Effects of developmental heat sum on fruit traits of clonal lines of Quercus petraea grown under controlled conditions

An analysis was made of fruit traits of grafted lines of the recalcitrant fruited species Quercus petraea. Plants were grown either inside or outside a glasshouse in Denmark to test the impact of heat sum on fruit development. The results indicated that across the grafted lines, fruits from plants inside the glasshouse were consistently larger with a lower water content. This suggests that fruit development progressed further within phase II of development. This is consistent with findings from earlier, uncontrolled experiments and provides a quantitative explanation for intra-species variability in fruit / seed traits for recalcitrant seeded species.