Articles
ONTOGENETIC CHARACTERISTICS IN FLOWERS OF SOME PLUM CULTIVARS
The morphogenetic characteristics of the 13–34 years old trees were analysed with ontogenetic aspects taken into consideration.
From the beginning of flower induction in June, the effect of year as phenotypic factors (maximum and mean temperature, monthly and annual amount of precipitation) produced many significant correlations, so the mean temperatures in June, July, September and Februar as well as the amount of precipitation in July were in significant relation with the most important morphogenetic characters.
In the course of the 22 years, the size of petal changed the least, but the frequency of apistilled, polycarpous and pseudo-staminate flowers showed intensive year effect.
The differentiation in centripetal direction could be proved on the basis of defective flowers, since the destruction of pistil primordia brought about – on a several cultivar average – approximately a two-stamen surplus, irrespective of whether the number of androecia was two-three in the cultivars concerned.
The three periods (1968–1974, 1975–1980 and 1981–1989) that could be continuously examined, called attention to the fact that apart from the consequences of virus infection changes in the flower structure may be due to the age as well as the morphogenetic and fertility conditions of the flowers of plum trees.
Further investigations – now with new cultivars – are still necessary in the case of Prunoideae species, but the results obtained so far, repeatedly call attention to the fact that it is not reasonable to establish a plum orchard consisting of a single (self-fertile) cultivar, particularly when we consider the economic losses of the period of decreasing yields.