广西北部湾典型海岛红树林的结构特征、空间格局及种间种内关联性

为研究广西北部湾茅尾海自然保护区海岛红树林群落的空间点格局和演替规律,在典型红树林海岛设置调查样地,以样地内的桐花树(Aegiceras corniculatum)、秋茄(Kandelia obovata)、白骨壤(Avicennia marina)等红树植物为研究对象,构建单变量函数的完全空间随机模型、异质泊松模型与双变量函数的环形转变模型,分析3种红树林种群的结构特征、空间格局及种内种间关联性。结果发现：(1)桐花树种群的小树和中树的个体数目较多,种群年龄结构呈金字塔型,种群处于增长状态;秋茄种群的中树个体数目较多,种群结构呈钟型,种群数量处于稳定状态;白骨壤个体数相对较少,且幼树较少老树较多,种群更新受阻,种群结构呈纺锤型,属于衰退型种群。(2)红树林群落整体上呈现出空间集聚的分布特征,从不同种群的集聚程度来看：桐花树>白骨壤>秋茄。(3)随着空间尺度的增大,红树林群落在空间分布上依次表现出聚集、随机和均匀3种特征。(4)桐花树与秋茄、白骨壤的种间关系随着尺度增加均表现为空间无关联性-空间负关联性-空间无关联性的演变特征,秋茄与白骨壤的种间关系则为全尺度的空间无关联性。(5)桐花树种内不同龄级之间存在空间正关联性、空间无关联性和空间负关联性,秋茄种内不同龄级之间均表现出空间无联性,白骨壤种群则在不同龄级之间均出现空间正关联性。(6)红树植物种群的空间格局受到自身繁殖特性、生境异质性、种内和种间竞争、病虫害等多种因素的影响。红树林人工种植和恢复需要结合沿海地区的自然生态条件,按照红树林种群的适应形态学特点、群落类型和自然演替规律,种植乡土红树植物,适当引进外来物种,研制出近似天然的人工红树林林分结构,提高群落的生物多样性和群落稳定性,发挥红树林湿地生态系统的生态环境效应。     

Factors regulating carbon sinks in mangrove ecosystems

Mangroves are recognized as one of the richest carbon storage systems. However, the factors regulating carbon sinks in mangrove ecosystems are still unclear, particularly in the subtropical mangroves. The biomass, production, litterfall, detrital export and decomposition of the dominant mangrove vegetation in subtropical (Kandelia obovata) and tropical (Avicennia marina) Taiwan were quantified from October 2011 to July 2014 to construct the carbon budgets. Despite the different tree species, a principal component analysis revealed the site or environmental conditions had a greater influence than the tree species on the carbon processes. For both species, the net production (NP) rates ranged from 10.86 to 27.64 Mg C ha^?1 year^?1 and were higher than the global average rate due to the high tree density. While most of the litterfall remained on the ground, a high percentage (72%–91%) of the ground litter decomposed within 1 year and fluxed out of the mangroves. However, human activities might cause a carbon flux into the mangroves and a lower NP rate. The rates of the organic carbon export and soil heterotrophic respiration were greater than the global mean values and those at other locations. Only a small percentage (3%–12%) of the NP was stored in the sediment. The carbon burial rates were much lower than the global average rate due to their faster decomposition, indicating that decomposition played a critical role in determining the burial rate in the sediment. The summation of the organic and inorganic carbon fluxes and soil heterotrophic respiration well exceeded the amount of litter decomposition, indicating an additional source of organic carbon that was unaccounted for by decomposition in the sediment. Sediment‐stable isotope analyses further suggest that the trapping of organic matter from upstream rivers or adjacent waters contributed more to the mangrove carbon sinks than the actual production of the mangrove trees.     

