沙芥和斧形沙芥种子萌发对土壤含水量的适应性

以中国特有种沙芥[Pugionium cornutum(L.)Gaertn.]和濒危种斧形沙芥(Pugionium dolabratum Max-im.)的种子为研究材料,利用自然生境的沙土在室内进行种子萌发人工模拟试验,研究沙芥和斧形沙芥种子萌发、幼苗出土和幼苗生长对土壤含水量的适应性。结果表明:沙芥和斧形沙芥果实适宜萌发的土壤含水量范围均为6%～12%,适宜出苗的土壤含水量范围均为6%～16%。当土壤含水量低于2%时,果实不能萌发;当土壤含水量低于3%时,幼苗不能出土定居;当土壤含水量为6%～12%时,最有利于幼苗的生长。当土壤含水量分别为3%～8%和4%～8%时,沙芥和斧形沙芥植株根冠比最大。因此,沙芥和斧形沙芥种子萌发机制对沙生环境有着极强的适应性;植株将更多的同化物用于根系生长,以吸收更深层次的水分,从而适应含水量低的土壤。     

环境因子对奇异虉草和小子虉草种子萌发的影响

在室内条件下考察了环境因子温度、pH、盐分、土壤含水量以及种子埋深对外来入侵植物奇异虉草和小子虉草种子萌发和幼苗生长的影响,并与小麦进行对比研究.结果显示;(1)当温度为5℃、NaCl浓度为0.25 mol/L以及种子埋藏深度达到30 mm时,奇异虉草和小子虉草的种子完全不能萌发,而同等条件下小麦种子的发芽率分别依次为89.33%、53.33%和95.00%.(2)在pH 4.0～10.0和土壤含水量10.0%～25.0%条件下,奇异虉草和小子虉草的种子均能萌发;但pH在4.0和10.0以及土壤含水量低于15%时,其发芽率受到显著抑制;当土壤含水量为10%时奇异虉草和小子虉草的种子发芽率分别为19.33%和16.67%,而小麦种子的萌发完全受到抑制.(3)奇异虉草和小子虉草的幼苗最适生长环境为,温度25℃～30℃、pH为6.0～9.0、NaCl浓度0～0.05 mol/L以及种子埋藏深度为0～5 mm.研究表明温度、盐分和种子埋藏深度是影响奇异虉草和小子虉草种子萌发的关键因素,而偏碱性环境更有利于其种子萌发,其种子萌发对干旱胁迫的耐受性强于小麦.     

长芒草(Stipa bungeana)种子萌发与出苗对关键环境因子的响应

种子萌发为植物生活史的关键阶段,对植物的定居、群落演替与动态起着决定作用。通过室内控制实验的方法,研究长芒草(Stipa bungeana)种子萌发对光照和温度,水势和温度,以及幼苗出土对沙埋深度和供水的响应。使用光照、温度和湿度自动控制的生长箱,设置光照、黑暗和持续黑暗3个光处理和5个变温处理(5℃:15℃、10℃:20℃、15℃:25℃、20℃:30℃和25℃:35℃)(夜:昼);设置11个水势处理(0、-0.2、-0.4、-0.6、-0.8、-1、-1.2、-1.4、-1.6、-1.8 MPa和-2 MPa)和5个恒温处理(10、15、20、25℃和30℃),研究长芒草种子萌发对光照和温度、水势和温度的响应。设置6个沙埋深度(0.5、1、1.5、2、3、5 cm)和10个供水处理(2.5、5、7.5、10、15、20 mm和30 mm 7个单次供水处理,2.5、5、7.5 mm/3d 3个多次供水处理),研究长芒草幼苗出土对沙埋和供水的响应。结果表明:光照对长芒草种子萌发具有促进作用,黑暗与持续黑暗条件下的最终萌发百分率无显著差异。在10:20℃—15:25℃温度范围内,长芒草种子萌发快速且集中,15:25℃为种子萌发最适温度,超过最适温度时,最终萌发百分率随温度升高而下降。水势低于-1 MPa时长芒草种子不能萌发,最终萌发百分率和萌发速率均随水势的降低而降低。当温度达到30℃时,种子基本不能萌发。单次供水条件下,长芒草的最终出苗百分率和出苗速率接近为零;5 mm/3d及7.5 mm/3d供水条件下,最终出苗百分率可达到50%。5 mm/3d及7.5 mm/3d的多次供水与单次供水及2.5 mm/3d的多次供水相比更有利于长芒草出苗。适宜出苗的沙埋深度为0.5—2 cm,沙埋深度超过3 cm时最终出苗百分率和出苗速率均率接近于零。长芒草种子出苗情况随沙埋深度增加而降低,在供水量为7.5 mm/3d,沙埋深度为0.5—2 cm时,出苗最好。降低人为干扰对表层土壤的破坏,提高表层土壤含水量,是促进长芒草种子萌发和幼苗出土的有效措施。     

