Desiccation Tolerance of Papaver dubium L. Pollen during Its Development in the Anther: Possible Role of Phospholipid Composition and Sucrose Content.

Developing pollen of Papaver dubium L. becomes functional and desiccation tolerant at approximately 2 to 1 days prior to anthesis, coincident with degradation of starch and a doubling of the amount of sucrose, the primary soluble carbohydrate present. When anthers were taken from flower buds at 3 days before anthesis, pollen dehisced upon exposure to the ambient air. This dried pollen did not fluoresce with the vital stain fluorescein diacetate, had increased leakage of K(+), and did not swell properly in a germination medium. In contrast, pollen became functional and desiccation resistant when these young anthers were first incubated in a water-saturated atmosphere for 30 hours. Phospholipid composition revealed no major differences over the last 3 days of development. When this immature pollen was liberated mechanically and allowed to mature in humid air, starch degraded and sucrose content nearly doubled, and the grains became largely functional and dehydration tolerant. Large unilamellar vesicles were prepared from isolated phospholipids to study dehydration-induced fusion and leakage. When dried in the presence of increasing concentrations of sucrose, vesicle integrity was progressively retained. These data indicate that pollen maturation during the last 3 days of development occurred independently from the parent plant. Sucrose may play an essential role in the acquired tolerance to severe dehydration.