无瓣海桑幼苗对不同遮光度的生理生态响应

依据实地测定人工无瓣海桑红树林不同环境下的光照强度,研究了无瓣海桑幼苗在不同遮光度环境中的生理生态响应。结果表明,随着遮光度的增大,无瓣海桑的种子萌发、幼苗的生理生态指标水平均呈下降趋势。在80%和40%全光照下,幼苗的茎高、基径、节数和叶片数下降。当光强为全光照的20%即遮光过度时,幼苗就表现出生长严重受阻的响应。弱光环境下无瓣海桑种子的发芽率很低,无瓣海桑幼苗叶片的叶绿素含量、净光合速率、可溶性总糖含量和硝酸还原酶活性等生理参数均呈下降趋势,且各处理间差异显著。试验表明,弱光条件是造成无瓣海桑幼苗生理指标水平低下和死亡率较高的主要原因,并对无瓣海桑的天然更新与自然扩散和人工造林技术进行了讨论。     

盐度对无瓣海桑幼苗的生长和某些生理生态特性的影响

本文研究了盐度（０‰～５０‰）对无瓣海桑幼苗生长的影响。盐度对无瓣海桑幼苗长叶数、茎长、植株鲜重、主根长、根系鲜重等方面起抑制作用;随盐度的提高,无瓣海桑幼苗成活率下降;但盐度对无瓣海桑幼苗叶片面积存在一个低盐（０‰～１０‰）促进、高盐（１５‰～４０‰）抑制的过程;盐度对叶绿素含量的影响总趋势是随盐度提高,低盐时叶绿素含量下降,而当盐度超过１０‰时上升。因此认为：１）无瓣海桑幼苗在无盐存在下,也可     

盐度对无瓣海桑幼苗的生长和某些生理生态特性的影响

本文研究了盐度(0‰～50‰)对无瓣海桑幼苗生长的影响。盐度对无瓣海桑幼苗长叶数、茎长、植株鲜重、主根长、根系鲜重等方面起抑制作用;随盐度的提高,无瓣海桑幼苗成活率下降;但盐度对无瓣海桑幼苗叶片面积存在一个低盐(0‰～10‰)促进、高盐(15‰～40‰)抑制的过程;盐度对叶绿素含量的影响总趋势是随盐度提高,低盐时叶绿素含量下降,而当盐度超过10‰时上升。因此认为：1)无瓣海桑幼苗在无盐存在下,也可正常生长;2)无瓣海桑具有较高的耐盐能力,在盐度0‰～25‰内可正常生长,超过25‰,其生长受到抑制。     

2010年冬季寒冷天气对闽江口3种红树植物幼苗的影响

2010年10月8日-2011年2月26日,跟踪监测了闽江河口互花米草治理试验区人工种植的秋茄(Kandelia candel)、无瓣海桑(Sonneratia apetala)和拉关木(Leguncalaria racemosa)1年生幼苗叶片相溶性物质含量以及活性氧代谢等生理生化指标.结果表明:可溶性糖和脯氨酸含量均随气温的逐步降低而增加,秋茄可溶性糖含量最高,拉关木脯氨酸含量最高;整个监测期无瓣海桑和拉关木幼苗叶片超氧阴离子(O2)产生速率显著高于秋茄(P＜0.01),而超氧化物歧化酶(SOD)和过氧化物酶(POD)活性显著低于秋茄(P＜0.01);3种植物叶片丙二醛(MDA)含量及电解质渗透率均随着气温的降低而增加,其中无瓣海桑和拉关木MDA含量及电解质渗透率与日最低气温为显著和极显著的负相关关系.2010年冬季持续寒冷天气对闽江河口湿地1年生土著种秋茄幼苗无破坏,对引进种无瓣海桑和拉关木造成了严重的低温胁迫并使幼苗基本全部死亡.     

