疏花對臺農二號番木瓜營養與生殖生長之影響

Effects of Defloration on Vegetative and Generative Growth in Papaya 'Tainung No. 2'

番木瓜（Carica papaya L.）在臺灣以栽培‘臺農二號’兩性株為主。番木瓜兩性株容易產生花性變異，造成著果不穩定而影響產量，而植株供源與積儲之比例會影響花性變異。本試驗於屏東縣長治鄉高雄區農業改良場進行，植株於定植5個月後進行五種疏花處理，分為對照組、疏軸頂花（removal of terminal flower，RTF）、只留軸頂花（removal of all flowers except the terminal flower，TF）、留軸頂花與第一分枝花（removal of all flowers except the terminal flower and first peduncle flower，TF1F）以及留軸頂花與第二分枝花（removal of all flowers except the terminal flower and secondpeduncle flower，TF2F）。調查植株之開花數、花性、果實數與斷節（fruit set interruption）情形、果實品質與產量，以及株高、幹徑、葉面積、葉數與葉片光合作用速率。結果顯示對照組及RTF處理在六及七月兩性花數銳減，TF1F與TF2F處理則三到六月每節位皆能維持1－2朵正常兩性花，到七月才下降，但仍高於對照組及RTF處理。對照組與RTF在試驗結束時死亡率偏高，進而減少產量，TF1F與TF2F處理單株產量分別高於對照組24%、36%，且能維持較對照組高之存活率。處理中以TF2F之植株總體表現較其他處理好，為較適宜之疏花操作方式。 Hermaphroditic 'Tainung No. 2' papaya (Carica papaya L.) has been the main cultivar for papaya production in Taiwan. However, fluctuation in flower sex has been common in hermaphroditic papaya and often leads to inconsistency in crop load and market supply. Source/sink ratio could affect flower sexual variation. In this study, five defloration treatments to manipulate source/sink ratio were tested: 1) plants without defloration as the control (CK), 2) removal of the terminal flower (RTF), 3) removal of all flowers except the terminal flower (TF), 4) removal of all flowers except the terminal flower and the first peduncle flower (TF1F), and 5) removal of all flowers but the terminal flower and the second peduncle flower (TF2F). Flower number, flower sexual, fruit number, fruit set interruption, fruit quality, and plant yield were recorded. Plant height, stem perimeter, leaf area, leaf number, and leaf gas exchange were also measured. Results showed that elongata flower number decreased in CK and RTF plants when measured in June and July. Elongata flower number maintained at 1 to 2 flowers per node in TF1F and TF2F treatments in June but decreased in July, but the number was still higher than CK and RTF treatment. Plant survival was lower in CK and RTF than other treatments, and it caused yield decrease. Individual plant yields in TF1F and TF2F were 24% and 36% higher than the control, respectively. TF2F had the best overall performance and was proposed to be a suitable defloration practice.