Studies on the Stolon Development in the Potato Plant : II. The relationship between the activities of endogenous auxin and the orientation of the axillary shoot growth in the potato seedlings

[摘要] It was suggested in the previous paper that there might be some causal relation between auxin activity of shoot apex with some younger leaves and orientation of axillary shoot growth in the potato seedlings. In this paper, some experiments were carried out to clarify a relationship between auxin activity of the nodal region of stem and orientation of its axillary shoot growth. The results obtained were summarised as follows; 1. Axillary shoots of cotyledonary node were found to grow downward accompanied with increase of auxin level of the nodal region, that of the 5th node (numbered from the base) horizon-tally with decrease of auxin level and that of the 8th node with low auxin level. So auxin levels of the nodal regions were found to be changed with increasing age of the seedling plants, and the orientation of axillary shoot growth was suggested to be regulated with the changes of auxin levels of the nodal regions. 2. The increment of auxin level of the cotyledonary node was greater than that of apical region of stem. Thus it would be supposed that auxin shown a polar transport might be accumulated at the lower nodal regions. However, the mechanism of orientation of axillary shoot growth regulated by the changes of auxin levels in the nodal regions is not sufficiently explained till now. 3. Low auxin level in the plants and upward orientation of the axillary shoot growth were shown by application of TIBA lanolin paste at 2 mm above and below cotyledonary nodal regions. Decrease in auxin level in the plants was greater in case of the treatment at the cotyledonary nodal regions than in case of the treatment at the 3rd nodal ones, so the sensitivity to TIBA seemed to be weakened with increasing age of the plants. 4. The phenomenon which the axillary shoots grow upward and substitute for the shoot apices is commonly found by decapitating the shoot spex of the potato seedlings. In this experiment, when the shoot apex was decapitated above the 8th node of the 10th leaf stage, decrease in auxin level was shown to be greater in the 7th nodal region than in the 3rd one. However, the growth pattern of axillary shoots did not be changed on each node at five days after the treatment.

[学科分类] 农业科学（综合）