Viability of plum ovules at different temperatures

The viability of ovules was studied in five plum cultivars under laboratory conditions at four constant temperatures: 5 degreesC, 10 degreesC, 15 degr eesC and 20 degreesC and under field conditions over two years. During 10 d ays from the onset of full broom, ovule viability in cvs 'Cacanska Rana','C acanska Najbolja' and 'Cacanska Lepotica' was between 80-100 % at the tempe ratures of 5 degreesC, 10 degreesC and 15 degreesC, in both years. Ln the s ame period, ovule viability in cvs 'Wangenheims Fruhzwetsche' and 'Pozegaca ' was lower, but never below 50%. At the constant temperature of 20 degrees C, all plum cultivars showed a decline in longevity of ovule viability, whi ch was pronounced in cv. 'CaEanska Rana'. During the 10 days from the onset of full bloom, ovule viability in all five plum cultivars under field cond itions showed a high viability, which approximated to the ovule viability o f the cultivars at the constant temperatures of 5 degreesC, 10 degreesC and 15 degreesC, in both years. Determination of the longevity of ovule viabil ity in the mentioned plum cultivars is of great importance due to its effec t on the effective pollination period and fertilisation success. This paper deals in detail with the interrelations between the temperature effects on ovule viability, pollen tube growth and fertilisation, as well as on fruit setting.