水分对胡杨幼苗光合及生长特性的影响

采用盆栽控制实验方法对不同水分条件下胡杨幼苗的光合日变化以及生长特性进行分析研究.结果显示:(1)不同水分条件下胡杨幼苗的净光合速率(Pn)、气孔导度(Gs)、胞间CO2浓度(Ci)和蒸腾速率(Tr)日变化曲线均呈单峰型,峰值时间均在12:00;当土壤含水量为21.6%～24.0%时,幼苗的水分利用效率(WUE)日变化曲线呈不明显的双峰型,峰值时间分别在8:00和18:00,其他处理均为单峰型,但峰值时段有差异;随着土壤含水量的减小,胡杨幼苗的Pn、Gs、Ci和Tr日均值逐渐降低,当土壤含水量为12.0%～19.2%时,幼苗的WUE日均值显著高于其他处理.(2)幼苗的株高、基径、各器官的生物量及总生物量均随土壤含水量的减小而降低,当土壤含水量为12.0%～19.2%时,幼苗地下生物量的降低程度大于地上生物量,且幼苗的根冠比也增大.研究表明,土壤含水量对胡杨幼苗的光合特性及其生长具有显著影响,当土壤含水量大于12.0%时,幼苗能够通过增大水分利用效率,改变根冠比提高抗旱性;当土壤含水量小于9.6%时,幼苗自我调节能力减弱,生长受到抑制.     

紫花苜蓿和羊草种子出苗和幼苗生长对土壤含水量的响应

土壤含水量是种子萌发和幼苗生长阶段的关键环境因子。采用室内模拟方法,研究了不同土壤含水量(2.5%、5%、7.5%、10%、20%和30%)对紫花苜蓿和羊草种子出苗和幼苗生长的影响。结果表明:苜蓿和羊草种子的出苗率和幼苗的生长均显著受土壤含水量的影响;随着土壤含水量的增加,苜蓿和羊草的出苗率均呈先上升后下降的趋势;其中,苜蓿种子在土壤含水量为10%~20%时出苗率最高(93%),土壤含水量为30%时最低(2%);在5%土壤含水量时羊草出苗率最大(76%),在30%含水量时最低(9%);随着含水量增加,紫花苜蓿和羊草幼苗根苗长均表现为先上升后下降的趋势,土壤含水量7.5%~10%更适宜于紫花苜蓿种子出苗及幼苗生长,羊草种子的最适土壤含水量为5%~7.5%;综合出苗率和幼苗的生长情况,适宜苜蓿和羊草播种和幼苗生长的土壤水分含量分别为7.5%~10%和5%~7.5%。     

浑善达克沙地黄柳种子发芽和幼苗生长特性的研究

在实验室通过模拟野外自然条件,研究了土壤水分、沙埋厚度和温度对黄柳种子发芽与幼苗生长的影响。结果表明:(1)黄柳种子对水分条件很敏感,发芽的适宜土壤含水量为3%~20%,低于3%或高于20%发芽都会受到抑制;(2)种子萌发需要沙土覆盖,适宜覆沙厚度为0.1~0.4 cm,此条件下第5天种子发芽率达80%以上;但当沙埋厚度超过0.6 cm时,种子出苗就会受到抑制;当沙埋厚度超过1.2 cm时,将不能出苗;(3)种子发芽的适宜温度为15~35℃,当温度高于45℃时种子将不能萌发并最终死亡;(4)幼苗的耐热性较强,40℃处理下幼苗出现热害症状,并且热害症状发展缓慢,60℃处理下90 min后幼苗干枯死亡;(5)种子的寿命为120 d左右。     

温度和土壤含水量对青冈栎种子萌发的影响

运用直播法,研究应用人工气候箱控制温度和土壤含水量对野生青冈栎种子萌发和幼苗生长的影响。结果表明:在12h光照条件下,青冈栎种子在变温为10℃/15℃时,萌发率很低,仅为(12±12.29)%;变温为30℃/35℃时,萌发率达最大,为(81±13.7)%。土壤含水量为30%～40%时,萌发率为(79±15.9)%;土壤含水量为90%～100%时,萌发率为(56.67±19.36)%。青冈栎种子萌发呈现出迅速萌发和推迟萌发的特点;温度对青冈栎幼苗的苗高、叶长和叶宽影响显著,对幼苗的地径、叶片数量影响不显著。恒温下,不同梯度土壤含水量处理对幼苗的苗高、地径、叶长、宽影响不显著。     