盐沼草—白骨壤混种减轻污损动物危害的生物防治效果研究

广西北仑河口区新造高程约220 cm 的潮间带裸滩,移植白骨壤与茳芏、沟叶结缕草、芦苇和南水葱四种盐沼草进行混种,研究盐沼草-红树混种减轻污损动物对人工红树林危害的生物防治效果。结果表明：沟叶结缕草和茳芏可快速生长和扩展,缓流、促淤能力高于长势较差的南水葱和芦苇。在盐沼和白骨壤上发现19种污损动物,其中潮间藤壶、白条地藤壶、黑口滨螺和粗糙滨螺为优势种。茳芏和沟叶结缕草受污损程度较南水葱和芦苇轻。四种盐沼草受污损程度均低于白骨壤。白骨壤＋茳芏、白骨壤＋沟叶结缕草混种均可有效减轻污损动物对白骨壤苗木危害,这两类树-草混种处理区苗木的高度、叶数、枝数、枝下高和存活率等指标均较其他处理区好。初步判断“盐沼草-红树林协同生态修复体系”对于营造人工红树林有较高应用价值。     

The relation between recalcitrancy of a mangrove plant, Kandelia obovata, and high endogenous level of abscisic acid

Kandelia obovata Sheue, Liu & Yong sp. nov. is one of the cold tolerant mangrove plants. Some callus formation was obtained from the leaves of K. obovata in liquid medium containing 10 μM of 2,4-dichlorophenoxyacetic acid. However, recalcitrancy was found when subculturing them. Endogenous levels of gibberellins (GAs) and abscisic acid (ABA) in leaf protoplasts of K. obovata were determined using micro-scale extraction and purification steps, including thin layer chromatography and quantification by micro-bioassay or enzyme linked immunosorbent assays. Very high amounts of ABA and low activities of GAs were found in leaf protoplasts of K. obovata. Low concentrations of gibberellic acid and uniconazole-P were effective of enhancing cell enlargement in protoplast cultures. Exogenous application of ABA was inhibitory to protoplast culture. All cytokinins tested were inhibitory to both leaf and protoplast cultures. The high endogenous level of ABA is most likely the underlying cause of recalcitrancy of mangrove cultures.     

Guard cell photosynthesis is critical for stomatal turgor production,yet does not directly mediate CO2‐ and ABA‐induced stomatal closing

Stomata mediate gas exchange between the inter‐cellular spaces of leaves and the atmosphere. CO₂ levels in leaves (Ci) are determined by respiration, photosynthesis, stomatal conductance and atmospheric [CO₂]. [CO₂] in leaves mediates stomatal movements. The role of guard cell photosynthesis in stomatal conductance responses is a matter of debate, and genetic approaches are needed. We have generated transgenic Arabidopsis plants that are chlorophyll‐deficient in guard cells only, expressing a constitutively active chlorophyllase in a guard cell specific enhancer trap line. Our data show that more than 90% of guard cells were chlorophyll‐deficient. Interestingly, approximately 45% of stomata had an unusual, previously not‐described, morphology of thin‐shaped chlorophyll‐less stomata. Nevertheless, stomatal size, stomatal index, plant morphology, and whole‐leaf photosynthetic parameters (PSII, qP, qN, F_V′/F_M′) were comparable with wild‐type plants. Time‐resolved intact leaf gas‐exchange analyses showed a reduction in stomatal conductance and CO₂‐assimilation rates of the transgenic plants. Normalization of CO₂ responses showed that stomata of transgenic plants respond to [CO₂] shifts. Detailed stomatal aperture measurements of normal kidney‐shaped stomata, which lack chlorophyll, showed stomatal closing responses to [CO₂] elevation and abscisic acid (ABA), while thin‐shaped stomata were continuously closed. Our present findings show that stomatal movement responses to [CO₂] and ABA are functional in guard cells that lack chlorophyll. These data suggest that guard cell CO₂ and ABA signal transduction are not directly modulated by guard cell photosynthesis/electron transport. Moreover, the finding that chlorophyll‐less stomata cause a ‘deflated’ thin‐shaped phenotype, suggests that photosynthesis in guard cells is critical for energization and guard cell turgor production.     

