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Characteristics of leaf morphology and water relations were examined and compared for the leaves of Eucnlyptus grobulus which shows continuous changes of leaf form from oval in the current sprouts to ...lanceolate in the normally grown shoots. With the changes of leaf form, several anatomical features were observed to change continuously. The normal leaves had long petioles and showed some 'sun leaf' characteristics, i. e., three or four layers of mesophyll palisade cells, small specific leaf area, dense venation, and low air space ratio. On the other hand, the current sprout leaves showed the 'shade leaf' characteristics. On the abaxial surface of the current sprout leaves, smaller stomata in high frequency compared to those of normal leaves were observed. No stomata was observed on the adaxial surface of the sprouts leaves although there was about a frequency of 60% of abaxial stomata in the normal leaves. Water relation parameters obtained by the pressure-volume curve technique suggested that the sprout leaves were inferior in maintaining cell turgor against water loss compared to the normal leaves. Under field conditions, transpiration rates and stomatal conductances were higher in the sprout leaves, while leaf water potentials were almost the same in both the sprout and the normal leaves. The leaf specific conductance of tree bole supporting unit leaf area, calculated from the relationship between leaf water potentials and transpiration rates, was higher in sprouts. It was concluded that the sprout leaves, which have a lower-light efficient morphology and a smaller content of osmotic water, maintain the high stomatal conductance supported by a high leaf specific conductance.
ユーカリノキ（Eucalyptus grobulus）では当年生萌芽枝の薬は広楕円形であるのに対し，通常枝の普通策は披針形である．1年生萌芽枝の葉は基部から梢端へ向かって卵形から拡針形へと連続的に変化している．これらの葉について，形態および水分生理的特性の比較を行った．葉形の変化にともない葉の内・外部形態は連続的に変化していた．普通葉は長い葉柄を持ち，SLAが小さく，葉脈が密で，細胞間隙が比絞的少なく，3～4層の柵状組織を有しており，全体的に強光利用型の特性を示した．これに対して当年生萌芽葉は逆の特性を示し，弱光利用型であると考えられた．萌芽葉の気孔は普通葉と顕著に異なり，背軸側では普通葉より小型の気孔を多数つける傾向がみられたが，向軸側では気孔がほとんど観察されず，萌芽により，片面気孔化する傾向が認められた．また，葉の水分特性をP－Ⅴ曲線法で求めた結果，萌芽葉は葉の水分損失に対する気孔開度の維持機構が普通葉に比較して劣ることが推察された．自然状態で測定された蒸散速度および気孔コンダクタンスは，萌芽葉で非常に大きな値を示したが，葉の水ポテンシャルの日変化では，両者に大きな差はみられなかった．これらの野外測定データから計算された単位葉面積を支持する器官の水分通導性は，普通枝よりも萌芽枝で高かった．したがって，弱光利用型の形態を持ち，相対シンプラスト水量の少ない萌芽葉では，水分通導性が高く葉への水分供給が容易なことが，高い気孔コンダクタンスを維持する大きな要因となっていると考えられた．show more
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