VEGETATIVE RESCUE AND ROOTING OF CUTTINGS OF DIFFERENT STOCK PLANTS OF Sequoia sempervirens

ABSTRACT Sequoia is a fast-growing, long-living species, producing durable timber. The aim of this study was to test different methods for the vegetative rescue of Sequoia sempervirens trees over 40 years old, made at different periods of the year, and, later, testing the rooting of individualized cuttings in planned arrays. Twenty-four individual sequoias were rescued, applying girdling and semi-girdling at three different heights (-10, 0, and 30 cm). The first collection was made 90 days after application of the treatments, being repeated at 150, 240, and 360 days. The percentage of budding trees and the number of shoots per array were registered. In all collections, shoots produced cuttings, which were placed for rooting in mini-tunnels. Cutting survival (%), rooting (%), and number of roots were registered, per array, and per collection. The species vegetative rescue proved to be efficient for the production of shoots for stem cuttings, especially with girdling at 30 cm and semi-girdling at -10 cm. However, it is difficult to define the best method, mainly because of the genetic effect among stock plants. The rooting of cuttings, of recovered material, presented good results (average >65%), also with great differences among stock plants. The potential for rooting of cuttings varied according to different planting periods, with high rooting rates in all seasons, especially in summer. Sequoia sempervirens shows the potential for vegetative rescue and cloning by rooting of cuttings, and this may lead to new studies, with a view towards fixing clones.

摘要：红杉是一类生长迅速、寿命悠长的树种，其木材质地坚韧耐用。
本研究旨在针对树龄超40年的北美红杉（Sequoia sempervirens），测试不同时节开展的无性救护（vegetative rescue）方法，并后续在规划设置的扦插单元中检测单株插穗的生根情况。
本研究共对24株北美红杉实施无性救护处理，分别在-10 cm、0 cm、30 cm三个高度施加环剥（girdling）与半环剥（semi-girdling）操作。首次采样于处理后90天开展，后续分别于150天、240天、360天进行重复采样。研究记录了萌动植株百分比及每个扦插单元的萌条总数。
各批次采样获取的萌条均被制备为插穗，放置于微型扦插拱棚（mini-tunnels）内进行生根培养。本研究同时针对每个扦插单元及每批采样，记录了插穗成活率（%）、生根率（%）及单穗生根数。
结果表明，该树种的无性救护技术可高效获取茎插所需萌条，其中以30 cm高度环剥与-10 cm高度半环剥处理效果尤为突出。但由于母株（stock plants）间存在遗传效应差异，难以确定统一的最优处理方法。
救护获取的插穗材料生根表现优异，平均生根率＞65%，且不同母株的插穗生根效果仍存在显著差异。插穗生根潜力随扦插时段不同而波动，各季节均表现出较高生根率，尤以夏季表现最佳。
北美红杉具备通过无性救护及插穗生根实现克隆繁殖的潜力，该研究可为后续优良无性系的固定及相关拓展研究提供理论参考。