マツ属の葉の寿命

Abstract

マツ属各種が獲得した性質を理解するための一連の研究として、マツ属のもつ葉の寿命を冬季の着葉年数によって調べた。その結果, 下記の点が明らかにされた。1) 枝間の平均着葉年数は種類によって様々で, 1. 19-3. 53年程度であった。カラマツ属を除くマツ科植物内では, マツ属の葉の平均寿命は短い値をもっていた。2) マツ属各種のもつ様々な平均着葉年数と原産地の温度, 日長など, 特定の要因との関係は明かな対応関係になく, 葉の寿命がそれらに直接対応した性質ではないことを示した。3) 古い形質のマツでは, 着葉年数が長い種類が多い傾向が認められ, 時代の経過とともに葉の寿命の短い種類が分化したものと考えられた。4) マツ属での葉の寿命の長さは, 系統的な分類群間で異なる傾向と, 分類群内の近縁種間でも差異のある性質が明かになった。各系統, 各種間での差異は, マツ属が種によって独自の方向へと種分化した結果と考えられた。

In relation to speciation in the genus Pinus, leaf life span of 46 pine species and mean maximum leaf age in 60 species was examined, which had been planted under natunal condition at Kyoto. The leaf life spans were calculated from the monthly data of leaf fall rate as reported in the former study. The maximum leaf ages at the lower branch were measured in winter and shown in Table 1. The leaf ages or leaf life spans of pines are low to compare those of evergreen coniferous species. Although leaf ages are largely different among pine species from 1.2 to 3.5 years, the values had fundamentally no relation to the gradient of environmental conditions such as Mean Warmth Index or mean latitude at their native habitat as shown in Figs. 3 and 4. The difference in age of the species seemed to relate to the pine groups of taxonomy as the sample of Subsect. Gerardianae. On the other hand, the large difference of them appeared among pine groups of Subsect. Sylvestres or Subsect. Oocarpae. Many species of long life span are pines to have old features in the form of corns. Pines in old era are considered to be long life span. Present pines of short life span seemed to be formed by differentiation from the pines of long life span.