Processes of organic carbon in mangrove ecosystems

In addition to carbon accumulation in plants, processes of organic carbon in mangrove ecosystems include origins of sediment organic carbon, carbon fluxes between mangroves and their adjacent systems (coastal waters and atmosphere), and cycling processes. Sediment organic carbon originates from suspending solids in coastal waters, mangrove plants and benthic algae. In mangroves with low organic carbon content in sediments, tidal seawater is the main origin of sediment organic carbon, while in mangroves with high sediment organic carbon contents, sediment organic carbon mainly originates from mangrove plants. Due to tidal flush, there is large material exchange between mangrove ecosystems and their adjacent coastal waters. In China, exports of organic carbon in litter falls and dissolved organic carbon from mangroves to their adjacent coastal waters have not been documented. Processes of mangrove litter falls, including production, decomposition, export and animal consumption, determine linkages among organic carbon among mangrove plants, secondary production and coastal ocean. Consumers especially benthic animals may influence organic carbon in mangrove ecosystems, because (1) their consumption rates are high, and their selective feeding on some food sources will change the relative quantities of export, bury and mineralization of organic carbon from different origins; (2) their consumption is much more than assimilation, resulting in the changes in sizes, forms and qualities of non-assimilated organic matters, and then the changes in availability of export, consumption or mineralization of organic carbon. Respiration and sulfate reduction are important mineralization processes of organic carbon in mangrove sediments. Mineralization rates of organic carbon in mangrove sediments are influenced by quantities, activities and particle sizes of organic matters, and other factors such as forest ages, root activities and animal burrowing activities. Researches on processes of mangrove organic carbon should be based on open systems, and ecological processes of organic carbon should be coupled with vegetation restoration.     

Processes of organic carbon in mangrove ecosystems

In addition to carbon accumulation in plants, processes of organic carbon in mangrove ecosystems include origins of sediment organic carbon, carbon fluxes between mangroves and their adjacent systems (coastal waters and atmosphere), and cycling processes. Sediment organic carbon originates from suspending solids in coastal waters, mangrove plants and benthic algae. In mangroves with low organic carbon content in sediments, tidal seawater is the main origin of sediment organic carbon, while in mangroves with high sediment organic carbon contents, sediment organic carbon mainly originates from mangrove plants. Due to tidal flush, there is large material exchange between mangrove ecosystems and their adjacent coastal waters. In China, exports of organic carbon in litter falls and dissolved organic carbon from mangroves to their adjacent coastal waters have not been documented. Processes of mangrove litter falls, including production, decomposition, export and animal consumption, determine linkages among organic carbon among mangrove plants, secondary production and coastal ocean. Consumers especially benthic animals may influence organic carbon in mangrove ecosystems, because (1) their consumption rates are high, and their selective feeding on some food sources will change the relative quantities of export, bury and mineralization of organic carbon from different origins; (2) their consumption is much more than assimilation, resulting in the changes in sizes, forms and qualities of non-assimilated organic matters, and then the changes in availability of export, consumption or mineralization of organic carbon. Respiration and sulfate reduction are important mineralization processes of organic carbon in mangrove sediments. Mineralization rates of organic carbon in mangrove sediments are influenced by quantities, activities and particle sizes of organic matters, and other factors such as forest ages, root activities and animal burrowing activities. Researches on processes of mangrove organic carbon should be based on open systems, and ecological processes of organic carbon should be coupled with vegetation restoration.     

