マツ属の球果の発達

Abstract

京都大学農学部附属演習林上賀茂試験地に導入育成された外国産マツ属の生殖器官の発達を調べるため, 本報告では20数年経過したマツ属19種類を対象として, それぞれの種類の球果の発達過程について比較検討した。なお, 本調査は1951年から1952年にわたって調べられたものである。その結果は次のとおりである。1) 球果の生長開始期は種類の違いに関係なく, 3月上旬の日平均気温がほぼ5℃になる頃に一斉に始まった。2) 球果の生長終了期は種類によってそれぞれ異なり, 暖かい地域を原産とする種類では球果の生長終了が遅い時期 (7月下旬) に, 寒い地域を原産とする種類では早い時期 (6月上旬) に訪ずれ, 種類間では8週間もの差がみとめられた。3) 球果の初期生長速度は暖かい地域を原産とする種類で小さく, 寒い地域を原産とする種類で大きい傾向がみられた。また, 球果の生長速度の変化の違いによって大きく2つのパターン分けがみとめられた。それらは当試験地よりも暖かい地域に原産地をもつ種類と寒い地域に原産地をもつ種類との違いと対応していた。4) クロマツで調べられた球果の生長終了期と受精期はほぼ同時に起っていて, 他の種類でも両者の間に密接な関係があるものと推測された。この結果から, 暖かい地域を原産とする種類では受精期が遅れ, 逆に寒い地域を原産とする種類では早い時期に受精するものと予測された。

In order to make clear the developmental process of sexual organ of pines, this paper discusses the cone growth in volume on three Japanese pines and on 16 exotic pine species which were brought up for over 20 years after introduced to Kamigamo Experimental Forest Station of Kyoto University. The investigations were carried out in the definite intervals of 2-weeks during the growing season in 1971 and 1972. The results obtained were as follows; 1) When daily mean temperature has reached upward of 5℃ at early March, the cone growth of all pine species simultaneously began to start unrelated with species (Table 1 and Fig. 5). 2) The date of completion of cone growth was different in each pine species. In general, the completion of the volume growth in pine species from mild climate region was late (late July), but early in the species from cool climate region (early June). The difference of about 8 weeks has been recognized between the former and the later (Table 1 and Fig. 5). 3) In the early stage of 2nd-year cones, the growth rates of cone were slower in pines from mild climate regions, and were faster in species from cool climate regions. The pattern of seasonal changes of cone growth rate was divided into two groups of species. One is the species introduced from warmer regions than Kamigamo Station, and the other is the species from cooler regions (Fig. 8). 4) The date of completion of cone growth and the date of fertilization in Pinus thunbergii seems to happen at same time, and it is supposed that there may be a close relation in both times of the other pine species as well as recognized in P. thunbergii. Consequently, the time of fertilization must be late in pine species from mild climate region, and early in pines from cool climate region.