Micropropagation of grey mangrove Avicennia marina

This study was conducted to develop a micropropagation protocol for grey mangrove, Avicennia marina (Forsk.)     

Ecophysiological differences between fringe and dwarf Avicennia marina mangroves

In this investigation, morphological and physiological differences between fringe and dwarf Avicennia marina (Forsk.) Vierh. growing in seawater and hypersalinity were compared along a tree height and productivity gradient in Richards Bay, South Africa. Dwarf trees had thicker leaves and cuticles, lower specific leaf area and salt gland frequency, while the concentrations of total chlorophyll and chlorophylls a and b were lower by 26, 23 and 39%, respectively, compared to fringe trees. Soil ψ and soil salinity were −3.04 ± 0.09 MPa and 36 ± 3 psu in the fringe zone, compared to −7.24 ± 0.38 MPa and 58 ± 5 psu, respectively, in the dwarf zone. Midday minimum xylem ψ was −4.3 ± 0.23 MPa in the fringe zone and −6.4 ± 0.28 MPa in the dwarf zone. In leaves of dwarf trees, the concentration of Na⁺ was 30% higher, while those of K⁺, Ca²⁺ and Mg²⁺ were lower by 41, 38 and 55%, respectively, than fringe trees. The Na⁺/K⁺ ratio of leaves was 2.1 ± 0.03 for fringe and 5.6 ± 0.05 for dwarf trees. Rates of secretion of Na⁺, Cl⁻, K⁺, Ca²⁺ and Mg²⁺ over 24 h were significantly lower in dwarf trees by 44, 45, 78, 66 and 54%, respectively. In fringe trees, the rate of secretion of Na⁺ and Cl⁻ was about 28% higher during the night than during the day, while in dwarf trees the corresponding increase was about 174%. CO₂ exchange, leaf conductance, quantum yield of PS II, ETR through PSII and intrinsic photochemical efficiency of PS II were significantly lower in dwarf trees by 50, 83, 39, 33 and 12%, respectively.     

Salinity, growth and root respiration in the grey mangrove, Avicennia marina

Relationships between growth parameters and root respiration under various conditions of salinity were investigated in seedlings of the grey mangrove Avicennia marina (Forsk.) Vierh. Growth, root/shoot ratios, leaf succulence and osmotic potential of leaves were measured for seedlings grown for 6–8 weeks in 100, 50, 25 and 0% seawater. Oxygen uptake of root segments, from distal to proximal ends of roots, was measured for all treatments. Total growth was maximal in 25% seawater, highest leaf succulence was obtained in 50% seawater, and highest leaf osmotic potential in 100% seawater. Oxygen uptake in distal root segments, as measured both by Clark oxygen electrode and Warburg manometry, showed a stimulation in the presence of salt that closely paralleled growth stimulation. The rates of respiration were highest in 25% seawater. The oxygen uptake was not stimulated by salt per se, since concentrations higher than 25% were associated with a decline in rate of oxygen uptake from the maximum. Values for the respiratory quotient approximated to one in all treatments. Avicennia marina has been reported to exclude from its roots about 90% of the salt in the surrounding medium. It might have been expected that increased concentrations of salt in the growth medium would be associated with a standard salt respiration response in the roots; however, this was not obtained.     

Nutrient-use efficiency in arid-zone forests of the mangroves Rhizophora stylosa and Avicennia marina

