Artificial light and growth regulators on the in vitro etiolation of Cattleya labiata

ABSTRACT The technique of etiolation is widely used in the micropropagation of various plant species. The aim of this study was to evaluate growth and development in shoots of Cattleya labiata grown in vitro, as a function of growth regulators and the presence and absence of light. Stem segments, approximately ± 1.0 cm in height, were inoculated in test tubes containing 15.0 mL of MS culture medium supplemented with different concentrations of BAP (0.0, 2.0 and 4.0 mg L-1) and NAA (0.0, 1.0 and 2.0 mg L-1), and in different growth environments (growth room, darkness and a photoperiod of 16 hours) in a completely randomised design. At 150 days, the following were evaluated: a) number of etiolated shoots; b) number of nodes per etiolated shoot; c) length of stem segment (cm); d) number of roots; and e) total seedling dry weight (g). The highest mean values were achieved with the use of 4.0 mg L-1 BAP and 1.0 mg L-1 NAA for the number of etiolated shoots, and 2.0 mg L-1 NAA for the number of nodes per etiolated shoot in the absence of light. The length of stem segment was greater in the absence of light; in contrast, the number of roots and the total seedling dry weight were greater in a bright environment, irrespective of the growth regulator added to the culture medium. The etiolation of stem segments is a viable technique, as it provides features that are advantageous in the in vitro multiplication stage of the species.

摘要 黄化技术广泛应用于多种植物的离体微繁殖中。本研究旨在探究生长调节剂及光照条件对离体培养的唇瓣卡特兰（Cattleya labiata）芽生长发育的影响。本实验将高度约1.0 cm的茎段接种于含15.0 mL MS培养基的试管中，培养基添加不同浓度的6-苄氨基腺嘌呤（BAP，0.0、2.0和4.0 mg·L⁻¹）与α-萘乙酸（NAA，0.0、1.0和2.0 mg·L⁻¹），并设置三种培养环境（培养室、全黑暗、16小时光周期），采用完全随机设计。培养150天后，对以下指标进行测定：a）黄化芽数量；b）单黄化芽的节数；c）茎段长度（cm）；d）根数；e）幼苗总干重（g）。在全黑暗条件下，添加4.0 mg·L⁻¹ BAP与1.0 mg·L⁻¹ NAA时黄化芽数量达到最高均值；添加2.0 mg·L⁻¹ NAA时单黄化芽节数达到最高均值。全黑暗环境下茎段长度更长；相反，无论培养基添加何种生长调节剂，光照环境下的根数与幼苗总干重均更高。茎段黄化技术是一种可行的离体繁殖手段，可为该物种的离体扩繁阶段提供有利条件。