林木のつぎ木とその育種への応用 (II) : マツ属のつぎ木植物から得た花粉の機能について

Abstract

本実験はつぎ木したPinus属植物の花粉とそのつぎ穂親木の花粉の形態及び生理的差異を検討するために行われた｡ 1. 供試花粉は次の組合せ樹種から採集した｡ (a) 2年生のP.densiflora, P.Thunbergiiを台木とし, 15~25年生の親木より穂木, P.Banksiana, P.Bungeana, P.densiflora, P.excelsaおよびP.strobusを1954~1956年についだもの｡ (b) 2年生のP.Thunbergiiを台木とし, 3年生の親木より, 穂木, P.Pinasterを1954年ついだもの｡ (c) 実生5年生のP.densiflora, P.Thunbergii｡ 2. 成木 (15 ~ 25年生) からつぎ穂をとつてついだつぎ木花粉の大きさは, そのつぎ穂親木花粉にくらべて幾分小さい傾向が見られたが, その差はわずかであつた｡ 醋酸カーミン染色による花粉稔性は両者ともかなり高かつた｡ その他形態上の差異は認められなかつた｡ 3. 発芽試験は寒天培養と懸滴培養の二法を用いた｡ 一般に発芽は寒天培養の方が懸滴培養よりややよく, 花粉管の伸長においては懸滴培養の方が, 寒天培養よりもよいように思われた｡ 4. 置床後24時間後における寒天培養で, 発芽を見たものはP.Thunbergiiを台木としてついだもののうちP.excelsa, P.strobur及び親木花粉のP.Banksianaで, 置床48時間後には, つぎ木花粉P.excelsaは発芽率79.6%, 花粉管長, 平均39.4μ, P.strobusの発芽率81.2%, 花粉管長, 平均39.4μに達し, そのつぎ穂親木花粉よりもかなり高く, 発芽および伸長は良好であつた｡ つぎ穂親木P.Banksianaの発芽率は40.3%, 花粉管長, 平均26.5μに伸長し, そのつぎ木花粉よりも高く, 発芽および伸長は大であつた｡ 5. 置床72時間後における寒天培地上での花粉の発芽率および花粉管の伸長は, つぎ木花粉ならびにその親木花粉ともかなり高い値をしめした｡ 発芽率はP.Thunbergiiを台木としてついだものから得られた花粉の方が, つぎ穂親木の場合よりやや高く, かつP.densifloraを台木としてついだものの花粉よりも高い傾向が見られた｡ しかしながら, これらの花粉の両者における相異はあまり顕著でないように思われた｡ 6. 若木 (3年生) からつぎ穂をとつてついだ, つぎ木花粉P.Pinasterの花粉の大きさは, そのつぎ木と同年令の花粉にくらべて多少小さかつた｡ 花粉稔性は両者ともかなり高かつた｡ その他形態上の差異は認められなかつた｡ つぎ木花粉P.Pinasterの発芽率は, そのつぎ木と同年令の木からとつた花粉よりややひくかつた｡ しかし花粉管の伸長は両者とも殆ど差は認められなかつた｡ 7. 実生5年生のP.densiflora, P.Thunbergiiの花粉の大きさは, 成木 (約30年生) の花粉にくらべて幾分小さい傾向が見られた｡ 花粉稔性は両者ともかなり高かつた｡ その他形態上の差異は認められなかつた｡ 花粉の発芽率および花粉管の伸長は成木 (約30年生) にくらべてやや低かつた｡ 8. 一般につぎ木花粉はそのつぎ穂親木花粉と同様に, 花粉の発芽率および花粉管の伸長はよいことを認めたから, 交雑用の花粉として使用してもまず支障はないものと考えられる｡ 本研究にさいしいろいろと御指導を賜つた上田教授に対し深甚の謝意を表するとともに, 種々の御助言をいただいた農学部応用植物研究室の渡辺光太郎氏に厚く御礼申げる｡

1. The present work was carried out to examine the morphological and functional characters of the pollen taken from the grafted pine plants. In 1954-1956, Pinus Banksiana, P. Bungeana, P. densiflora, P. excelsa, P. strobus (15-25 years old) and P. Pinaster (3 years old) were grafted on two yeas old P. densiflora or P. Thunbergii; in 1958, the pollens of these trees and their mother trees were collected as materials, and preserved in a cool desiccator (15℃). 2. The pollens of these grafted plants seemed to have a tendency of being a little smaller in size than those of the mother plants, but with regard to the fertilty, i. e. the percentage of well-stained pollen grains with aceto-carmine, both showed similar good results. 3. Germination tests of these pollens were undertaken by using sucrose-agar medium and hanging drop (sucrose sol.). Generally the agar culture seemed to be better for germination, while for the pollen tube growth the hanging drop culture seemed to be better. 4. It was noticed in many cases that the pollen from the plants grafted on P. Thunbergii showed germination and pollen tube growth slightly better than that of the scion mother plants, while the pollen of the plants on P. densiflora showed growth a little worse than that of the mother trees. 5. As to the differences in germination and pollen tube growth between the pollens of the grafted and mother plants, it seemed to be difficult to find a uniform tendency or regularity: in grafted P. Pinaster the germination percentage was considerably lower than in the case of the non-grafted plants, while in the tube growth no clear difference could be seen; grafted P. strobus and P. excelsa on P. Thunbergii showed somewhat better results on the germination and pollen tube growth than their mother plants, whereas the reversed relation was recognized in the case of P. Banksiana. However, these differences between the two kinds of pollens do not seem to be so conspicuous. In general, the pollen of the grafted plants could show as good a germination percentage and pollen tube growth as the pollen of their mother plants. 6. The results mentioned above led to the conclusion that the pollen from the grafted pine plants have a possibility to be used for breeding. 7. Some differences could be seen in the pollen of the young non-grafted plants (5 years old) of P. densiflora or of P. Thunbergii, when compared with the pollen of the matured trees of the same kind (ca. 30 years old); the size was a little smaller (signficant at 1% level), and the germination percentage as well as the pollen tube length were lower in the former, therefore, it is conceivable that matured trees rather than young trees should be used for scions.