Dag, A., Kennedy-Leigh Centre for Horticultural Research, Faculty of Agriculture, Hebrew University of Jerusalem, PO Box 12, Rehovot 76100, Israel
Eisenstein, D., Kennedy-Leigh Centre for Horticultural Research, Faculty of Agriculture, Hebrew University of Jerusalem, PO Box 12, Rehovot 76100, Israel
Gazit, S., Kennedy-Leigh Centre for Horticultural Research, Faculty of Agriculture, Hebrew University of Jerusalem, PO Box 12, Rehovot 76100, Israel

'Kent' mango (Mangifera indica L.) flowers were sampled in an orchard in the coastal plain of Israel during the 1997 flowering season. 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), reaching a high value only at the end of the season (21 May). The same phenomenon also occurred, albeit with consistently higher rates of effective pollination, when detached flowers, taken from the orchard during the flowering season, 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. At the start of the flowering season, all the pollen was deformed, and later (16 April 1997), when pollen grain shape was normal, only 23% of it was found to be viable by Alexander's staining. 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. Ovule penetration was hampered in orchard pistils, even when phytotron pollen was used for pollination. 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. (C) 2000 Elsevier Science B.V.