作 者 ：丁琼, 王华, 贾桂霞, 郝玉光
期 刊 ：植物生态学报 2006年 30卷 4期 页码：633-639
Keywords:Ammopiptanthus mongolicus, Soaking, Temperature, Germination percentage, See d size, Seedling emergence,
摘 要 ：沙冬青（Ammopiptanthus mongolicus）是亚洲中部荒漠特有种，由于其分布的环境条件特殊，现存植被天然更新困难，人工育苗、造林存在一定问题。为改善种皮透水性，获得整齐一致的发芽，分别用21.5 (室温)、40、60、80和90 ℃的温水浸种5 min。结果表明：60 ℃温水浸种效果最好，与对照相比，显著地提高了种子发芽势，并有效地降低硬实率。对比分析了15、20、25、30、35和40 ℃环境温度下种子萌发的特性，种子发芽最适温度是30 ℃，而胚根及下胚轴伸长最快的温度为25～30 ℃ 。较低温度下种子发芽延续时间较长，并且种子萌发后下胚轴和胚根伸长缓慢，易形成畸形（胚根严重扭曲、缢裂）幼苗。15 ℃时畸形幼苗占发芽种子数的28.1％，而30～40 ℃时 仅占5.2%～8.6%。温度过高不利于种子萌发及幼苗生长，40 ℃时，吸胀种子绝大部分丧失活力，发芽种子在35 ℃以上温度下生长2～3 d，胚根胚轴组织呈水渍状坏死。另外，催芽后的种子播种在河沙中子叶出土最快，出土率可达63%，显著高于在粘质壤土中出土率（11%）。不同粒径的种子播种后幼苗生长特性表现出一定的差异，粒径5 mm以下小粒种子播种后幼苗长 势弱，苗期成活率低，生长70 d后幼苗成活率仅为35.4%，而粒径5 mm以上种子同期幼苗成活率达 56.2%。据上述试验结果，结合自然分布区内环境条件的资料，分析了沙冬青濒危原因，并为植被恢复育苗措施提出建议。
Abstract:Background and Aims Ammopiptanthus monglicus, endemic to the semi_arid desert region of
central Asia, is an endangered evergreen leguminous shrub. Having difficulties to recruit
into its original habitat, A. mongolicus population is experiencing difficulties in
regeneration, and the area it ever possessed is shrinking. It is included in the China Red
Data Book of Endange red Plant as the third_class protected plant. Despite the importance
of seed germination characteristics in developing an adequate understanding of both primary
and secondary colonization processes, there still not a few previous studies on the
germination of A. mongolicus. To get a comprehensive understanding about the germination
characteristics and seedling performance ofA. mongolicus, experiments were, therefore,
conducted to define the optimum environmental condition for germination. Further, the seed
size effects on the seedling performance is also investigated here.
Methods In order to find out optimal temperature for soaking, Seeds were soaked in water of
21.5 (room temperature), 40, 60, 80, 90 ℃ for 5 minutes respectively . Treated seeds were
placed on moistened filter papers in 11cm diameter Petridishes, then, transferred into a
laboratory incubator at 28 ℃. To test the germination response of the seed to the
environmental temperature, seeds presoaked in 60 ℃ hot water were put into incubator under
15, 20, 25, 30, 35, 40 ℃ for germination, respectively. In the case of container seedling
culture, presoaked seed were sowed with different cultural media, sandy soil, clay loam,
mixed soil (sand soil mixed with clay loam at the ratio of 1∶1). Attempt to answer the
question that whether the seeds with different size will differ in seedling performance,
seeds were categorized into three groups according to the their diameter, those less than 5
mm, those between 5 and 6 mm, and those that of more than 6 mm. Pretreated seeds of its
respective size were sowed into the raised seedbed separately. Observations on the
seedlings survival rate, leaf width, leaf number, and plant height were recorded almost
twice a month.
Key Results Seeds presoaked in water at 60 ℃, gave the highest germination vigor that
56.4% seeds were germinated within one day’s incubation at 28 ℃. The optimal temperature
for hypocotyl and radicle elongation of seedling is 25 ℃ to 30 ℃, lower than that for
seed germination initiation (30 ℃). Temperature above 40 ℃ would likely have a
detrimental effect on seedling growth in the germination test, it cause the hypocotyl and
radical tissue damage and eventually decay of the seedlings. Interestingly, the percentage
of abnormal seedlings with tightly twisted radicle and split tip, which are less likely to
survive in the seedbed, were just 5.2%-8.6% under the temperature of 30 ℃ to 40 ℃,
greatly less than that of 28 .1% under the temperature of 15 ℃. In the case of container
seedling culture, sixty three percent seedlings emerged out of the sand soil within 7 days,
while in clay loam only 11%. Compared with seedlings emerged from the smaller one,
seedlings emerged from seeds with size more than 5 mm tend to be stronger and growing more
vigorous than the smaller one during the early stages of growth. This trend is further
evidenced by the weak and high susceptibilities to pathogen and continuous death of
seedlings from the smaller seeds within the 70 days growth. Seedlings from larger seeds
took only about 57 days to attain a constant survival rate of more than 56.3%, while
seedlings from the smaller ones took more than 70 d ays to attain 35.4% and still on a
decreasing trend.
Conclusions Extremely high or low temperature have a detrimental effect on germination and
seedlings performance of A. mongolicus shortly after the germination initiation, despite
the fact that their adult counterpart have a extremely high tolerance to the hardness of
its environment. This is accordance with our filed observation that very few seedlings or
saplings were seen in the natural habitat . Soaking in hot water between 40 ℃ to 60 ℃ did
promote the germination rate o fA. mongolicus, and decrease the percentage of remaining
hard_coated seeds. Seeds less than 5 mm in diameter showed reductions in seedling quality
and seedling performance suggests that seeds with different size may have significant
impacts on future community composition in the prospect habitat and should be treated disc
riminatingly in nursery and re_introduction activity.