Effects of different forms of nitrogen sources in the culture media on the growth of Cattleya young seedlings (Department of Agriculture)

Cattleya (Lc. princecs margaret×Lc. bonnanza giant)の初期幼苗を材料にして2段階のステージ(発根前と発根後)について窒素肥料の形態と濃度の影響を調査した。窒素の形態としてはNH_4,NO_3,NH_4+NO_3,尿素の3形態4区としそれぞれ50∿400ppmの窒素濃度について調べた。1.発根前の苗に対してはNH_4は低濃度区のみで良好な生育を示したがNO_3区では全濃度区を通してほぼ同様の生育を示した。最も良い結果はNH_4+NO_3の窒素区で得られた。尿素は低濃度区ではかなりの生育を示したが高濃度区は不適であった。2.NH_4+NO_3区は発根後の幼苗の生育に対しても最もよい結果を示した。このステージの苗はNO_3および尿素の高濃度区に対してもかなりの生育を示した。NH_4の高濃度区に対しては苗令IIの苗においても生育は殆ど改善されなかった。3.発根後の苗に対してはNH_4とNO_3が同時に培地に含まれておれば800ppmの高濃度区でも生育に支障はなかった。4.同一培地の中におけるNH_4とNO_3の割合についてはNO_37∿8に対してNH_42∿3の割合が適当であった。5.苗令が進展するにつれて窒素の形態や濃度に対する利用可能な範囲が広くなることが確かめられた。Attempts to make clear the effect of forms and concentrations of nitrogenous nutrients on the growth responses of orchid, Cattleya (Lc. princess margaret x Lc. bonanza giant) seedlings, at their not yet rooted (age I) and rooting (age II) stages, respectively, were made using the aseptic culture techniqus. As the sources of nitrogen, NH_4,NO_3,NH_4+NO_3,and urea forms were used, their nitrogen concentrations ranging between 50∿400ppm. 1. When grown in the medium containing NH_4 as the only source of nitrogen, age I seedlings showed always a quite normal growing within the lower concentrations, but with the higher concentrations they resulted in more or less inhibited growth throughout all the concentrations tested. The best growth response was detected when age I seedlings were grown in the medium containing both NH_4 and NO_3 as nitrogen sources. In the urea and NO_3 media age I seedlings showed similar responses as in the NH_4 medium. 2. In the medium containg both NH_4 and NO_3 the seedlings at age II (rooting stage) showed fairly excellent growth throughout all the concentrations tested, and moreover, such seedlings did not show any restriction in their growing in the media containing higher concentrations of NO_3 or of urea nitrogen. In the medium having higher concentration of NH_4 those seedlings (age II) not showed, any improvement of their growing as compared to the seedlings at age I stage (not yet rooted). 3. When grown in the medium containing both NH_4 and NO_3 forms as the sources of nitrogen, age II seedlings showed quite normal growth even at higher concentrations up to 800ppm, that is 4 times of the standard, not accompanying any cessation of their growth at all. 4. The most favorable growth of seedlings were observed in the media having both NH_4 and NO_3 forms, their preferable mixing composition being 20∿30% of the former and 80∿70% of the latter. 5. With the progress of growing stages of seedlings the favorable utilization ranges of nitrogen sources became to be quite extended in their chemical compositions and concentrations