Exogenous Substrate Utilization and Fermentation by the Pollen of Pinus ponderosa.

Abstract

When pollen of Pinus ponderosa is germinated in water, the main endogenous substrate during the first 72 hrs. is sucrose. Subsequently, the starch is used as evidenced by the disappearance of the starch grains. When starch-free pollen is fed D-xylose, D-glucose, D-fructose, D-galactose, sucrose, maltose, lactose, cellulose and raffinose, stainable polysaccharide grains reappear. These same sugars are respired. D-ribose and D- and L-arabinose are without effect, while D-mannose inhibits both growth and respiration. The fermentative capacity of the pollen was established by the anaerobic utilization of endogenous sucrose, an R.Q. of 12 during the metabolism of pyruvate by fluoride-inhibited pollen, and a 15% Pasteur effect. Pollen respiration is inhibited completely by cyanide and 32% by carbon-monoxide. The latter is light reversible. The utilization of external carbohydrates and the fermentative capacity are characteristics of the pollen which might be expected on the basis of the life history of pollen.