The Study Of Gravitropism And Phototropism On The Moss Funaria Hygrometrica And Polytrichum Juniperinum

Nowadays, studies on gravitropism and phototropism are active aspects in the field of plant physiology, many details of which have been studied. To analyze the possible factors that induce and affect the gravitropism and phototropism, we carried out a series of pilot studies of gravitropism and phototropism on the moss Funaria hygrvmetrica and Polytrichum juniperinum. To our knowledge, this is the first experiment of distribution of amyloplast in protonemas of a kind of moss that has no gravitropism, of phototropism of moss protonema affected by exogenetic auxins, and of gravitropism and phototropism of moss stem. All experimental results showed:1. In darkness, protonemal filaments of F. hygrvmetrica grow negatively gravitropically (upwards), but do not happen on the moss P. juniperinum. Comparing the amyloplast position in protonemal tip cell of P. juniperinum under different conditions, we found the amyloplast plays an important role on negative gravitropism. Many amyloplasts accumulated in zone II and the amyloplasts in zone III, which move weakly, possibly, are the main reasons that the protonemas of P. juniperinum have no negative gravitropism in the dark.2. In the unilateral white light (80Lux), protonemal filaments of F. hygrometrica grow positively phototropically (toward the light). We found exogenetic IAA and ZT facilitate the positive phototropism of protonemas of F. hygrometrica, while ABA constraints it, but markedly randomizes growth direction.3. Unilateral red light (80Lux) induces both positive and negative phototropism of F. hygrometrica mediated possibly by two photoreceptor, one arouses positive phototropic response, the other arouses negative positive phototropic response. Only positive phototropism was detected on the P. juniperinum. Comparing the phenomena of protonemas of the two mosses, we guess the movement of chloroplast in protonema may play a key role.4. Protonemas and stems of F. hygrometrica have more obvious phototropic response in the white light than the red light by comparing the time and intensity of the reaction.5. Stems of F. hygrometrica grow negatively gravitropically (upwards) in the dark, but no negative gravitropism be detected and positive phototropism predominated in the moderate unilateral white or red light (400Lux). Strong unilateral red light (1000Lux) reversed the gravitropism, changing it from negative to positive.