Interrelationship of Temperature, Sugar Concentration, and Pollen Parent on Alfalfa Pollen Germination and Tube Growth In vitro1

Abstract

In vitro pollen studies with alfalfa (Medicago sativa L.) indicated that both sugar concentrations and temperatures affected pollen germination and pollen‐tube growth. Requirements for pollen germination were less specific than those for pollen‐tube growth. At 18 C 60% of more pollen germination occurred on media containing 7, 14, 21, and 28 g of sugar/100 ml water. At temperatures of 24 and 30 C sugar concentrations of 35 and 42 g also produced germinations greater than 60%. At 36 C germination remained high on sugar concentrations of 14 through 42 g sugar, but declined at lesser concentrations.In contrast, maximum pollen‐tube length at 18 C was obtained on media with 7 to 14 g sugar. At 24 C media with 7 through 28 g sugar produced maximum pollen‐tube development. At 30 C pollen‐tube growth of some clones was markedly reduced on low sugar media, whereas other clones were less affected. At 36 C very little pollen‐tube growth was observed.The interaction between sugar concentrations and temperatures suggested to us that alfalfa may have a type of buffering system that allows pollen germination and pollen‐tube growth to occur over a wide range of environments. The data presented in this paper also indicated the existence of temperature‐sensitive genes that may influence pollen‐tube development.