Parents of Norway Spruce Adjust the Performance of Their Progeny According to Changes in Climate and Weather Conditions During Female Flowering

Abstract

Several independent tests have shown that climate and weather conditions during sexual reproduction influence the adaptive properties of Picea abies progenies. This phenomenon is expressed in seed orchards established by moving parent trees, propagated as grafts, from north to south, from high to low elevation, or from outdoor to indoor greenhouse conditions. The progenies exhibit delayed dehardening and flushing in the spring, later growth cessation of leader shoots in the summer, delayed bud-set, higher frequency of lammas shoots and delayed development of frost hardiness in the autumn compared to their siblings reproduced in a colder native environment. The altered performance is persistent; data indicate that the changed phenology lasts for more than 17 years from seeds. The environmental signal is transmitted from parents to offspring during one or several reproductive stages in the female flowers. We suspect an existence of a regulatory mechanism which senses the changes in temperature and/or photoperiod, and then modifies the expression of genes controlling adaptive traits in the progeny. Regardless of type of mechanisms involved, these observations have affected our interpretation of provenance variation. The described phenomenon should be accounted for when predicting long term effects of global warming in both managed and natural boreal forests.