Winter Dormancy Depths in Some Woody Species of the Fabaceae Lindl. Family Introduced in Nizhny Novgorod Region

Abstract

Cold acclimatization is a complex process that involves extensive modification of plant metabolism. Woody plants of temperate latitudes undergo a kind of preparation for winter conditions in autumn; as a result they become more tolerant to negative temperatures. Plants reach the maximum frost hardiness in the middle of winter, while they lose the acclimatization hardiness by deacclimatization with the increase of temperature in spring. One of the indicators
of plant adaptation to the new growth conditions is their ability to dynamically move into a state of dormancy and leave it under the certain changes of external conditions. The research purpose was to study winter dormancy depth in some woody species of the Fabaceae Lindl. family (Robinia pseudoacacia L., Amorpha fruticosa L., Caragana arborescens Lam.) in Nizhny Novgorod region. We used detection method of thermally-induced environmental changes to achieve this purpose. The experiment material was represented by annual shoots of the studied species harvested in the central part of Nizhny Novgorod region. The studies were being carried out from November to February for 5 years. After cutting, the shoots were transferred to laboratory conditions (t = 20 °C), where they were placed in the containers with water. The phenological state of shoots and temperature mode were daily recorded. The studies have shown that the interruption timeframe of dormancy significantly influence the transition of the studied introduced species to active metabolism. It was found that, when the steady
negative air temperatures are established in winter, the studied objects form high frost hardiness. This is confirmed by the fact that with the artificial interruption of dormancy and warming acceleration from November to February the objects require a significant amount of active temperatures for transition to metabolism. Caragana arborescens Lam. leaves winter dormancy under growing degree-day of 87…136 °С (depending on the calendar periods of dormancy interruption) that is equivalent to 5…7 days of being in warm conditions at an average ambient temperature from 24 to 25 °С. Amorpha fruticosa L. turns to active metabolism in growing degree-day of 255…378 °C; the same happens with Robinia pseudoacacia L. under 198…476 °C. The data obtained during the research update the fundamental principles of factorial ecology through the demonstration of woody species adaptations of the Fabaceae Lindl. family. They can be used for perspective preliminary assessment of their wide cultivation in Nizhny Novgorod region.