不同温度条件下PEG模拟干旱胁迫对水杉种子萌发的影响

Influences of PEG simulating drought stress on seed germination of Metasequoia glyptostroboides under different temperatures

关键词:  水杉, 原生地春季低温, 发芽率, 发芽势, 发芽指数

Key words:  Metasequoia glyptostroboides, spring low temperature in original habitat, germination rate, germination energy, germination index

摘要:

水杉原生种群天然更新极差,林下鲜见幼苗和幼树,种子萌发率低是造成天然更新困难的重要因素。为探究其种子萌发率低是否与水杉母树原生地春季低温有关,该文利用恒温培养箱设置3种恒温处理(15、20、25 ℃)和1种变温处理(12 ℃/12 h和24 ℃/12 h,每24 h交替),并设置5种不同浓度的聚乙二醇(PEG-6000,0、0.05、0.10、0.15、0.20 g·mL^-1)模拟干旱胁迫,来研究干旱胁迫对水杉种子萌发的影响。结果表明:(1)实验所设置的温度对水杉种子萌发无显著影响(P>0.05),变温条件下的水杉种子平均发芽率和发芽势均为最高,分别为46.75%和21.25%;(2)不同浓度的PEG-6000溶液对其种子萌发产生显著影响(P<0.05),水杉在15 ℃或25 ℃下,低浓度的PEG-6000溶液(0～0.10 g·mL^-1)对水杉种子的发芽势和发芽指数有促进作用,高浓度(>0.10 g·mL^-1)的PEG-6000溶液对水杉种子的萌发有抑制作用,且随着浓度的增大抑制作用也随之增强,直到浓度增大为0.20 g·mL^-1 时,水杉种子不再萌发。原生地春季低温并不是造成水杉原生种群天然更新困难的因素,适当的干旱胁迫有利于增强水杉种子发芽势和发芽指数,促使出苗整齐。

Abstract:

Regeneration of original species of Metasequoia glyptostroboides is very difficult in nature, and seedlings and saplings are rarely seen under the forest. Low spring temperature in original habitat of M. glyptostroboides is an important factor causing the difficulty of natural regeneration. To explore whether the reason for the low seed germination rate is related to the spring low temperature of the original species of M. glyptostroboides. We used constant temperature incubator to set three kinds of constant temperature treatment(15, 20, 25 ℃)and one kind of temperature change treatment(12 ℃/12 h and 24 ℃/12 h, alternating every 24 h); set five different concentrations of polyethylene alcohol(PEG-6000, 0, 0.05, 0.10, 0.15, 0.20 g·mL^-1)mimics drought stress. The results were as follows:(1)The temperature set by the experiment had no significant effect on the germination of M. glyptostroboides seed(P>0.05). The average germination rate and germination potential of M. glyptostroboides seeds under variable temperature conditions were the highest, which were 46.75% and 21.25%, respectively;(2)Different concentrations of PEG-6000 solution had significant effects on seed germination(P< 0.05), at the temperatures of 15 ℃ or 25 ℃, low concentration of PEG-6000 solution(0-0.10 g·mL^-1)promoted the germination potential and germination index of M. glyptostroboides seeds, high concentration(>0.10 g·mL^-1)PEG-6000 solution inhibited the germination of M. glyptostroboides seed, and the concentration increase inhibition also increased, and until the concentration increased to 0.20 g·mL^-1, the M. glyptostroboides seeds no longer germinated. The results indicate that the low temperature in the spring is not a factor that causes the natural regeneration of the original population of M. glyptostroboides, and appropriate drought stress is beneficial to enhance the germination potential and germination index of M. glyptostroboides seeds, and to promote the emergence of seedlings.