Studies on Leaf Formation in Rice Plants : IV. Some experiments revealing the role of processes in leaf formation.

[摘要] Stem tip culture in vitro, shading and root cutting were adopted to detect the role of processes involved in leaf formation of rice plants. When cultured in vitro, the larger shoot apices taken from older plants made longer leaf blades than those developed from smaller shoot apices of younger ones. The same phenomena were observed when length of leaf blade developed from larger shoot apices of sparsely-grown or of nitrogen fertillzed plants (see previous paper) were compared with those developed from smaller ones of densely-grown or non-nitrogen fertilized plants. These results show that size of shoot apices primarily determines size of leaves. The leaf primordium which had just appeared at the foot of a shoot apex at the time of transplanting the stem tip into culture medium, grew into a leaf with less number of larger and more of smaller vascular bundles as compared to the next older one just below it. This shows that the surgical treatment at the time of transplanting affects the differentiation of each bundles of different primordia, as the stage of differentiation of both types of vascular bundles are different (see previous paper). Shading at the time of emergence of a given leaf increases sheath length of the leaf and blade length of the adjacent younger leaf. This is attributed to the activity of intercalary meristem occurring at the sheath base of the emerging leaf and blade base of the adjacent younger leaf respectively. Root cutting at the time of emergence of a given leaf decreases sheath length of the adjacent older leaf, which had almost fully expanded, blade length of the emerging leaf, and blade width of the adjacent younger leaf. The effects on length of sheath and blade are explained in the same way as in the case of shading. The effect of root cutting on the blade width is attributed to the activity of ground meristem working before a leaf begins to emerge, and this meristem was affected by the treatment. From these observations and from the results of previous papers, it is concluded that the processes of leaf formation in rice plants can be demonstrated as follows: Shoot apex : Size and structure of a leaf is primarily determined. P1-P2 : Number of larger vascular bundles of the leaf is determined. P2-P3 : Number of smaller vascular bundles of it is determined. P3-P4 : Blade width of it is determined. P4-P5 : Blade length of it is determined. P5-P6 : Sheath length of it is determined. where the successsive stages of leaf development are designated as P1, P2, P3, P4, P5 and P6 respectively, showing P1 the youngest leaf primordium and P6 the oldest almost fully expanded leaf (see previous paper).

[学科分类] 农业科学（综合）