变温对毛竹种子萌发及幼苗生长的影响

【目的】研究变温对毛竹(Phyllostachys edulis)种子萌发及幼苗生长发育的影响,了解竹类植物种子在不同温度处理下的萌发特性,以及幼苗1~5片叶展叶时的生长发育规律,为竹类植物实生苗研究提供理论依据和实践基础。【方法】采集广西桂林市灵川县大境乡的毛竹种子,在实验室培养箱中育苗,设定7个变温处理24 h内设置2个不同的昼夜温度(时长为12 h/12 h)组合 ]:29 ℃/15 ℃(T1),28 ℃/16 ℃(T2),27 ℃/17 ℃(T3),26 ℃/18 ℃(T4),25 ℃/19 ℃(T5),24 ℃/20 ℃(T6),23 ℃/21 ℃(T7)和1个恒温处理22 ℃/22 ℃(T8)。每隔12 h详细观测每个变温处理下每粒种子萌发时间、1~5片真叶展叶时间和叶下高,并测量叶片面积、地上部和地下部鲜(干)质量、根系形态、叶表面微形态、气孔长度和气孔密度。【结果】①在不同变温处理下,毛竹种子的萌发率均在50%以上;结合毛竹种子萌发的发芽势,发现T4—T7的种子发芽势高于30%;从T1—T8,毛竹种子的平均萌发时间逐渐缩短。②不同变温处理下的毛竹幼苗从第1片叶到第5片叶展叶时间逐渐延长;T6—T8处理下幼苗展叶时间和展叶数量都相对集中;同一培养处理下的毛竹幼苗从第1片叶至第5片叶的叶下高和展叶面积逐渐增加,温差越大毛竹幼苗叶下高越高;第3片叶后叶片的发育速率趋于稳定;温差越大,毛竹幼苗生物量也越大;根系在T3—T6处理下发育更好。③随着温差减小,毛竹叶片下表皮乳突和表皮毛数量逐渐变多,同一处理下的第1片叶到第5片叶,下表皮的乳突和表皮毛数量也逐渐变多;从T1—T8,毛竹幼苗叶下表皮气孔呈列排布,气孔表观形态虽无显著性差异,但气孔长度和气孔密度总体呈先上升后下降的趋势,气孔密度最高值主要集中在T5。【结论】26 ℃/18 ℃(T4),25 ℃/19 ℃(T5),24 ℃/20 ℃(T6)变温处理更利于促进毛竹种子发芽率和发芽势提高,综合幼苗的叶下高、叶片面积、发育速率、生物量、根系和气孔密度等各项指标,这3个组合变温处理更适宜幼苗总体生长发育。

Effects of variable temperatures on seed germination and seedling growth of Phyllostachys edulis

【Objective】The germination characteristics of moso bamboo seeds and the development law of seedlings with the 1-5 leaves were comprehensively studied after being cultivated in varying temperatures. This provided a theoretical and practical basis for the study of bamboo seedlings.【Method】The seeds were collected from Dajing Town, Lingchuan County, Guilin City in Guangxi Province. The seedlings were cultured in a laboratory incubator and seven different temperature treatments (two different temperature combinations within 24 hours) were set: 29 ℃/15 ℃ (T1), 28 ℃/16 ℃ (T2), 27 ℃/17 ℃ (T3), 26 ℃/18 ℃ (T4), 25 ℃/19 ℃ (T5), 24 ℃/20 ℃ (T6), 23 ℃/21 ℃ (T7), and one constant temperature environment 22 ℃/22 ℃ (T8). The temperature change period was 12 / 12 h. Every 12 hours, the germination time of each seed, the leaf development time of 1-5 leaves, and the leaf height under each environment of a different temperature were observed and recorded in detail. The leaf area, fresh and dry weights of the aboveground and underground parts, root morphology, leaf surface micromorphology, stomatal length and stomatal density were also measured.【Result】 ① The germination rate of P. edulis seeds was more than 50% under different temperature conditions. Combined with the germination potential of seeds, it was found that the germination potential of T4-T7 treatments was higher than 30%. In T1-T8 treatments, the mean germination time of the seeds was gradually shor-tened. ② Under different temperature conditions, the leaf development time of seedlings gradually extended from the first leaf to the fifth leaf. The time and quantity of leaf development were relatively concentrated in the T6-T8 treatments; meanwhile, leaf height and area of seedlings in the same culture environment gradually increased from the first leaf to the fifth leaf. Notably, the higher the temperature difference was, so did the leaf height increase. The development rate of leaves after the third leaf tended to be stable and it was observed that the larger the temperature difference, the larger the biomass of seedlings. In general, the root system developed better in T3-T6 treatments. ③ With the decrease in tempe-rature differences, the number of mastoid and epidermal hairs on the abaxial epidermis of P. edulis leaves gradually increased. From the first to the fifth leaf in the same treatments, the number of mastoid and epidermal hairs on the abaxial epidermis also gradually increased. In T1-T8 treatments, the stomata on the abaxial epidermis were arranged in rows. Although there was no significant difference in the appearance of the stomata, the length and density of the stomata ge-nerally increased first and then decreased, and the highest stomatal density was mainly concentrated in T5. 【Conclusion】The variable temperature treatments at 26 ℃/18 ℃ (T4), 25 ℃/19 ℃ (T5), and 24 ℃/20 ℃ (T6) were more conducive to improving the germination rate and germination potential of P. edulis seeds. Furthermore, the overall growth and development of the seedlings, including leaf height, leaf area, growth rate, biomass, root system and stomatal densities, were more suitable under these three different temperatures.