Influence of the female flowering environment on autumn frost-hardiness of Picea abies progenies.

Two experiments were designed to test possible effects of photoperiod and temperature during microsporogensis to anthesis on early autumn frost-hardiness of Picea abies progenies. Pollen lots were produced in phytotron rooms and used in crosses in a seed orchard. No biologically important differences in progeny performance were evident either between high and low temperature or between long and short-day treatments, and no significant interaction between photoperiod and temperature was found. In a third experiment, however, an effect of the environment during female flowering was obtained. Crosses performed in early spring (March) inside a heated greenhouse (short day, high temperature) produced progenies which were less hardy than their full-sibs reproduced from crosses indoors (long day, high temperature) and outdoors (long day, low temperature) in May. The most hardy siblings originated from the late-spring outdoor crosses. These results indicate that some stages in reproduction during female flowering, such as female meiosis, pollen tube growth, syngamy, early embryogenesis and embryo competition, may be sensitive to temperature and/or photoperiodic signals which can be transmitted to the progeny. We suspect that the altered performance of the progenies could be due to an activation of a regulatory mechanism affecting the expression of genes controlling adaptive traits. Both the present and earlier results have implications for the genetic interpretation of provenance differences in Norway spruce.