抄録
関東地方に生育するコナラ88個体の果実(堅果と殻斗)を2001,2002年に採集し,各果実形態について計測した12形質と,採集地点の環境要因(標高,暖かさの指数,年平均気温,降水量)との関係を調べた.堅果の全形質と殻斗の3形質,殻斗の柄の1形質は,標高および果実成長期間降水量との間に有意な負の相関を,暖かさの指数および年平均気温との間に有意な正の相関を示した.したがって,降水量が多くWI値が低い地域では,堅果,殻斗,殻斗の柄の形態が小さくなることが明らかになった.この果実形態にみられる傾向は,採集地点間での果実成長期間長の相違によるものであると考察した・コナラの果実形態を示す形質は,果実成長期の中でも成長期後期の降水量と有意な負の相関関係を示した.したがって,コナラの果実形態は,果実成長期後半の少降水量と強く関係することが明らかになった.しかし本研究では,果実形態に対する温度,降水量の影響を分離して解析することはできなかった.さらに,コナラの堅果長は堅果幅と比べて,温度条件に対してより高い依存性を持つことが明らかとなった・堅果長の温度条件への高い依存性は,8月以降堅果幅の成長が頭打ちになるのに対して,堅果長は8月以降にも成長を続けるという,発達パターンの違いによるものと考察した.
Acorns (nuts and cupules) of 88 Quercus serrata Thunb. individuals in central Japan were collected in 2000 and 2001, and the relationships between twelve acorn traits and several environmental factors, such as altitude, warmth index (WI), annual mean temperature and precipitation were examined. All nut traits, three cupule traits and a peduncle trait were correlated negatively with altitude and precipitation during the acorn growing season, and positively with WI and annual mean temperature. These results indicated that the higher the precipitation was and the lower the WI, the smaller were the size and volume of nuts and cupules. This suggests that the differences in the length of the acorn growing season among the sampling sites may be responsible for the trends in acorn size and volume. The acorn size traits of Q. serrata were negatively correlated with precipitation during the acorn growing season, especially within the latter part of the growing season. Thus, we conclude that acorn size of Q. serrata had some strong relationship to less precipitation in the latter part of the acorn growing season. However, it was difficult to separate the effects of precipitation from those of temperature on acorn traits in our analysis. Moreover, Q. serrata nut length was more dependent on thermal conditions than was nut width. This difference may be caused by the different developmental patterns between these two dimensions, especially after August when the width stopped increasing but the length did not.