Nutrient-use efficiency (NUE) within forests of the mangroves Rhizophora stylosa and Avicennia marina was estimated in arid Western Australia using litter fall rates and rates of leaf CO₂ exchange. Litter fall rates ranged from 9.8 to 34.4 t DW ha⁻¹ y⁻¹ but equated to only 13–41% (mean = 30%) of net canopy primary production. Foliar N:P ratios were in most instances ≥16, suggesting P limitation. NUE for N based on litter fall rates were significantly less (NUE_L = 167–322 g DW g⁻¹ N) than those based on photosynthesis measurements (NUE_P = 234–448 g DW g⁻¹ N), suggesting that NUE estimates for nitrogen based on litter fall data are underestimates. NUE_P estimates for N were significantly greater for R. stylosa than for A. marina. NUE for P were not significantly different, with NUE_L ranging from 2905 to 5053 g DW g⁻¹ P and NUE_P ranging from 1632 to 4992 g DW g⁻¹ P. Both sets of NUE are at the higher end of the range of estimates calculated for most other forests and equivalent to those for wet tropical mangroves. These arid-zone trees live in low-nutrient habitats, but it appears that selection on components of NUE (i.e. traits that reduce nutrient loss) rather than on NUE itself equates to a lack of clear patterns in NUE between different environments, emphasizing the flexible nature of nutrient allocation in woody plants. NUE in R. stylosa correlated inversely with mature leaf N and P content, implying that NUE in this species is maximized by the synthesis of low-nutrient leaves, i.e. a nutrient retention strategy, whereas such does not appear to be the case for A. marina. This strategy translates into a direct advantage in terms of net primary productivity for R. stylosa. This idea is supported by evidence of longer nutrient residence times for R. stylosa than for A. marina.     

Predispersal mortality and fecundity in the grey mangrove (Avicennia marina) in southeastern Australia

Abstract The predispersal mortality of floral buds and fruits in the grey mangrove (Avicennia marina) was examined over a range of populations for 3 years. The average survival of floral buds to anthesis was 34%. Moth larvae (subtribe Phycitina) attack and consume the contents of variable numbers of flower buds, but their activities did not influence bud survival, as experimental exclusion of larvae did not increase the number of buds surviving to anthesis. Fruit mortality is initially high with an average of 21% of floral buds surviving to immature fruit. Subsequent mortality is lower until on average 2.9% of floral buds survive to become viable propagules. Several cohorts of the phycitine moth larvae feed throughout the development of the fruit, and up to 62% of mature fruit show signs of larval attack. Experimental exclusion of moth larvae doubled the survival of fruits. However more than 75% of fruit mortality may be attributed to maternal regulation. Hail storms can also cause fruit mortality. The potential fecundity (number of ovules) of A. marina was measured over a range of age-size classes of trees and the realized fecundity (viable propagules) was estimated from average predispersal mortality. These estimates were subsequently verified in the field. A fecundity schedule was constructed with assumptions on reproductive frequency and reproductive life. The average annual supply of propagules over a lifetime is estimated to be about 247 viable propagules per tree.     

Zinc distribution and excretion in the leaves of the grey mangrove,Avicennia marina (Forsk.) Vierh

Mangroves are important as primary producers in estuarine food chains. Zinc is often a major anthropogenic contaminant in estuarine ecosystems and has potential ecotoxicological consequences for mangrove communities. Accumulation, distribution and excretion of zinc in the leaf tissue of the grey mangrove, Avicennia marina was studied using SEM X-ray microanalysis and Atomic Absorption Spectroscopy. The first leaves of A. marina grown in 500 μg Zn as ZnCl₂ per g of dry soil were found to accumulate 106.3±18.5 μg Zn per g dry tissue, significantly higher than control plants, after a 7-month period. Washings from first leaves contained significantly higher amounts of zinc (0.30±0.14 μg/cm² Zn) than control plants after 1 month, suggesting excretion of zinc from glandular trichomes. SEM X-ray microanalysis revealed salt crystals exuded from glandular tissue on the adaxial surface of first leaves to be composed of alkaline metals and zinc in zinc treated plants. SEM X-ray microanalysis of seedlings dosed with 4 g/l Zn as Zn Cl₂ revealed a decreasing Zn gradient from xylem tissue, through photosynthetic mesophyll, to hypodermal (water) tissue. A subsequent increase in Zn concentration was observed in glandular tissue. Cell wall Zn concentrations were consistently higher than intracellular Zn concentrations.     