苗期无瓣海桑与互花米草的营养竞争关系研究

采用间植分隔法开展了无瓣海桑和互花米草营养竞争关系研究,结果表明竞争作用刺激了无瓣海桑高、径、冠幅、分枝及叶片数的增长,却抑制了叶面积的增加。地上竞争可增加无瓣海桑的地上生物量,但对根冠比影响不大。地下竞争增加了互花米草的地上生物量,降低了其根生物量,此时根冠比最小。地下竞争促进了无瓣海桑的主根生长,抑制了侧根生长,而地上竞争则正相反;随着竞争程度的加深,根活力逐渐降低。地下竞争时互花米草根活力显著下降。无瓣海桑和互花米草在有地上竞争时叶绿素a和b的含量均降低。各竞争处理未对P、K、Ca和Mg元素的含量产生显著影响,但地上竞争显著降低了N元素在无瓣海桑和互花米草根茎叶中的含量。互花米草的竞争强度略高于无瓣海桑,但是地上竞争强度无瓣海桑远远高于互花米草,而二者地下竞争强度相当。     

无瓣海桑与乡土红树植物混交对林地大型底栖动物的影响

选择广东省雷州市附城镇和珠海市淇澳岛沿海1年生无瓣海桑人工林,分别在林下混种乡土红树植物红海榄或木榄幼苗,对混交林和无瓣海桑纯林林地大型底栖动物群落进行比较,探讨无瓣海桑与乡土红树植物混交对林地大型底栖动物的影响。结果显示,混交林和无瓣海桑纯林之间大型底栖动物群落的优势种存在差异;相似性分析检验(One-Way ANOSIM)、等级聚类和非参数多变量标序结果均表明1年无瓣海桑+红海榄混交林、1年无瓣海桑+木榄混交林和1年无瓣海桑纯林之间大型底栖动物群落结构差异显著。研究还发现在无瓣海桑人工林林下混交红海榄或木榄这两种乡土红树植物,可提高林地底栖动物的生物量和物种多样性。BIOENV分析说明大型底栖动物分布与红海榄或木榄这两种混交的乡土树种的凋落物量密切相关,这进一步证实了混交乡土红树植物对林地底栖动物多样性和分布的影响。两个研究地实验结果均显示,在无瓣海桑林下种植木榄的效果要优于红海榄,表现在木榄的平均苗高、凋落物量、凋落物量占群落凋落物总量百分比和幼苗成活率均高于红海榄,其对提高林地大型底栖动物生物量和物种多样性的效果也明显优于红海榄。     

无瓣海桑和秋茄人工林的减风效应

以海南东寨港三江湾无瓣海桑和秋茄人工林为研究对象,观测红树林内距向海林缘50 m、地面以上2 m高处的风速、风向特征,研究红树林的减风效应.结果表明:无瓣海桑和秋茄人工林均对偏北方向由海向岸的风速有明显的减弱效应,林带内50 m处的平均风速减低85％以上,并且秋茄林的减风效应更显著.随着风速的增加,林分的减风效能呈先下降后平缓的趋势.当风速低于5m·s-1时,无瓣海桑人工林内50 m处的平均风速减低89.8％;当风速在lOm·s-1以上时,其风速减低率趋于稳定;当风速＞15 m·s-1时,平均风速减低58.9％ ～63.6％.与冷季相比,无瓣海桑人工林暖季的减风效应更显著.在台风等极端天气状况下,无瓣海桑人工林内50 m处的平均风速和极大风速分别减低59.4％和53.2％.     

深圳湾红树林引种海桑、无瓣海桑的生态评价

对深圳湾红树林引种的外来种海桑(Sonneratia caseolaris (L.) Engl.)和无瓣海桑(S. apetala B. Ham.)的生态适应性、扩散现状及生态入侵的可能性进行了研究.结果表明:海桑和无瓣海桑对深圳湾的气温、盐度、潮滩与土壤等基本适应,虽然极端低温是其生长定居的限制因子,但其子代的抗寒性逐渐增强,在局部区域有一定的繁殖力和扩散力,生态效益明显.从种群生物生态学特性、生态位理论、群落更新理论等方面分析认为,海桑和无瓣海桑在深圳湾造成生态入侵的可能性不大.     

