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ソルゴー(cv.ハイブリットソルゴー)を供試して, 刈取り時の貯蔵物質を実験的に操作し, 再生時の分げつ芽の伸長, 分げつ数の変化を調べ, 次の結果を明らかにした.1.鉢試験, および圃場試験によって, 刈取り時に芽数, 芽の高さをそろえた下で刈取り高さを変え, 再生を調べた.刈取り直後には刈取り高さの高い貯蔵物質量の多いもので分げつ芽の伸長が遅く, 刈取り高さの低いもので速やかである.しばらく経過すると両者の関係が逆転し, 貯蔵物質多のものは伸長量大となった.分げつ数では, 刈取り直後では前記の傾向は明瞭でなく, 後期では分げつ芽の伸長でみられた傾向と同様であった.刈取り前遮光処理を行なったものや刈取り時根を切断したものでは, それぞれのなかでの傾向は全く同様な結果を示したが, 刈取り直後の分げつ芽の伸長量は標準区に比べて同一貯蔵物質量でみると著しく低かった.2.芽の高さを変え, 芽数を揃えて, 再生を比較すると, 芽の高さの高いものが, 低いものに比べて, 刈取り直後において, 分げつ芽の伸長量が特に大であった.3.刈取り時に1%のIAAおよびIAA+GAのラノリンペーストを切口へ塗布したところ, 無処理<IAA<IAA+GAの順に再生が遅延することが見られ, またそれぞれの処理中の刈取り高さの差異による刈取り直後での上記した影響も相加的に認められた.なお貯蔵物質が少なく, IAA濃度の濃いと思われるものほど枯死株の発生が大であった.4.刈取り高さの異なる切株の地表面近くでの刈取り直後でのオーキシン量を調べ, 刈取り高さの高いものは低いものに比べて, その濃度が大であることを示した.5.以上の結果に基づき, 貯蔵養分の役割について見ると植物ホルモンの引金的働きの後, 貯蔵物質

Role of Organic Reserves upon Regrowth of Forage Plants. I. Elongation of Tiller Buds of Sorgo (Sorghum bicolor Moench) Plants after Cutting as Influenced by Levels of Organic Reserves. Hisakazu OIZUMI. Faculty of Horticulture, Chiba University, Matsudo, Japan. Tech. Bull. Fac. Hort. Chiba Univ., No.25: 55-62, 1977. Sorgo plants cultivated under pots or field conditions were cut at some different heights at the stage of booting or headtime to produce plants with different levels of organic reserves in stubble and roots. When cutting, the number of buds per plant and the height of the highest bud were equalized between cutting treatments by picking some buds. Regrowth (ratooning) of sorgo plants arises from the extension of leaf primordia from the meristems of tiller buds after cutting. The regrowth of plants just after cutting showed a marked negative correlation between the amount of organic reserves and growth of tiller buds. However, after a short duration, about 10-14 days after cutting, the relationship between them was reversed. In the case of the same cutting height with different position of buds, the regrowth of the plant with a bud at higher position was better than that at lower position. From these observations, phytohormone was thought to play an important role in regrowth. The lanolin paste of 1 percentage of IAA or IAA+GA was applied on the cutting surface of the stem. The elongation of buds was arrested by the treatments in the order of IAA+GA>IAA>Control. Endogenous auxin concentrations just after cutting at the stem base of the long or short cutting height were examined with the method of agar block diffusion technique and avena curvature test. The concentration of auxin was higher in the plants with high cutting height than in low cutting height. From these results, the role of organic reserves upon regrowth was found to become more clear after having taken the triggertic action of phytohormone upon buds.

source:The technical bulletin of Faculty of Horticulture, Chiba University