文心蘭Gower Ramsey生長與氮素分配之周期變化與季節對其花序品質之影響

Cyclic Change of Growth and Nitrogen Partitioning in Oncidium Gower Ramsey and Effect of Season on Inflorescence Quality

文心蘭目前是臺灣第二大的蘭花作物，切花產量多集中於4-6月及9-10月，其中又以4-6月之切花品質較佳。瞭解植株生長量變化及氮素在植體內之分配對於植物的生長發育可提供許多資訊，而文心蘭在這一方面的研究相對有限。本研究之目的係為瞭解文心蘭Gower Ramsey在一完整生長周期內乾物重與氮素之變化與在植體內之分配情形，並以此觀點來探討季節對栽植於北台灣文心蘭的切花品質之影響。在文心蘭新芽發育階段，新根生長旺盛，植株累積乾物質。在進入假球莖出鞘期前，文心蘭會先經歷芽體分化與假球莖形成，此階段根部及前代莖葉之乾重及氮含量下降，待假球莖出鞘再繼續累積養分。在花序發育階段，植株內各器官均持續累積乾物質及氮素，達單一生長周期之最高點。隨著花序開放，除花序外植株其餘部位的養分含量皆出現下降的情形，顯示花序的開放大量耗用植株所貯存之養分。隨著新一代芽體之發育，當代假球莖會出現再充實之現象，而前代假球莖對於養分的積貯能力則相對較弱。比較各季節之植株生長量顯示，6月與3月採收切花之文心蘭，當代假球莖所含之乾物質較高，花序品質較佳；9月採收切花之文心蘭，當代假球莖內的氮濃度較高，葉片生長旺盛，唯乾物量累積不足，花序品質不佳；而12月採收切花之文心蘭，當代假球莖及葉片之生長量最差，花序品質最低。隨著季節、環境光度與溫度改變，文心蘭對養分之蓄積能力產生變化，進而影響植體對乾物質及氮素的分配，使得9月與12月份之植株切花品質低於6月與3月份所生產之切花。 Oncidium ranks as the second largest orchid crop in Taiwan. Its cut flower production peaks from April to June and September to October, and the inflorescence quality is better from April to June. The patterns of dry matter and nitrogen partitioning offer useful information for understanding the plant growth and development in Oncidium. We thus investigated changes of dry matter and nitrogen content of various plant parts in Oncidium Gower Ramsey grown in northern Taiwan during a growth cycle, to know how seasonal changes affect the inflorescence quality. In bud and plantlet stages, Oncidium Gower Ramsey grew new roots and accumulated dry matter. Prior to unsheathing stage, bud differentiation and pseudobulb formation consumed the nutrients that accumulated in roots and back shoots; thereafter, the plant continued to accumulate nutrients during pseudobulb development. During inflorescence development and branching, dry matters and contents of nitrogen in Oncidium kept increasing in all organs; the dry matter and nitrogen content in the whole plant reached their maximum points. Upon flowering, nutrients in plant organs decreased except in the inflorescence, indicating that great amounts of stored nutrients were consumed during this stage. When new shoot was developing from the current shoot, the current pseudobulb again accumulated nutrients, but the capacity of nutrient accumulation in back pseudobulbs was lower compared with the current pseudobulb. Oncidium, bearing inflorescence in June and March, had more dry matter partitioned to current pseudobulb than in other months, resulting in better inflorescence quality. Plants with inflorescence harvested in September had higher nitrogen concentration in current pseudobulb with more vigorous leaves, whereas the accumulation of dry matter in current pseudobulb was less than those in other months; the flowering quality was fair. Oncidium with inflorescence harvested in December had the lowest dry weight for both current pseudobulb and current leaves than those in other months, resulting in the worst inflorescence quality. Light intensity and temperature changed with season, and both environmental factors affected the partitioning of dry matter and nitrogen in Oncidium. Therefore, the quality of inflorescence harvested in September and December was worse than those harvested in March and June in northern Taiwan.