短期夜间低温后番茄光合作用及叶绿体超微结构的恢复效应

为明确短期夜间低温后番茄光合作用在常温下的恢复效应,研究了番茄幼苗经夜间15 ℃（对照）、12 ℃、9 ℃和6 ℃处理7 d后植株光合作用和叶绿体超微结构的变化.结果表明：短期夜间低温处理有利于恢复期番茄叶片的光合作用;12 ℃和9 ℃处理叶片叶绿素含量均可恢复至对照水平,6 ℃处理叶绿素含量则不可恢复;夜间低温处理并未严重抑制叶片气孔的形成,相反刺激了恢复期叶片气孔的形成与发育;6 ℃处理后叶绿体基粒片层排列较松散,片层数减少.恢复7 d时,夜间处理温度越低,叶绿体中淀粉粒越小、数量越少,基粒片层排列越整齐致密.另外,短期夜间低温处理促进了番茄植株叶片在恢复期的光合产物运输.     

引种红树与中国乡土红树幼苗光合特性研究

用Li-COR 6400便携式光合作用测定系统对海南东寨港自然保护区人工育苗的中国乡土红树--海桑、引种红树--无瓣海桑和拉关木幼苗光合特性进行比较研究.结果显示:(1)无瓣海桑和拉关木叶片净光合速率日变化呈双峰曲线,最高峰出现在12:00,次高峰出现在15:00,而海桑呈现单峰曲线,峰值出现在12:00左右;无瓣海桑和拉关木叶片净光合速率的峰值均高于海桑.(2)3种红树叶片净光合速率和蒸腾速率的峰值均在同一时间(12:00)出现;胞间CO2浓度不随气孔导度的降低而减小,控制红树幼苗光合速率因子为非气孔限制;拉关木叶片水分利用效率要低于无瓣海桑和海桑.(3)与海桑幼苗相比,引种的无瓣海桑和拉关木幼苗的光补偿点和光饱和点均较低,而其表观量子效率较高,其光饱和净光合速率(Pmax) 较大,且其CO2补偿点较低,CO2利用率较高,强光下的光合能力高.研究表明,无瓣海桑比海桑和拉关木具有更好的低光适应能力;拉关木有着较高的光合同化能力,其幼苗对生境的适应能力高于海桑属植物.     

Cold nights impair leaf growth and cell cycle progression in maize through transcriptional changes of cell cycle genes

Low temperature inhibits the growth of maize (Zea mays) seedlings and limits yield under field conditions. To study the mechanism of cold-induced growth retardation, we exposed maize B73 seedlings to low night temperature (25 degrees C /4 degrees C, day/night) from germination until the completion of leaf 4 expansion. This treatment resulted in a 20% reduction in final leaf size compared to control conditions (25 degrees C/18 degrees C, day/night). A kinematic analysis of leaf growth rates in control and cold-treated leaves during daytime showed that cold nights affected both cell cycle time (+65%) and cell production (-22%). In contrast, the size of mature epidermal cells was unaffected. To analyze the effect on cell cycle progression at the molecular level, we identified through a bioinformatics approach a set of 43 cell cycle genes and analyzed their expression in proliferating, expanding, and mature cells of leaves exposed to either control or cold nights. This analysis showed that: (1) the majority of cell cycle genes had a consistent proliferation-specific expression pattern; and (2) the increased cell cycle time in the basal meristem of leaves exposed to cold nights was associated with differential expression of cell cycle inhibitors and with the concomitant down-regulation of positive regulators of cell division.     

2008年南方低温对我国红树植物的破坏作用

2008年初, 我国南方19个省经历了50年一遇的持续低温雨雪冰冻天气。极端气候对华南沿海各省的红树林区造成不同程度的危害。2008年3月, 在我国南方各省红树林区的10个代表性地点, 对这次寒害造成的红树植物伤害程度进行了系统的调查。结果表明: 冬季低温对红树林的影响极为显著, 特别是在低纬度的海南、广西和广东湛江, 由于极端低温正值夜间退潮, 对红树林的影响更为显著; 在纬度较高的福建, 本地红树种类秋茄(Kandelia obovata)、桐花树(Aegiceras corniculatum)和白骨壤(Avicennia marina)及引种的木榄(Bruguiera gymnorrhiza)等, 由于长期适应于冬季较低的气温或在种植前经过抗寒锻炼, 具有较强的抗寒能力。各地主要红树植物中, 广布种秋茄、桐花树和白骨壤最为耐寒, 其耐寒性均大于红树科的木榄、海莲(Bruguiera sexangula)和红海榄(Rhizophora stylosa)。海桑(Sonneratia caseolaris)对温度的敏感性最强, 抗寒能力最低, 因此, 即使在其原产地海南也受到较为严重的寒害, 在纬度更高的引种地出现大面积受害甚至全部死亡, 而从孟加拉国引种的无瓣海桑(Sonneratia apetala)却显示出一定的抗寒能力。同一地点的红树植物幼苗的抗寒能力低于大树。此次寒害也造成了苗圃场的种苗大量死亡, 成熟的植株提前落花落果, 这势必会影响后继一两年内红树林的自然更新和人工造林。因此, 在未来红树林造林或人工引种中, 一定要考虑到红树植物的抗寒能力。     

