朱唇种子吸水特性及其在干旱胁迫下萌发特性

Water absorption properties of Salvia coccinea seed and its germination characteristics under drought stress

关键词:  朱唇, 种子, 粘液, 萌发

Key words:   Salvia coccinea, seed, mucilage, germination

摘要:

种子粘液质是植物在长期适应环境过程中形成的,该物质对于种子的扩散、定居、生存力的改善、萌发、幼苗生存乃至抵御有毒化学物质毒害等都具有重要的生态学意义。朱唇为唇形科鼠尾草属多年生草本植物,原产美洲热带地区,现已广泛栽植于世界各地。为了理解朱唇种子表面的粘液物质吸水特性和种子在干旱胁迫下的萌发特性,该研究以朱唇种子为材料,运用光学显微镜和扫描电子显微镜观察以及种子萌发试验的方法,对种子和粘液层的形态结构、粘液质对种子萌发的影响进行了研究。结果表明:朱唇种子为卵形,表面为负网状结构,千粒重为(1.611±0.0084)g,无粘液种子吸水倍数为3,粘液种子吸水倍数为25,粘液层吸水倍数为122。粘液和无粘液种子及粘液层的重量都随吸水时间的延长而增长,但脱水过程要远长于吸水过程。朱唇种子吸水2 h达到饱和,经过36 h可干燥失水恢复原重。不同浓度PEG对朱唇种子的萌发均有影响,发芽势随PEG浓度升高而显著降低。朱唇种子在5%PEG胁迫下发芽率最高达(90.00±8.66)%,20%PEG胁迫下发芽率最低为(76.67±10.41)%,低浓度PEG对朱唇种子萌发有一定促进作用。这说明朱唇种子为速萌型种子,其粘液质在种子吸水过程中起到举足轻重的作用,能保证短时间内有充足的水分供其萌发。

Abstract:

Producing mucilage is a survival strategy of plants that formed in the long-term process of their environment adaptation, and the seeds producing mucilage are called mucilaginous seeds or mucus propagule. Studies show that mucilage has important ecological significance for the dispersal, settlement, viability improvement, germination, survival of seedlings and even the resistance toward the poisoning of toxic chemicals of seeds. Salvia coccinea is a perennial herb(Lamiaceae: Salvia)originating in the tropical regions of the American continent. Due to its high medicinal and ornamental value, S. coccinea is widely cultivated throughout the world. In order to understand the water absorption properties of mucilage on the seeds of S. coccinea and germination characteristics of S. coccinea seed under drought stress. In the present study, seeds of S. coccinea were studied on the morphology and water absorption of seed coat mucilage and seed germination under the drought stress which was created with different concentrations of PEG. The study methods were light micro-scope, scanning electron microscopy observation and seed germination test. The results showed that seeds of S. coccinea were spherical; 1 000-grains weight of the seeds was(1.611±0.0084)g; seeds without mucilage were able to absorb an amount of water of 3 times of their own dry weights; seeds were 25 times of their own dry weights; mucilage was 122 times of its own dry weight. The results indicated that the weights of mucilaginous seeds, non-mucilaginous seeds and mucilage layer increased with the extension of time, but the process of dehydration was much longer than that of absorption. Water absorption of the seeds reached saturation 2 h after watering, and the water saturated seeds were dehydrated to their original dry weights in 36 h after being exposed to air at room temperature. PEG of different concentrations had various impacts on the seed germination of S. coccinea, and the germination potential decreased significantly with the increase of PEG concentration. Seed germination rate was as high as(90.00±8.66)% under 5% PEG and as low as(76.67±10.41)% under 20% PEG. In conclusion, S. coccinea seeds are characterized by fast germination. Mucilage plays a decisive role in the water absorption process of seeds and ensures sufficient moisture supply for seed germination in a short time.