent' mango (Mangifera indica) flowers were sampled in an orchard in the coastal plain of Israel during the 1997 flowering season to elucidate the relationship between effective pollination rate and temperature conditions and to determine seasonal variation in the ability of the pollen to germinate and reach the ovule. Effective pollination rate was determined at two stages of the fertilization process: (a) pollen germination on the stigma; (b) pollen-tube penetration into the ovule. Pollination rates were negligible during the first part of the flowering season (31 March to 18 April) but reached a high value at the end of the season (21 May) with an average of 4.9 germinating pollen grains per stigma. The same phenomenon occurred when detached flowers were pollinated and incubated for 24 h at the presumed optimal temperature of 30°C, indicating that the reproductive organs were not fully functionally viable. All the pollen was deformed at the start of the flowering season but Alexander's staining showed at least 23% viability when pollen grain shape started to appear normal (16 April). The functional viability of the pollen and pistils of orchard- and phytotron-grown (22/27°C, night/day) flowers was determined in detached flowers. At the beginning of the flowering season, both orchard pollen and pistils tended to be defective. Orchard pollen germinated poorly, even on phytotron-adapted stigmas (30% of flowers with germinated pollen). Ovule penetration was hampered in orchard pistils, even when phytotron pollen was used for pollination (5% of flowers with pollen tube in ovule). Chilling injury appeared to be responsible for the damage to the reproductive organs of the orchard flowers. The negligible rate of effective pollination found in mango orchards in Israel during a significant part of the flowering season therefore appears to be due to the detrimental effect of cold weather on the pollination and fertilization processes as well as on the functional viability of the male and female reproductive organs.