改變積儲影響番木瓜營養與生殖生長

Abstract

番木瓜(Carrica papaya L.)為台灣中南部普遍種植之重要經濟果樹，並以栽培‘台農二號’兩性株為主。番木瓜兩性株容易產生花性變異，造成畸形果或於連續節位產生雌蕊退化型花，造成番木瓜結果不連續現象，此現象在台灣通常稱之為著果斷節（fruit set failure）。番木瓜兩性花花性變異程度依遺傳、植株所處環境與植株生理狀況而有差異，由其以植株生理狀況為影響變異程度之主要因素。番木瓜植株斷節問題和積儲與供源比例(sink-source ratio)相關，本研究在調節積儲以調節營養生長與生殖生長達成產量的穩定，與不影響果實品質。 試驗地點在高雄市六龜區之台農二號番木瓜網室，株齡13個月的兩相鄰果園，番木瓜植株於連續50節之著果後，易產生約20節之斷節，且著果斷節問題在田間為普遍發生。再藉疏果調節供源與積儲關係以改善番木瓜斷節問題；疏果處理自始果節位算起連續處理50節，以三葉節為一處理單位，依疏果程度分成全部不留果、三節留一果、三節留兩果、一節留一果，並以不疏果為對照組；疏果處理植株的每節開花數依疏果程度增加而提高，每節平均正常兩性花數與側芽數也顯著提高；對照組每株約有10節的斷節，處理組則無斷節產生。疏果處理可使植株有較多同化物用於新生花芽與營養器官之生長，顯示番木瓜以疏果處理可改善供源與積儲關係，減輕番木瓜著果斷節問題。 第二部份之試驗以疏花改變番木瓜之積儲，並探討其對植株營養與生殖生長之影響。疏花處理分為五種程度，分別為對照組(CK)、疏軸頂花(RTF)、只留軸頂花(TF)、留軸頂花與第一分枝花(TF1F)與留軸頂花與第二分枝花(TF2F)。對照組與RTF處理的兩性花花數在前期多，但於六、七月時減少；TF之兩性花數較少，TF1F與TF2F則兩性花數皆維持在1-2朵，相對之下TF1F與TF2F處理之兩性花花數較穩定，並可持續以一節1-2果方式穩定著果。 植株處理節位內之掛果數會影響後期新生節位果實數量，對照組、疏軸頂花(RTF)之掛果數集中在前50節，TF、TF1F及TF2F處理50節內果數較少，但50節後仍能持續著果；處理節掛果數較多之對照組與RTF植株產生約20-25節之斷節，TF處理幾乎無斷節，TF1F與TF2F處理則斷節數少於20節，斷節數較少植株可提早回復著果，對產量中斷影響較小。疏果處理影響植株莖部與葉部生長，掛果數較多之對照組與疏軸頂花(RTF)處理之株高與莖粗生長量皆顯著較低；葉數與葉面積較低、第13葉節至頂芽長度也較短。對照組與RTF處理之果實較小，單株產量也較低，植株對逆境抗性也較低，在試驗結束時死亡率偏高。疏花處理可影響植株積儲與供源之比例，造成植株營養與生殖雙方面之影響，經疏花之TF1F與TF2F處理不僅斷節問題較輕微，更能提供較穩定且較高之產量，並能維持較對照組高之存活率。TF2F處理之植株營養狀態與產量表現均較其它處理好，為較適宜之疏花操作方式。

Floral sex variation of papaya (Carica papaya L.) is quite often happened on hermaphrodite papaya trees. It causes discontinuously fruit setting and results yields instability and the reduction of yield. The degree of the flower sexual change is dependent upon papaya variety, environment and the interaction of both effects on plant physiology. In the field studies, we examined the possibilities to decrease discontinuously fruit setting by different degree thinning fruits and flowers to affect the vegetative and generative growth of hermaphrodite papayas of ‘Tainung No.2’ cultivar. Papaya planted in net house at Liugui district, Kaohsiung city, which has been grown 13-month-old. Fruit setting failure often occurred after trees having setting 50 fruit nodes, and there were happening 20 nodes without fruit set. Fruit thinning is used to manipulate the source-sink ratio, less sink competition might provide more resource to supply fruit setting and flowering, eventually. Five levels of fruit thinning treatment were practiced including the control, all fruit removal, one, two and three fruits left on every three nodes, respectively. The experiment continually treated with 50 nodes from the beginning fruit setting node. Fruit thinning treatments were significantly effect on decreasing the degree of discontinuous fruit setting; and elongata flower numbers was more dependent on the fruit thinning. Five defloration treatments were practiced on ‘Tainung No.2’papaya trees. It significantly affected numbers of papaya hermaphrodite flower sexual expression, stem growth and leaf numbers, fruit setting distribution on stem, stress adaptation. The fruits on treatment of removal terminal fruit, and control that have much more fruit load at earlier fruit set period, having more discontinuously fruit setting nodes, and were affected plant survival rate and cause yield loss in the study. However, the removal 1st or 2st peduncle flowers and remain terminal flower of main axial promote papaya trees more yield and longevity.