Embryo development and ovule growth monitoring of Prunus domestica late-ripening cultivar 'Elena' compared to medium late-ripening cultivar 'Topper'

In 2008, the late-ripening Prunus domestica cultivar ‘Elena’ was compared with the medium late-ripening cultivar ‘Topper’ regarding the embryo and ovule development by means of weekly microscopic observation and ovule length measurement. Both cultivars bloomed in Hallbergmoos, Germany, at the same time in calendar week 17. The embryo development of the cultivar ‘Topper’ started one week earlier than ‘Elena’ and stayed continuously equally ahead. The embryo started to develop after the ovule and endosperm reached a particular size. During embryo development, the ovule growth almost stagnated. Therefore, there is a relationship between embryo growth and ovule development. The obtained results indicate for cultivar ‘Topper’ the ability of contemporary ovule growing and embryo development at the beginning of the embryo development phase, which could be a reason for the earlier ripening time of ‘Topper’ compared to ‘Elena’. We found a cultivar specific variance in ovule growth and embryo development procedure.