Effect of an integrated mangrove-aquaculture system on aquacultural health

Mangroves are unique intertidal halophyte formations growing in sheltered tropical and subtropical coastal areas. Due to the increasing population and economic development, mangroves have faced degradation and loss, which has been mainly caused by land conversion into aquaculture ponds in Asia. In the past several decades, the rapid growth of aquaculture has induced water pollution. Using mangroves for effluent treatment from coastal aquaculture ponds could be a suitable approach for wastewater treatment and healthy aquaculture development. An Integrated Mangrove-Aquaculture System (IMAS) was established to test whether the idea of a mangrove in situ treatment for aquaculture wastewater is feasible. The monocultures of three mangroves, Sonneratia caseolaris, Kandelia obovata, and Aegiceras corniculatum were established with area proportions of 45%, 30%, or 15%, respectively. One control pond without mangroves was also set up. The results indicated that the mangroves had different tolerabilities to long-term inundation. The aquaculture ponds had different fishery yields, considering the mangrove species and area proportions. The water quality of most of the experimental ponds was better than the control pond, except for the planted Sonneratia. It is concluded that mangroves can reduce the concentration of dissolved inorganic nitrogen and phosphate, buffer the pH value and increase the concertration of dissolved oxygen in aquaculture water bodies effectively. It is suggested to use 15% of the Aegiceras corniculatum area to conduct in situ purification of aquaculture wastewater and to enhance aquaculture production.     

Development of a salinity-secondary flow-approach model to predict mangrove spreading

This paper presents a new salinity-secondary flow-approach (SSA) model for identifying areas likely to be colonized by mangrove species based on two indices: water salinity concentration and river secondary flow intensity, R/W (the ratio of radius of curvature to river width). The mangrove Kandelia obovata is spreading rapidly in the Tanshui River system and therefore resulting in flooding impact to riparian wetlands; however, few studies have examined the dispersal characteristics of this species on the reach scale. According to the literature review and our observation, the salinity is the major factor in determining the spreading capabilities of mangroves. In addition, the effect of secondary flow can also facilitate mangrove invasion through the creation of bare mudflats.The case study of the Tanshui River system shows that the SSA model can be used for the determination of the habitat requirements and thus the dispersal capabilities of K. obovata. The results of the study show that the optimum conditions for the growth and dispersal of K. obovata exist in waters with mean annual salinity levels that are higher than 5 ppt (parts per thousand). Although K. obovata can survive in brackish wetlands with mean annual salinity levels lower than 5 ppt, its spreading capability is impaired. In tidal freshwater wetlands with mean annual salinity levels that are lower than 0.1 ppt, K. obovata cannot survive. The study also found that the R/W lower than 3 led to large mudflats, which provide an ideal environment for the growth of mangroves, due to the secondary flow.It shows that the SSA model can identify the potential habitat of mangrove in tidal region, so it might help with not only estuarine wetland management but also mangrove restoration project, especially for the sea level rise effect and its impact on potential mangrove invasion.     

Restoration of Shorebird‐Roosting Mudflats by Partial Removal of Estuarine Mangroves in Northern Taiwan

Expansion of the monospecific mangrove, Kandelia obovata, has converted intertidal mudflats and other habitats into mangrove forests, thus reducing estuarine biodiversity in the Danshuei River estuary, northern Taiwan. Dense mangrove vegetation was removed to create a small patchwork of mudflats and a tidal creek in February 2007. Subsequent changes in sediment properties and biodiversity of the macrobenthos and avian communities were examined. The results showed that the creation of different habitats led to changes in sediment properties and biodiversity. The water content and sorting degree of the sediments differed significantly among the restored mudflat, the tidal creek, and the mangrove control site. Silt/clay, organic carbon content, and chlorophyll a concentrations varied seasonally, but not among sites. The abundance of polychaetes in the creek was greater than that in the mudflat or the mangrove (12.5 vs. 5.3 and 2.2 individuals/m², respectively), suggesting preferential colonization of infaunal polychaetes in habitats with prolonged submersion. Crabs showed seasonal changes in density, with higher densities in summer than in autumn and winter. The species richness of wintering shorebirds on the created mudflat increased dramatically from 2002 to 2007. The transformation of a vegetated area into an open mudflat appeared to benefit shorebirds by providing roosting habitat. Our study demonstrated that controlling the spread of estuarine mangrove forests could increase biodiversity, and could particularly benefit the migratory shorebird community.     

