The Effect of Bending on the Wind Tolerance of Papaya

Abstract

Owing to the Papaya's characteristics, high and hallow trunk, slenderly leaf petiole succulent root, soft stem tissue, it's susceptible to nature windy disaster. Injury will usually occur when wind grade is over 7 (≧ 13.9-17.1 m/sec). Basal trunk bending of Papaya c.v. Tainung No.2 result in length of internode, number of leaf, and trunk cavity decrease. Significant effect of higher survival rate and lower damage rate was obtained after Typhoon Herb on July,1996 in Taiwan. 2 months after of bending treatment, tissues were observed to have increase cell density, decrease pith cavity, and scatter irregular secondary phloem. Firmness of stem flesh and trunk also increased on mechanical characteristics. Trunk volume and density increased, trunk cavity decreased on physics study. Survival rate, stem damage rate , stem damage rate, papaya growing duration, and net house using efficiency of bending treatment were also obviously being improved. Therefore, bending culture on paapya is obviously a more efficient cultivation methods than traditional one.番木瓜因屬熱帶果樹，幹高葉大莖幹具有空腔，葉柄細長，根為肉質根，莖幹組織柔弱，對天然災害抵抗力較弱。一般風速在七級(即13.9~17.1公尺/秒)以上則造成風害，本研究以台農二號番木瓜(Tai-nung No.2)為主要研究材料，將其莖幹基部偃曲，偃曲後株高矮化，節間縮短，葉片數減少，當1996年7月31日賀伯颱風(最大風速25m/s)侵襲後，偃曲栽培受害程度最低只有2.8％倒伏率，對照達76.2％。不同節位之位置機械性質測定，偃曲後莖肉硬度、莖幹硬度較對照組低，衝擊強度反而增加，物理測定偃曲處理後實驗莖幹體積增加，中心空腔體積明顯減少，莖幹密度明顯增加。偃曲處理對風害防治有明顯改善，在莖幹折損、整株倒伏率極低