中国北部湾白骨壤红树林的虫害与研究对策

危害北部湾白骨壤的主要害虫是广州小斑螟 (Oligochroacantonella)幼虫、双纹白草螟 (Pseudcatharylladuplicella)幼虫和广翅蜡蝉 (Euricaniasp.)成虫。广州小斑螟喜食害白骨壤叶片 ,造成大量叶片的枯干和枝条的死亡 ,最高可导致林木 73 %的叶面积危害。室内培养发现广大腿小蜂 (Brachymeriasp .)、啮小蜂 (Tetrastichussp .)可寄生广州小斑螟的蛹 ,终止其羽化过程。虫害具有突发性、专一性、快速扩展的特点。海水淹没可明显抑制虫害。讨论了虫害的发源、爆发的原因、生态效应和防治途径 ,并指出深入研究的方向     

Local positive feedback and the persistence and recovery of fringe Avicennia marina (Forssk.) vierh. mangroves

While mangrove restoration efforts are reasonably successful, failure often occurs in high wave energy situations. Due to differences in wave energy, seedling mortality rates vary strongly with position on the intertidal flat between high water spring and high water neap elevations. However, a local positive feedback can be present between the pneumatophores of adult mangroves and the survival of mangrove seedlings to trigger recovery. In this study, a mangrove population of Avicennia marina is modelled to determine the effects of seedling mortality and local positive feedback on mangrove recovery. The model uses life history data and dispersal to simulate population dynamics. The mangrove range limits are determined by high water spring and high water neap levels. The results indicate that within these limits mangrove populations with life-history parameter values as derived from literature are indeed capable of fast growth under conditions with low seedling mortality. Local positive feedback has then a small positive influence on population recovery after mangrove loss. If, however, mortality rates increase, such as in high wave energy situations, the importance of a positive feedback increases. The model shows that a positive feedback may, given high seedling mortality rates, be an important factor for mangrove recovery. While a positive feedback may enable mangrove persistence in unfavourable conditions, destruction of adult mangroves can remove the positive feedback, which would render the system uninhabitable and practically prohibits reforestation of such areas. The model results and the presence of positive feedbacks and their importance for population dynamics in harsh conditions indicate that investigating and understanding possible feedbacks could be crucial for successful restoration efforts.     

Ecological Wood Anatomy of Avicennia marina

The soil physicochemical indexes including edaphic pH values, edaphic salinity and soil nutrient indexes were determined in 8 Avicennia marina populations located in national nature reserve of Shenzhen of Guangzhou Province. The morphological characters in secondary xylem of Amarina populations corresponding to soil sampling which represented different habitats were surveyed by means of light microscopy and electronic microscopy. Some common specialized wood structures in Amarina growing in different habitais can be observed which suggest they function as safely conducting water under high negative pressure and are thus adaptive to intertidal habitats．These characteristics include the occurrence of: (1) some fibriform vessel elements; (2) vessel vestures and helical structures on vessel walls; (3) parenchyma cells contain lots of starch grains;(4) included phloem. Soil organic matter and soil total salt have significant effect on quantitative wood anatomical features by the stepwise regression analysis.With the increase of soil salinity and soil organic matter content which suggest occurrence of more and more serious “physiological drought”, Amarina is characterized by a higher porosity.and double thickness of vessel wall making contact with an adjacent vessel. The trends inferred that variations in the quantitative wood anatomical features of Amarina growing at different sites are adaptive to heterogenous habitats in the intertidal areas.     

Ventilation and respiration in roots of one-year-old seedlings of grey mangrove Avicennia marina (Forsk.) Vierh.