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.     

A novel microsatellite locus isolated from an AFLP fragment in the mangrove species Kandelia obovata (Rhizophoraceae)

The study of AFLP analysis in Kandelia obovata, one of the major mangrove species in Japan, revealed the existence of a unique fragment showing stuttered peaks. We cloned this fragment and found a novel microsatellite locus. We report the method used for isolation and the polymorphic nature of this locus among the populations on Iriomote Island.     

Chlorophyll formation and the development of photosynthesis in illuminated etiolated pea leaves

Summary The protein synthesis inhibitors chloramphenicol and terramycin, and light of low intensity were used to retard the rate of chlorophyll formation in illuminated dark grown pea leaves. In the control leaves the onset of photosynthesis, as measured by carbon dioxide exchange of the whole leaves, and reduction of ferricyanide and metmyoglobin and photo-oxidation of ascorbate in isolated chloroplasts, was observed after 2–4 hours illumination. The photosynthetic activity of the treated leaves did not commence until 10–12 hours illumination had elapsed. In both the control and treated leaves the onset of photosynthesis occurred when the total chlorophyll content was 0.04 mg/g fresh weight. The precise point of photosynthetic inception was apparently more related to the attainment of a specific total chlorophyl content than to the ratio of chlorophyll a to chlorophyll b. A marked increase in the evolution of carbon dioxide in the light was observed in the treated leaves during the first 10 hours of greening. This observation could not be ascribed to photorespiration since the leaves did not possess an active photosystem. It is suggested that the enhanced respiration may have been due to the light-induced activation of synthetic pathways responsible for the formation of chloroplast constituents.The following abbreviations are used CMU 3(3-chlorophenyl)-1, 1-dimethylurea - DCIP dichlorophenol indophenol - PMS phenazine methosulphate - TRIS 2-amino-2-hydroxymethyl propane-1, 3-diol This work was supported by a Science Research Council studentship granted to R. J. Dowdell and submitted for the degree of Ph. D. of Bath University of Technology.     

Status and exploitation of the mangrove and associated fishery resources in Zanzibar

The distribution and growth forms of the mangroves on Zanzibar island (Unguja and Pemba) were investigated. Pemba island, with approximately 12000 ha of mangroves, had nine species; and Unguja island, with 6 000 ha, had eight. Average cropping intensities in Pemba island varied between 350–1937 cut plants per ha while in Unguja these were between 777–3567 cut plants per ha. In Pemba, mangrove forests were relatively less heavily exploited compared to those in Unguja, where clear felling was common. Charcoal, lime and salt production are the major activities which involve heavy utilization of mangrove wood.The fishery resources (shellfish and finfish) associated with the mangrove vegetation were also investigated by examining the composition of fish catches at landing stations in mangrove as well as nonmangrove zones of fishing districts. A survey on the fauna associated with mangrove forests was also conducted. A number of the local commercial fish species were found to be associated with the mangrove vegetation. The fishes of the genusLethrinus and the rabbit fishSiganus were found to constitute the bulk of the fish caught from waters adjacent to mangroves using movable traps. The molluscPyrazus sp., which is commonly used by the local people for food and bait, was found only in the mangroves.     

两种红树叶的几种酶的生理特性与海滩盐度的相关性初探

本文是福建九龙江口红树林研究的一部分,主要讨论两种红树植物(秋茄,桐花树)叶片中的几种酶对海滩盐度(3—12‰范围内)变化的反应,测定结果如下：1,桐花树叶片过氧化物酶同工酶和细胞色素氧化酶同工酶的含量对土壤盐度变化的反应表明：土壤盐度(3—12‰)提高,过氧化物酶和细胞色素氧化酶同工酶的谱带加深、加宽,而且谱带中出现新酶带。 2．当海滩盐度提高时,桐花树叶片的过氧化物酶的活性提高,秋茄叶片的乙醇酸氧化酶的活性减弱。 3．两种红树植物叶绿素含量与土壤盐度相关性显示出：当土壤盐度在3—8‰范围时,叶绿素含量变化不大;8—10‰时有一个高峰,大于10‰时又下降。可能红树植物对海滩盐度适应有一个临界值。     