Effect of flooding and temperature regime on growth and stomatal resistance ofBetula platyphylla var.japonica seedlings

Summary Both flooding and low temperature reduced height and stem diameter growth; leaf initiation; growth of leaves, stems, and roots; and lowered root-shoot ratios of 112-dayoldBetula platyphylla var.japonica seedlings. Flooding also induced leaf scorching and abscission. Growth was reduced much more by flooding than by low temperature. Interactive effects of flooding and temperature were shown on height growth, leaf initiation and expansion, and dry weight increment of leaves, stems and roots. The amount of growth reduction by flooding and low temperature was greater when based on analysis of dry weight increment of leaves, stems, and roots, than on their relative growth rates. The greater reduction of growth by flooding than by low temperature was associated with fewer and smaller leaves, more leaf injury, more stomatal closure, and greater decay of roots in flooded plants. Flooding and low temperature appeared to reduce growth by somewhat different physiological mechanisms. Research supported by the College of Agricultural and Life Sciences, University of Wisconsin, Madison, WI, USA and by Yamagata University, Tsuruoka, Japan. McIntyre-Stennis Project 2599.     

LEAF SURFACE WETNESS AND GAS EXCHANGE IN THE POND LILY NUPHAR POLYSEPALUM (NYMPHAEACEAE)

As part of a continuing study of the effects of leaf surface wetness on gas exchange, the occurrence of leaf surface wetting by dewfall and associated effects on photosynthesis were evaluated for floating and aerial leaves of the pond lily Nuphar polysepalum Engelm. Because of nighttime radiation exchange with a cold sky, high humidity, and the presence of adaxial stomata, we predicted that pond lily leaves would be particularly susceptible to wetting events such as dewfall. A substantial reduction in net photosynthesis (up to 20%) occurred for leaves that were experimentally misted to simulate leaf wetting by dewfall. Aerial leaves remained below dewpoint temperatures for long periods on clear nights. However, floating leaves rarely approached dewpoint temperatures at night because minimum nighttime temperatures of leaves were up to 10 C warmer than air temperature. Thus, floating leaves of N. polysepalum did not experience dew formation primarily because of strong thermal coupling to a substrate (water) that was much warmer than air temperature at night. This coupling to a warmer substrate prevented a potentially strong inhibition of photosynthetic CO₂ exchange the following morning.     

MICROCLIMATIC EFFECTS ON WATER RELATIONS,LEAF TEMPERATURES,AND THE DISTRIBUTION OF HERACLEUM LANATUM AT HIGH ELEVATIONS

The small-scale distribution of an understory herb, Heracleum lanatum, was evaluated in terms of leaf temperature and water relations limitations due to a large leaf size (630 cm²). Diurnal variations in transpiration (4 to 60 mg m⁻² s⁻¹) were influenced by fluctuations in solar irradiance, wind speed, leaf temperature and stomatal conductance. Computer simulations indicated that leaf temperatures in a forest clearing would be > 12 C above air temperature, with maximum transpiration rates of 140 mg m⁻² s⁻¹, and daily water loss to be over 200% greater than values at natural understory locations. Simulations of nocturnal temperature relations indicated ~100 W m ⁻² less incident longwave irradiance in the forest clearing as compared to the understory (560 vs. 660 W m⁻² at 400 hr). This difference led to predicted leaf temperatures being as low as 6 C below air temperature in the forest clearing while measured leaf temperatures in the forest understory were within 1.5 C of air temperature throughout the night. Furthermore, minimum air temperatures were at or below 6 C on 36% of the nights during the summer growth period indicating that in open areas leaves of H. lanatum would frequently be below 0 C and subject to possible freeze damage. Heracleum lanatum may be more abundant in the shaded understory of the subalpine forest because exposure in open environments would result in high leaf temperatures and increased transpirational water loss during the day, as well as low leaf temperatures with the possibility of freeze damage at night.     