Avicennia marina (Forsk.) Vierh. was grown from seed for 12 months in artificially tidal tanks providing a range of duration and depth of inundation. Plant growth characteristics were measured at harvest. Root aerenchyma development was estimated by pycnometry, root respiration rates by manometry, and the oxygen supply capacity of the above-ground portions of the plant was determined using oxygen electrode chambers. The mass per plant at harvest was influenced by the extent of inundation during growth with maximal growth at intermediate-length (1.5 to 6.5 h per tide) inundation periods. Those plants that had been submerged the longest (8.5 h per tide) had the least root tissue. The oxygen conductance of the stem base plus any pneumatophores showed a maximum in plants grown under intermediate inundation. Oxygen demand and internal gas space per unit dry weight of root were independent of extent of inundation. During high tide the plants grown at inundation periods of more than about 3–5 hours per tide were likely to become anaerobic. This may constitute a physiological limit for this species at the bottom of the tidal range.     

Accumulation and speciation of Cd in Avicennia marina tissues

Avicennia marina is a high-Cd-tolerant species in the mangrove wetlands. A hydroponic experiment was carried out to research the accumulation and chemical form distribution of Cd in the tissues of A. marina under different concentrations and durations of Cd stress. It was found that the concentrations of Cd in plant tissues followed the order of root > stem > leaf. The data suggested that root activity decreased, Cd accumulation ability weakened in roots, and the translocation factor increased in stems and leaves with the increase of stress duration. With a proactive defense mechanism, most Cd was bound to pectates, organic acids, and protein, especially in roots and stems with the most proportion of 88.51 and 78.91%, respectively, having lower biological activities. The Cd bounded to water-soluble organic acid and free inorganic aminophenol–Cd showed the lowest concentration. The pectates, organic acids, and protein-integrated Cd seem the most important in affecting Cd detoxification for A. marina; this mechanism of change in Cd biological activities decreases the toxicity of this aggressive pollutant and presents new knowledge about the tolerance of mangrove plants.     

白骨壤幼苗的形态特征及其生物量

白骨壤1年生幼苗的株高、基径、根长、呼吸根高、叶面积以及根、茎、枝、叶、胎生苗和全株生物量等计量指标,呈现算术平均值>中值>众值组段中点的规律,符合正偏态分布节数、叶数、呼吸根数、胎生苗数等计数指标的算术平均值和中值相等,二者大于或等于众值组段中点.研究发现白骨壤1年生幼苗能生长指状呼吸根以及开花、结果和发育胎生苗,而且胎生苗成熟后直接萌发形成新的幼苗.根据实测的数据,采用一元线性回归、多元线性回归和非线性回归拟合了白骨壤1年生幼苗主要形态因子和生物量的回归模型.     

红树植物白骨壤叶片的解剖结构及其生态适应性

运用石蜡切片的方法对红树植物白骨壤的叶片进行解剖学的观察和研究。结果表明:白骨壤的叶为异面叶;上表皮为复表皮,有厚的角质膜及下皮层;下表皮上有大量的泌盐腺毛;栅栏组织多层,约占叶肉组织的2/3,海绵组织退化;机械组织和输导组织均很发达。反映了白骨壤叶片的结构与其生活的海生环境高度相适应。     

白骨壤对石油污染的生理生态响应

研究了4种不同剂量的石油处理对红树植物白骨壤的叶片叶绿素含量、过氧化氢酶活性、游离脯氨酸含量、含水量、相对电导率、根系活力与生物量、茎高和茎径生长量、存活率、萌发幼苗数、幼苗高度等生理生态指标的影响,结果表明15 0 mg剂量的伊朗轻质原油处理对白骨壤没有不利影响,30 0 mg、6 0 0 mg剂量的伊朗轻质原油处理有促进白骨壤生长的作用,12 0 0 mg剂量的伊朗轻质原油处理植株生长受到明显抑制而且出现较多的个体死亡现象。白骨壤对石油污染有较强的耐受性和适应性,但大剂量能引起植株死亡。     

Physiological Response of Avicennia marina to Salinity and Recovery

Russian Journal of Plant Physiology - In this study, the response of Avicennia marina (Forssk.) Vierh. to salinities of 0, 150, 300, 600, 900, and 1200 mM NaCl was investigated under controlled...     