沙埋对无芒雀麦种子萌发和幼苗生长的影响

研究了沙埋对浑善达克沙地植物群落中多年生禾草无芒雀麦种子萌发、出苗和幼苗生长的影响.结果表明:无芒雀麦种子能在深度≤12cm的沙埋中萌发,≤8cm的沙埋中出苗.在此范围内,随着沙埋深度的增加,无芒雀麦种子的萌发率和出苗率逐渐降低.沙埋深度在植株高度的33%时,无芒雀麦1周龄和2周龄幼苗均全部存活,且总生物量≥对照(未沙埋幼苗);当沙埋深度增至植株高度的66%时,1周龄和2周龄幼苗的存活率分别降至70%和25%,生长也受到抑制;而遭受全部沙埋时,1周龄和2周龄幼苗均不能存活.遭受沙埋后,无芒雀麦幼苗分配较多的生物量用于地上部分的生长,其生物量分配模式改变可能是无芒雀麦幼苗对沙埋环境的重要适应对策.     

西鄂尔多斯珍稀濒危植物长叶红砂种子萌发特征

珍稀濒危灌木长叶红砂是我国西北干旱地区荒漠植被中的古老残遗物种,对维持荒漠植被稳定具有重要作用.本文研究了长叶红砂种子特性,及其在不同光照、温度、土壤水分和沙埋等环境因子中的萌发策略.结果表明:长叶红砂种子具有高活力、高萌发率、耐贮存的特点,在光照和黑暗条件下均能很好地萌发.种子萌发的适宜温度为恒温20 ℃～25 ℃或变温15 ℃/25 ℃,萌发率高达93%.土壤含水量为2%时,种子开始萌发;土壤含水量为12%时,其萌发率最高,达89%.长叶红砂种子适宜的沙埋深度为1 cm,＞5 cm沙埋不出苗.沙埋深度对出苗率和幼苗生长高度的影响显著,而对幼苗质量的影响不显著.水分条件和沙埋深度是制约长叶红砂种子萌发和出苗的主要因素,而种子的高萌发率增加了幼苗生存的风险,不利于其应对荒漠极端环境变化.这种特性是长叶红砂濒危的重要原因之一.     

土壤水肥因子对胡杨幼苗生长权衡和木质化的影响

以当年生胡杨幼苗为材料,通过不同水平的水分和养分单因素控制盆栽试验,探讨土壤水肥因子对当年生胡杨幼苗生长权衡和木质化的影响,以明确胡杨生长过程中以及种子更新困难的原因和机理。结果表明:(1)当年生胡杨幼苗生长权衡主要体现在生物量的分配策略上,而主根长/高度没有显著差异。(2)在连续给水处理下,干旱胁迫使幼苗根冠比显著增加,土壤含水量15%处理的根冠比较含水量20%和30%处理分别显著增加了75%和93%;但干旱胁迫抑制了生物量的积累,含水量10%处理下生物量比15%、20%和30%处理分别显著减小53.4%、89.2%、78.6%;在断续给水处理下,随着干旱程度的增加幼苗根冠比显著增加,土壤含水量15%处理的根冠比较含水量20%和30%处理分别显著增加34%和38%;连续给水和断续给水两类干旱胁迫均能明显增加幼苗根系木质化程度。(3)土壤施加氮磷均显著增加幼苗根冠比和木质化,但过量的氮肥抑制根系生物量的积累。可见,胡杨幼苗对于水肥条件胁迫敏感性与生长权衡能力是胡杨林种子更新与种群维持的关键环节,调整立地土壤水肥环境对当年生胡杨幼苗的生长定居有重要的作用。     

Responses of Caryopsis Germination, Seedling Emergence, and Development to Sand Water Content of Agropyron cristatum （L.） Gaertn. and Bromus inermis Leyss.

