The effect of pollen performance on low seed fertility in a Greek population of Juniperus excelsa

Abstract

The Juniperus excelsa (Cupressaceae) forest in northern Greece has been facing a documented severe decline of natural regeneration over the last few years. In order to dissect the physiological components of the low regeneration, pollen originated from different sites as well as from trees of different height was investigated in terms of viability and in vitro germination capacity. In addition, embryo development and viability of the first year immature seeds were further assessed. Pollen was found to present high viability (61.5–93.2%) in all sites and tree height classes. However, pollen germination was quite low (maximum germination percentage recorded was 30.2%). The low pollen germination capacity recorded in trees above 6 m in height was reflected in the subsequent low percentages of successful embryo development and viability found in the produced seeds. These results suggest that low seed fertility in Juniperus excelsa is associated with reduced pollen germination, suggesting a complex regeneration mechanism and is considered an additional step in shedding light on the physiological basis of the low natural regeneration of Juniperus excelsa.