||The branching characteristics of Q. acwtissima and Q. serrata seedlings grown for four years under shade and under full sunlight were compared to determine the plasticity of the crown architecture to ...low Relative Light Intensity (RLI) and additional inorganic fertilizer. The primary branching pattern reflected the phyllotaxy of both species, specifically, branches originated from lateral buds on every leaf on the rossette of 4 to 5 leaves at the end of a stem in Q. serrata and rrom any of the spiral of 4 to 12 leaves from a single stem in Q, acutissima, The bifurcation ratio was lower and more constant in Q. sewata (5.7), than in Q. acutssima (8.5). Based on previous findings that bifurcation ratio is inversely proportional to shade tolerance, a lower bifurcation ratio in Q, serrata may indicate greater shade tolerance. The difference in the degree of variability in the bifurcation ratio between the two species may be due to the constancy in the branching pattern of Q, serrata and the less determistic branching in Q. acutissima. In Q. serrata, the rossette branching pattern and the number of branches produced from an existing growth module remained mostly the same under any condition. On the other hand, branches in Q. aculissima did not originate from every leaf on the stem, instead, branches were produced from any of these leaves, providing more variability in the degree and pattern of branching. In Q. serrala the mean branch length under shade was significantly (p<0.0001) longer than those of seedlings grown under full sunlight with no fertilizer and with 10 g of fertilizer, Compared to seedlings grown under full sunlight with 10 g of fertilizer, the mean branch length of Q. acutissi~na seedlings was longer under Low RLI but was shorter under Very Low RLI. Although not statistically significant, Heavy Fertilizer and Low RLI treatments decreased the mean branch angle in Q. serrata, while Heavy Fertilizer treatment slightly increased the mean branch angle in Q. acutissima. The mean interbranch length of Q. sewata and Q. acutissima seedlings grown under shadc were longer than tliose of seedlings grown under lull sunlight. However, this was significant (p<.0001) only between seedlings in the control (no fertilizer) and those under Low RLI. Variation in the branching characteristics such as the bifurcation ratio, the branch length, interbranch length observed in seedlings under shadc and additional fertilizer were species specific. This may be duc to the strong influence of leaf phyllotaxy on each species' branching pattern.
ブナ料コナラ属クヌギ（Quercus acutissima）とコナラ（Quercus serrata）の分枝形態の可塑性を明らかにするために庇陰処理と施肥処理を行い，分枝形態の変化について研究した．両種の分枝形態は葉序の様式を反映しており，コナラは茎の先端にロゼット状に配置された葉の葉腋から車輪状に側枝を出し，クヌギは茎上に配置された輩の葉腋から側枝を螺旋状に出した．分枝比はコナラで5．7，クヌギで8．5の範囲で変化し，コナラの反応が小さかった．つまり，環境の変化に対しコナラは車輪状の発生様式を変化させず，しかも側枝数をほぼ一定に保つのに対し，クヌギは側枝の発生する葉腋数を変化させて対応した．これまでの報告例から分枝比の小さいコナラの方が耐陰性の強い種と考えられた．平均枝長はコナラでは庇陰下で全光下よりも有意に長く，クヌギでは弱い庇陰では長く強い庇陰では短かった．枝の岐出角はコナラでは有意ではないが多施肥と弱い庇陰で小さくなり，クヌギでは多施肥でわずかながら大きくなった．枝間長は両樹種ともに全光よりも庇陰で長くなる傾向が認められた．これらの分岐係数，枝長および枝間長などの枝特性は種に特有であり，特に葉序の影響を強く受けていると考えられた．続きを見る