Responses of caryopsis germination, seedling emergence, and development of Agropyron cristatum （L.） Gaertn. （Gramineae） and Bromus inermis Leyss. （Gramineae）, two dominant perennial grasses in the Otindag Sandland of China, to different sand water content （SWC; 1%, 2%, 3%, 4%, 6%, 8%, 12%, 16%, and 20%） were studied comparatively. The results showed that the germination responses of the two grasses to SWC were similar （i.e. caryopses could not germinate when the SWC was below 3%; at SWC ranging from 3% to 12%, the higher the SWC, the higher the germination percentage; and at a SWC of 12%-20%, germination reached similarly high percentages）. At a sand burial depth of 0.5 cm, the threshold of SWC for seedling emergence was 6% forA. cristatum and 8% forB. inermis; at 12%-20% SWC, the seedling emergence of both species reached similarly high percentages. The seedling growth responses of these two species to SWC gradients were different. For A. cristatum, the biomass of seedlings increased with SWC from 6% to 12%, and decreased with SWC from 12% to 20%. For B. inermis, the biomass of seedlings always increased with SWC from 8% to 20%. The results also showed that the seedlings of both species allocated more biomass to the roots with decreases in SWC. The SWC changes from April to October in natural microhabitats of both species suggested that the SWC may play an important role in caryopsis germination, seedling emergence, and the growth characteristics of the two grasses. The responses of caryopsis germination, seedling emergence, and the growth characteristics of these two species to SWC may determine their distribution pattems in the Otindag Sandland.     

Responses of Caryopsis Germination, Seedling Emergence, and Development to Sand Water Content of Agropyron cristatum (L.) Gaertn. and Bromus inermis Leyss.

Responses of caryopsis germination, seedling emergence, and development of Agropyron cristatum (L.) Gaertn. (Gramineae) and Bromus inermis Leyss. (Gramineae), two dominant perennial grasses in the Otindag Sandland of China, to different sand water content (SWC; 1%, 2%, 3%, 4%, 6%, 8%, 12%,16%, and 20%) were studied comparatively. The results showed that the germination responses of the two grasses to SWC were similar (i.e. caryopses could not germinate when the SWC was below 3%; at SWC ranging from 3% to 12%, the higher the SWC, the higher the germination percentage; and at a SWC of 12 %, germination reached similarly high percentages). At a sand burial depth of 0.5 cm, the threshold of SWC for seedling emergence was 6% forA. cristatum and 8% forB. inermis; at 12%-20% SWC, the seedling emergence of both species reached similarly high percentages. The seedling growth responses of these two species to SWC gradients were different. For A. cristatum, the biomass of seedlings increased with SWC from 6% to 12%, and decreased with SWC from 12% to 20%. For B. inermis, the biomass of seedlings always increased with SWC from 8% to 20%. The results also showed that the seedlings of both species allocated more biomass to the roots with decreases in SWC. The SWC changes from April to October in natural microhabitats of both species suggested that the SWC may play an important role in caryopsis germination,seedling emergence, and the growth characteristics of the two grasses. The responses of caryopsis germination, seedling emergence, and the growth characteristics of these two species to SWC may determine their distribution patterns in the Otindag Sandland.     

沙埋对醉马草种子萌发和幼苗生长的影响

为探讨醉马草(Achnatherum inebrians)种群繁殖和扩散机理,并为其防控和开发利用提供理论基础,研究了不同沙埋深度(0、1、2、3、4和5cm)对醉马草种子萌发和幼苗生长的影响。结果表明:埋深对醉马草幼苗出土率、首次出苗时间、幼苗生长高度以及生物量的分配均有极显著影响(P<0.001);种子萌发和幼苗出土率在2cm沙埋下达到最高(92%),在5cm沙埋下最低(58.7%);幼苗最大高度(10.8cm)出现在3cm的沙埋,最小高度(6.3和7.1cm)出现在0和5cm的埋深;埋深为2cm时,地上和地下生物量最大,埋深5cm时地上和地下生物量均最小;最大根长(约5cm)和最小根长(1cm)分别出现在2～3cm和5cm的埋深。2～3cm的埋深是醉马草种子萌发和幼苗生长的最佳深度。     

Caryopsis germination and seedling emergence in an inland dune dominant grass Leymus secalinus

