不同氮素型態對矮牽牛生長開花之影響

Effect of Various N-form on Growth and Flowering of Petunia hybrida Vilm. Cv. White Cascade

矮牽牛（Petunia hybrida Vilm. cv. Whie cascada）施以硝酸態氮、銨態氮、尿素態氮，行砂耕或混合土栽培。於春、秋、冬季間分別進行試驗。測量植株生長勢及開花情形，並取葉片分析其無機養份。NH4-N處理之植株在地上部、根部鮮重、花數、花壽命，均不及NO3-N與U-N處理者；且根部呈木栓狀而在葉部有黃化或壞疽等銨毒害現象發生。此銨毒害癥狀之發生，以初秋較冬季栽培時出現早；而土耕之NH4-N效應較不明顯。加入CaCO3後，可使NH4-N處理之植株生長勢獲得改善，但仍不及NO3-N或U-N者。NH4-N處理對K，Ca，Mg含量與NO3-N相較，分別相對地減少16，39及76%，故NH4-N處理劇烈地減少Mg含量；介質中拌入CaCO3後，可使NH4-N處理，葉片之K，Ca，Mg陽離子含量增加。本研究顯示，矮牽牛之氮肥宜採用尿素或硝酸態氮，忌用銨態氮肥，但土中拌入CaCO3卻可提高銨態氮肥之肥效。

Petunia (Petunin hybrida Vilm. cv. White Cascade) seedlings were grown with NO3-N, NH4-N, Urea-N(U-N) or NH4-N+CaCO3 under sand or soil mix culture. The experiments were conducted from autumn through spring of the next year. During the growing period, quantitative measurements of growth vigor and flowering were taken Leaves were analyzed for mineral composition. Fresh weight of shoot, root, and accumulated flower number, flower diameter, flower diameter, flower life in plant, were reduced under NH4-N nutrition, those of U-N were superior to NO3-N during winter slid spring. Roots and leaven showed ”NH4 toxicity” symptoms, such as darken, corky and stubby roots; necrosis and chlorosis in leaves. It was found that NH4 toxicity appeared earlier in the early autumn than in the winter and spring, and sand culture showed more severely than soil mix culture. Addition of CaCO3 alleviated the toxicity and improved growth of plants. However, growth did not equal that on exclusively NO3-N or U-N. According to data of leaf analysis, NH4-N nutrition decrease cations content in petunia. In comparison with NO3-N, petunia grown on NH4-N relatively decreased K, Ca and Mg content were 16, 69, 76% respectively.