Structural and functional plasticity of<Emphasis Type="Italic"> Quercus ilex</Emphasis> seedlings of different provenances in Italy

Functional and structural leaf traits of Quercus ilex seedlings originated from parent plant acorns from three different localities in Italy were studied. Acorns from three different localities along a gradient from the north to the south of Italy: Nago (site A) in the Garda Lake region at the northernmost limit of holm oak distribution area in Italy, Castelporziano near Rome (site B), at the centre of the distribution area, and Frassanito near Otranto (site C), in a drier area in the south of Italy. Morphological and anatomical leaf traits differed between the provenances with a higher leaf mass area, total leaf thickness and the ratio of palisade to mesophyll thickness in the driest provenance (C seedlings). These traits gave C seedlings a higher water use efficiency, relative water content at predawn and photosynthetic rates than the other provenances in high air temperature conditions. The smaller leaf area of A seedlings seemed to have a higher photosynthetic capacity in low air temperature conditions than B and C seedlings. Growth analysis underlined a higher shoot relative growth rate in B seedlings explaining the highest shoot length and leaf number per shoot. The plasticity index [sensu Valladares et al. (2000) Ecology 81:1925–1936] for physiological traits of the seedlings was higher than morphological and anatomical traits, but the largest differences in plasticity among ecotypes were found for morphological and anatomical traits. The ecotypes of Q. ilex studied here seemed to integrate, at leaf level, functions of growth activity, morphology and physiology related to the climate of the original provenance.     

Influence of frost on nutrient resorption during leaf senescence in a mangrove at its latitudinal limit of distribution

The latitudinal distribution of mangrove species is limited mainly by low temperature. Leaf scorch and massive leaf fall are the predominant symptoms of frost damage. Nutrient resorption during leaf senescence is an important adaptation mechanism of mangroves. Abnormal defoliation disturbs nutrient resorption. We evaluated the effects of frost on nutrient loss of mangroves and the protective effects of warmer seawater inundation on reducing nutrient loss. On January 14, 2009, the most cold-tolerant mangrove Kandelia obovata at its naturally latitudinal limit (Fuding, China, 27°17??N) was exposed to freezing temperature (?2.4°C) for 4 h (minimum ?2.8°C). The freezing air temperature occurred during flood tide, resulting that the flooded shoots were protected by warmer seawater. Frost caused 31.3% and 13.0% defoliation on the exposed shoots and the flooded shoots, respectively. Frost restricted nutrient resorption during leaf senescence. K. obovata resorbed 61% N and 42% P during normal leaf senescence, respectively. However, frost-damaged leaves only resorbed 13% N and 10% P during the course, respectively. Foliar N:P molar ratios were <31, suggesting N limitation. Tidal inundation can partially protect mangroves from frost damage. Reduced nutrient resorption efficiency and massive leaf fall caused by frost add pressure to mangroves under nutrient limitation at their latitudinal limits.     

Tidal movements of shallow water fishes in Kuwait Bay

The intertidal migrations of shallow water fishes in Kuwait Bay were studied during two 24 h periods using an otter trawl. Most species wereconcentrated at a location corresponding to Low Low Water mark. At the other tidal levels some fishes migrated with the tide to High High Water mark through a horizontal distance of up to 2 km. Any effect of day and night on the catch was masked by the effect of tidal condition.
Leiognarhus decorus (de Vis) was typically concentrated at Low Water but a proportion of the population followed the rising tide toward the shore. There was a die1 effect whichmay have been due to fish moving to shallower water at night compared with the day. Length-frequency distribution changed slightly with tidal state so that larger fish were not captured at High Water during the day. Of the fishes captured at high tide, the largest individuals of L. decorus were captured at a depth of 2.0 m deep. Solea elongata Day did not migrate with tidal fluctuations and was captured in large numbers only at Low Water. Arius tenuispinis Day was captured in shoals at or around Low Water.