Role of Anther on Pollen Embryogenesis in Anther Culture of Nicotiana tabacum L.

Abstract

In order to define the role of anther on the pollen embryogenesis in anther culture of tobacco, the presence or absence of starch granules, amount of soluble sugars and content of free amino acids in cultured anthers were investigated through comparing with those in in vivo anthers. Starch granules in the tissues of cultured anthers disappeared rapidly, and the amount of soluble sugars also decreased soon after the onset of culture. Only a very small amount of soluble sugars was detected during the first 6 days of culture although sucrose was supplemented to the medium. On the 8th day of anther culture, the amount of soluble sugars, especially sucrose increased. It is known that pollen embryogenesis of tobacco can be induced under condition of sugar starvation in the culture medium. These results indicate that in the initial period of culture, the conchtions of the anther loculus are favorable for the induction of pollen embryogenesis. From the results of free amino acid analysis of cultured anthers, it was revealed that large amounts of glutamine and asparagine were present in cultured anthers on the 10 th day of culture when cell division leading to embryo formation began in cultured anther, although no amino acid was supplemented to the medium. It has been reported that certain amino acids such as glutamine and asparagine were essential to undergo cell dlvision leading to embryo formation from pollen grains of tobacco. Therefore, the results indicate that the amino acids required for embryo formation are supplied to pollen grains by cultured anthers. The present results revealed that the factors required for the process of pollen embryogenesis were successively provided to pollen grains by cultured anthers. It is concluded that satisfactory conditions of cultured anthers are the key points of the efficient formation of pollen embryos in anther culture of tobacco.