Utilization of Exogenous Carbohydrates for Tube Growth and Starch Synthesis in Pine Pollen Suspension Cultures

Abstract

AbstractPine pollen (Pinus mugo) grown in suspension cultures readily utilize exogenous carbohydrates for tube growth and starch synthesis: these processes are not influenced by β‐indolylacetic acid, gibberellic acid, kinetin and abscisic acid. It appears that the free sugars of the female gametophyte, namely sucrose, raffinose, and stachyose and their monosaccharide constituents, are the best substrates for growth and polysaccharide synthesis. The oligosaccharides are hydrolysed to their monosaccharide constituents before they are taken up. A preferential uptake of fructose is noted. Non‐metabolizable sugars are not taken up. The data presented establish that tube growth, except for the initial growth phase, can be determined by the availability of exogenous carbohydrates.Measurements of some of the key enzymes in carbohydrate metabolism show that the enzymes were present in the ungerminated pollen grain, and that the enzyme activity increased severalfold during tube growth. The increase in enzyme activity was prevented if inhibitors of protein synthesis were present in the medium.