Changes in cytoplasmic carbohydrate content during Helleborus pollen presentation

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Abstract
Pollen grains of Helleborus foetidus and H. bocconei were exposed to low temperature treatments to simulate the natural events in pollen presentation of these two winter flowering species and to analyze the pollen carbohydrate content (glucose, fructose, sucrose and starch). In both species, cytoplasmic polysaccharides, monosaccharides and sucrose were found, while only Helleborus foetidus contained starch. Polysaccharide, sucrose and monosaccharide content varied as low temperature exposure time varied, a decrease in temperature decreases polysaccharide content and increases sucrose and monosaccharides. The relative quantities of the various types of carbohydrates were not affected by variations in the naturally occurring thermal cycles. Treatments did not greatly affect pollen viability. Although the occurrence of carbohydrates in pollen is known since many years, their function is still unclear. The findings of this research suggest a role of cytoplasmic pollen carbohydrates in resistance to low temperature exposure. The inter-conversion of carbohydrate type may be an adaptation for sustaining viability during pollen presentation that is particularly important for a winter flowering species such as Helleborus foetidus and H. bocconei .