Leymus secalinus (Georg.) Tzvel. (Poaceae) is a dominant sand dune grass inhabiting the Mu-Us Sandland, semiarid China. Freshly harvested caryopses (seeds) are in non-deep physiological dormancy (non-deep PD) because of low percentage and slow rate of germination. Experiments were conducted to examine the effects of temperature, cold stratification, caryopsis coat scarification or partial removal of endosperm and sand burial on caryopsis dormancy, germination and seedling emergence. Caryopsis germination was significantly influenced by duration of cold stratification, temperature and their interactions. After 8 weeks of cold stratification, caryopsis germination percentage at 30 °C reached to 90%, equally in light or darkness. Rate and percentages of germination were also hastened and increased by scarifying the caryopsis coat or by artificial removal of different proportions of the endosperm. However, seedling developmental characteristics were significantly influenced by the proportion of the endosperm that remained in the caryopses. Seedling emergence, caryopsis germination and enforced dormancy in sand were significantly affected by sand burial depth. As sand burial depth increased, caryopsis germination and seedling emergence decreased whereas caryopsis enforced dormancy increased. 1–2 cm was the optimal depths for caryopses germination and seedling emergence. Although there were still 30% caryopses germinated at 8 cm, the maximal burial depth for seedling emergence was only 4 cm. The partial germination strategy regulated by non-deep PD, temperature and sand burial ensures that only a few caryopses germinated each time and may reduce risks for seedling survival.     

Seed germination and seedling emergence of three annuals growing on desert sand dunes in China

BACKGROUND AND AIMS: Information on the initial growth characteristics of annuals found in Chinese deserts is very limited. The aim of this study was to investigate seed germination and interactive effects of irrigation and seed burial depth in sand on seedling emergence and seedling survival in three annuals (Agriophyllum squarrosum, Bassia dasyphylla and Aristida adscensionis) commonly growing on sand dunes in these regions. METHODS: Effects of temperature, light and polyethylene glycol-6000 on seed germination were examined by irrigating seeds sown on filter paper in Petri dishes. Seedling emergence was examined for seeds sown on the surface of, or at different depths (5, 10, 20, 30, 40 and 50 mm) in, sand-filled pots, which were irrigated under different regimes. For seeds buried at a depth of 50 mm, seed viability was examined after irrigation of the pots. KEY RESULTS: Seeds of three species germinated at most temperatures recorded between spring and autumn in their native habitats. No seed dormancy was found in any species. For all three species, seedling emergence was most favoured when seeds were buried at a depth of 10 mm. When seeds sown on the sand surface were irrigated, seed germination was considerably suppressed due to water deficiency, but many seeds remained viable. For A. squarrosum and B. dasyphylla, many seeds that were deeply buried and irrigated remained ungerminated but viable, while for A. adscensionis deeply buried seeds germinated, but the seedlings did not emerge due to unfavourable seedling growth in deep sand. CONCLUSIONS: Precipitation is the most crucial factor in determining the seasonal emergence of seedlings of the three tested species in the field. The vertical distribution of seeds in sand determines the proportion of seeds that germinate after precipitation and acts to maintain seed banks over multiple years.     

Effects of sand burial depth on seed germination and seedling emergence of Cirsium pitcheri

A greenhouse study was conducted to determine the effects of sand burial on seed germination and seedling emergence of Cirsium pitcheri, a threatened species along Lake Huron sand dunes. In October 1996, seeds of C. pitcheri were sorted into three groups (small, medium and large) and artificially buried at 2, 4, 6, 8, 10 and 12 cm depths in plastic pots filled with unsterilized sand from Lake Huron sand dunes. These pots were placed outside in sand boxes for natural stratification. In early February, the pots were brought into the greenhouse for germination of seeds. Data showed that percent seed germination and emergence of seedlings were not related to seed size. However, both variables were negatively correlated with depth. Seedling emergence occurred from a maximum depth of 6 cm with most seedlings emerging from 2 cm depth. Only one seedling emerged from 8 cm depth. Seedlings from large seeds produced longer roots than those of small seeds. Larger root system would probably enhance seedling establishment.     

沙埋对花棒种子萌发和幼苗生长的影响

为探讨花棒(Hedysarum scopariium)种子萌发和幼苗生长对沙埋的响应,并为固沙造林、水土保持提供理论基础,研究了6种沙埋深度(0、1、2、3、4和5cm)对花棒种子萌发和幼苗生长的影响.结果表明,埋深对花棒幼苗出土率、首次出苗时间、单株叶片数、幼苗生长高度以及生物量的分配均有极显著影响(P<0.001).种子出苗率在2 cm沙埋下达到最高(95.6%),在5cm沙埋下最低(43.4%);幼苗最大高度(11.6cm)、绝对株高(13.9cm)和最大地上生物量(26.7mg)均出现在2cm的埋深,幼苗最小高度(3.3cm)、最小根长(4.3cm)和最小地上生物量(5.3mg)出现在5cm的埋深;生物量分配随沙埋深度增大而更多地分配给地下部分.2cm的沙埋是花棒种子萌发和幼苗生长的最佳深度.