マダケの栄養要素含有率の季節的なうつりかわりについて

Abstract

無肥培のもとに生育しているマダケの葉, 稈および地下茎に含まれる養分要素である窒素, 燐酸, 加里, 石灰, 粗灰分の含有率と含水率を毎月1回づつ1年間にわたって定量し, これらの要素の季節的消長を調べた｡ その結果は第3表から第8表に, また第2図から第5図に示したが, これらについていえることは, 1. 各要素ともその季節的消長の特徴が, もっともよく表れるのは葉部であって, 稈, 地下茎部は加里以外の成分は比較的動きが少ない｡ 2. つぎに葉部の含有率をみると, まず窒素含有率 (乾物当り1.3 ~ 2.5%) は季節によって明らかに増減することを認めた｡ すなわち6月から10月の活動期には比較的低く, かつうごきが小さいが, 10月ごろから漸次増加し始めて翌年3月頃に最高となる｡ それ以後の4 ~ 5月の発筍期前には急激に低下していた｡ 燐酸含有率 (0.29 ~ 0.20%) は窒素の場合とややよく似た傾向を示すが, その増減の巾はきわめて少さい｡ 加里含有率 (1.7 ~ 0.2%) は前記2要素と異なり, 新葉開舒期に最高含量を示し, 以後翌年の葉がわり期まで明らかに低下していく傾向を示した｡ 石灰含有率 (0.2% ~ 0.7%) は加里の場合とは逆に, 新葉開舒期ならびにタケノコの伸長期に低く, 以後年間を通じて増加し, 蓄積していく傾向が認められた｡ 粗灰分は石灰含有率と同じように新葉開舒期ならびにタケノコの伸長期に低く, 以後翌年の葉がわり期までだんだん増加していく傾向がみられた｡ ただし粗灰分中の珪酸含量について調べた結果, 以上の傾向は主として珪酸の蓄積によるものであって, 灰分中の珪酸を除いた部分 (除珪酸灰分) は新葉開舒期, ならびにその交替期の間にあまり大差がみられない｡ 3. 含水率は葉部 (65 ~ 40%) は6月の新葉開舒期のころが最大であって, 以後徐々に低下して翌年の葉がわり期に最低となるのが認められた｡ 稈部, 地下茎部の増減の巾は比較的小さかった｡ 4. 以上の各要素はいずれも発筍期, タケノコの伸長期ならびに葉がわり期を軸として大きく移り変っていることが認められた｡

The present works were carried out to examine the seasonal changes of nutrient contents in Madake (Phyllostchys reticulata) in one year. The results of these determinations are given in Table 3--8, and Fig. 2--5. These indicate that; -- 1, It is in the leaf that all elements show the most distinct features of seasonal changes. 2, The contents in the leaf are as follows ; -- As to nitrogen contents (N. 1.3--2.5% on dry matter), it has distinctly varied with the season. That is, it was low in the sprouting season and the elongating term of rhizome (May--Oct.). Lates it increased gradually, and the contents reached the maximum in March of the following year. In April, before the sprouting season it decreased rapidly. P2O5 contents (0.21--0.28% on dry matter) wear little varied with the season. Seasonal changes of K2O contents (0.19--1.72% on dry matter) were different from those of the other. That is, the maximum contents were shown in the bearing season of new leaves (Jun.), and the contents gradually lowered until the falling season of leaves (Apr.) in the next year. On the contrary, CaO contents (0.23--0.77% on dry matter) were low in the bearing season of new leaves, and then increased until the falling season of leaves in the following year, but this range was comparatively narrow. Crude ash contents (8.85--16.00% on dry matter) were low in the bearing season of new leaves, and then increased until the falling season in the following year, but its increment seemed chiefly due to the accumulation of SiO2 in ash. Other elements except SiO2 in ash were nearly constant all the year round. 3, The water contents in the leaf (65--40% on fresh matter) reached the maximum in the bearing season of leaves (Jun.), and then gradually decreased to the minimum in the falling season of leaves in the following year. In the culm and rhizome, the range of seasonal changes was comparatively narrow.