Comparative systematic study of colleters and stipules of Rhizophoraceae with implications for adaptation to challenging environments

Colleters are multicellular secretory structures found on various organs in flowering plants. Colleters on the adaxial sides of stipules have been hypothesized to play a role in protecting the developing shoot. Rhizophoraceae is a stipulate family with a broad distribution from mangrove to montane environments, which makes the family well suited for the examination of this hypothesis, but the colleters of Rhizophoraceae are not well known. We compared species from all three tribes of Rhizophoraceae, including five inland genera and all four mangrove genera. In all species, several to hundreds of colleters, sessile or stalked, arranged in rows aggregated in genus‐specific shapes, are found at the adaxial bases of open and closed stipules. Pellacalyx uniquely has additional colleters at the stipule margins. Colleters are all of the standard type, comprising a central axis of core parenchyma with large vacuoles and tannins, and an outer palisade‐like epidermis with organelles involved in secretory activity. An exception is Pellacalyx axillaris, in which colleters appear as extremely small epidermal protrusions. Kandelia obovata has a tracheary element in some colleters. Pellacalyx uniquely has an unusual fleshy outgrowth on the adaxial stipule base. We propose an evolutionary sequence in which Macarisia has plesiomorphic stipule and colleter traits and the mangrove Kandelia obovata with colleter vascular traces is most derived. Colleter and stipule structures are largely concordant with habitat and phylogeny, and show taxonomic value. The strong alignment of colleter and stipule patterns with habitat is suggestive that colleters have a protective function, although some components of these patterns may be phylogenetically determined. © 2013 The Linnean Society of London, Botanical Journal of the Linnean Society, 2013, 172 , 449–464.     

红树林恢复初期莱氏锥滨螺分布动态

树栖腹足类动物是红树林底栖动物的重要组成部分,其组成和分布受到红树植被的影响。因此,在红树林生态修复中,腹足类动物的恢复依赖于植被的发育。滨螺科(Littorinidae)锥滨螺属(Mainwaringia)动物是亚洲红树林的广布种,但针对其在红树林中的分布及种群特征的研究较少,对红树林植被恢复过程中锥滨螺属动物的恢复动态更是鲜有研究。调查了厦门下潭尾湿地秋茄(Kandelia obovata)红树林恢复初期,新记录种莱氏锥滨螺(Mainwaringia leithii)种群恢复的时间动态,并分析其与植被参数的关系。研究发现,红树林恢复初期,秋茄植被生长迅速,株高、冠幅、基径和覆盖度分别由0.5年生幼林的41.3 cm、25.0 cm、1.04 cm和25%增长为8年生样地的179.2 cm、76.7 cm、5.96 cm和95%。在秋茄胚轴种植6个月左右开始记录到莱氏锥滨螺的个体,其密度和生物量在1.5 a后达到最大(分别为136个/m²和1.86 g/m²),而后逐渐降低,种植3 a后秋茄林内莱氏锥滨螺仅零星分布。除8年生的样地,莱氏锥滨...     

Comparative study of water uptake and photosynthetic gas exchange between scrub and fringe red mangroves,Rhizophora mangle L.

