幼年性及其在大樹移植上之應用

Juvenility and Its Application in Large-Tree-Transplant

植物在幼年生長期容易營養繁殖，是為幼年性。幼年性在植物體內呈錐形變化，愈靠近樹基部及下位枝幹其幼年性愈強。當植物生長及成熟化，它們發根及發芽的能力逐漸消失。可以利用復幼或再活化的方法，使其分生組織恢復部分幼年性。復幼方法主要透過有性繁殖，形成合子胚胎，恢復幼年性；再活化有三種路徑：一、系列式微體繁殖產生癒傷組織；二、植物離體組織做系列式扦插、嫁接、壓條；三、截幹、樹籬式強剪、矮林作業、創傷，產生莖頂分生組織或根原體，再長出不定芽或不定根。復幼或再活化後的樹木可以不同程度的增加發根率。大樹移植上，常利用創傷方法做移植前樹冠清理、斷根、老根環剝、削根球和在氣生根與樹幹上導出不定根等，以刺激幼年性組織長出足量不定根及不定芽，增加移植存活率。

"Plants in the juvenile phase of growth generally are easier to propagate vegetatively. Juvenility changes within plant body like a cone shape with the trunk base preserving its juvenility throughout the plant's life. The lower branches have more juvenility than the upper canopy. As plants grow and mature, their rooting and sprouting capability diminishes. Rejuvenation and reinvigoration can be adopted to restore juvenility for better rooting and sprouting performance. Rejuvenation usually undergoes meiosis to produce zygote embryos. Reinvigoration has three different pathways: A. serial micro-propagation or tissue culture to generate callus; B. serial cutting, grafting, or layering of explants to form SAM (shoot apical meristem); C. heading, hedging, coppicing, and wounding plants to initiate SAM or root primordium. The embryo, SAM, and root primordium will then form plant organs and the whole plants. On the large-tree-transplant, shoot pruning, root pruning, root girdling, rootball slicing, and adventitious roots induction are common methods in stimulating juvenile tissues to generate adventitious shoots and roots for the recovery of necessary physiological functions of trees and enhance the transplant success."