EFFECT OF MYCORRHIZAL INFECTION ON THE EA RLY GROWTH OF PROTOCORM IN HABENARIA-RADIATA AOBA AND GYOKURYUKA

To compare the stimulative effects of mycorrhizal infection on the ear ly growth of Habenaria radiata, protocorms of 'Aoba' and 'Gyokuryuka' grown from seeds were inoculated with fungal isolate No. 931202A. The protocorm of 'Gyokuryuka' (2n=64) enlarged faster than those of 'Aoba' (2n=32). The difference is attributed to the following factors: (1) P rotocorms of 'Gyokuryuka' were infected more easily; (2), the conducti ve tissue in the protocorm of 'Gyokuryuka' differentiated and function ed earlier; and (3) the degree of invasion of the fungus into the prot ocorm of 'Gyokuryuka' as measured by the staining intensity of Trypan Blue is much greater. Through these observations, we conclude that the interaction between the infectivity by the different isolate of mycor rhizal fungus and the susceptibility of different cultivars of Habenar ia radiata are decisive factors affecting early seedling growth.