Summary The red mangrove (Rhizophora mangle L.) occurs frequently in both scrub and fringe mangrove forests. Our previous study demonstrated that individuals of this mangrove species growing in scrub and fringe forests differ significantly in both morphological and physiological characteristics. To further characterize physiological differences between scrub and fringe mangroves, we compared their differences in water uptake and photosynthetic gas exchange during different seasons. In the wet season (June–October, 1990), scrub mangroves showed lower D and ¹⁸O values of stem water than fringe mangroves, indicating more usage of rain-derived freshwater. In the dry season (Jan–April, 1991), however, scrub mangroves utilized the same water source as fringe mangroves, reflected by their similar D and ¹⁸O values of stem water. Consistently, there were significant differences in predawn water potentials between scrub and fringe mangroves in the wet season (October 1990) with higher values for scrub mangroves, but no significant differences in the dry season (January 1991). Higher elevation in the scrub forest seems to be the major factor responsible for the shift of water sources in scrub mangroves. On Apr. 27 and Aug. 8, 1990, scrub mangroves showed lower CO₂ assimilation rate, stomatal conductance, and intercellular CO₂ concentration than fringe mangroves. There were no differences in these gas exchange characteristics on the other two measuring dates: Oct. 17, 1990 and Jan. 11, 1991. Instantaneous water use efficiency was significantly higher for scrub mangroves than for fringe mangroves on three of the four sampling dates. Similarly, leaf carbon isotope discrimination of scrub mangroves was always significantly lower than that of fringe mangroves, indicating higher long-term water use efficiency. Higher water use efficiency in scrub mangroves is a result of stomatal limitation on photosynthesis, which may entail considerable carbon cost to the plants.     

Leaf anatomy and photosynthetic efficiency of <Emphasis Type="Italic">Acrostichum danaeifolium</Emphasis> after UV radiation

This paper reports effects of ultraviolet B (UVB) radiation on leaf anatomy and contents of chlorophyll and carotenoids, as well as photosynthetic parameters, in young sporophytes of Acrostichum danaeifolium Langsd. & Fisch. (Polypodiopsida, Pteridaceae) exposed to UV radiation treatments for 1 h daily for six weeks. The leaves showed large aerenchyma and present chloroplasts in both epidermises. After cultivation under PAR + UVA + UVB, leaves showed curling and malformed stomata on the abaxial face. After the UV treatment, chloroplasts in leaves were arranged against the inner wall of the epidermal cells. Transmission electron microscopy analysis showed some dilated thylakoids and plastoglobuli in chloroplasts and vesicles containing phenolic compounds in the cytoplasm. Differences were not observed between control and UV-treated plants in their contents of chlorophylls, carotenoids, and photosynthetic parameters. A. danaeifolium grown in sunny mangrove environment seems to have mechanisms preventing photosystem damage.     

Stomatal aperture,photosythesis and water fluxes in mesophyll cells as affected by the abscission of leaves. Simultaneous measurements of gas exchange,light scattering and chlorphyll fluorescence

Carbon dioxide exchange, transpiration, chlorophyll fluorescence and light scattering of leaves of Lycopersicom esculentum, Helianthus annuus and Arbutus unedo were measured simultaneously before and after abscission of leaves. Scattering of a weak green measuring beam was used to monitor water fluxes across the thylakoid membranes of the mesophyll. When leaves were cut under water, stomata initially closed partially and then occasionally exhibited distinct regulatory oscillations. As stomata closed, light scattering decreased indicating water influx into the mesophyll. Stomatal oscillations were accompanied, with small but noticeable phase shifts, by oscillations of water fluxes at the thylakoid level. These fluxes could be distinguished from the water fluxes accompanying light-dependent ion pumping across the thylakoids by the concomitant chlorophyll fluorescence signals. The latter record energy-dependent ion fluxes in addition to redox changes of the electron-transport chain. As stomata closed partially after cutting a leaf under water, photosynthesis decreased. In Arbutus unedo and Helianthus annuus leaves, transient stomatal closure was insufficient to account for transient inhibition of photosynthesis which appeared to be brought about by transfer of an inhibitory solute through the petiole into the mesophyll. This solute also stimulated respiration in the dark. When leaves were cut in air, stomata opened transiently (Iwanoff effect) before wilting enforced closure. Photosynthesis followed the stomatal responses, increasing during opening and decreasing during closure.Dedicated to Professor H. Ullrich on the occasion of his 85th birthday