The regeneration niche of the grey mangrove (Avicennia marina): effects of salinity,light and sediment factors on establishment,growth and survival in the field

Field observations of seedlings and saplings of Avicennia marina showed patterns that correlated with salinity, light and sediment. Models that account for these observations were subsequently tested in a series of field experiments. Establishment varied within an estuary under controlled conditions but was not related to salinity or sediment type. Seedling survival was uniform over 3 years regardless of position in estuary and sediment type. Seedling densities and survival under canopies or in canopy gaps were not significantly different. However, seedling growth and density of saplings were greater in canopy gaps. Experiments involving manipulations of canopies showed no differences in seedling survival under canopies or in light gaps, but addition of slow-release fertilizer enhanced growth and survival in canopy gaps and under canopies. Long-term comparison of areas denuded of a canopy and with sediment disturbance showed enhanced establishment and survival when compared with areas with canopy gaps but with undisturbed sediments. Overall there appears to be no restriction to establishment of propagules within mangrove stands other than the supply of propagules and tidal or wave action. In contrast, recruitment to the sapling stage appears to be restricted by light and sediment resources. We suggest that propagules need to establish in a regeneration niche for seedling recruitment to the sapling stage. This differs from the view that seedlings in the under-storey are analogous to a seed pool in the soil.     

Salt balance of leaves of the mangrove Avicennia marina

The contribution of each of the salt-transporting processes to the NaCl balance of the leaves of the salt-recreting mangrove Avicennia marina (Forssk.) Vierh. was quantitatively investigated. Transpiration rates, xylem sap concentration, leaf salt content, recretion rates and rates of salt retranslocation out of the leaves were continuously monitored during three day periods and the salt fluxes in and out of the leaves were calculated. The results indicated that salt filtration by the roots is by far the most important salt-rejecting mechanism, preventing some 80% of the salt which is carried towards the root surface by the transpiration stream, from entering the shoot. Out of the remaining quantity of salts which enter the root xylem and reach the leaves, only 40% is removed by the salt-recreting glands.     

The intertidal distribution of the grey mangrove (Avicennia marina) in southeastern Australia: The effects of physical conditions,interspecific competition,and predation on propagule establishment and survival

Abstract The upper and lower limits of the distribution of mature Avicennia marina lie between mean high water and mean sea level in open estuaries in southeastern Australia. Newly established seedlings are highly variable in abundance, but are rarely found in the saltmarsh or on mudflats. Their distribution is unlikely to be limited by dispersal because propagules disperse into the saltmarsh and to intertidal mudflats, but their establishment may be limited by physicochemical conditions, interspecific competition and predation. The model that physicochemical conditions control the intertidal limits of establishment of seedlings was accepted for propagules stranding in the saltmarsh but rejected for those stranding on mudflats. No seedlings established on saltmarsh sediments but similar numbers of seedlings established within light gaps in adult mangrove stands and on intertidal mudflats. The model that interspecific interaction with freeliving macroalgae (Hormosira banksii) reduces the establishment of seedlings on mudflats covered with macroalgae or in stands with a ground cover of macroalgae was accepted. Under controlled conditions five times as many propagules established on cleared ground compared with ground covered with macroalgae. Predators also reduce seedling establishment, but the model that they preferentially act on propagules stranding on the mudflat was rejected. The low number of seedlings found on mudflats without macroalgae appears to relate to wave and current effects on establishment and the effects of waterlogging or fouling on survival.     

Factors contributing to dwarfing in the mangrove Avicennia marina

BACKGROUND AND AIMS: In Richards Bay, South Africa, Avicennia marina frequently exhibits a distinct productivity gradient, with tree height decreasing markedly from 6-10 m in the fringe zone to <1.5 m in the dwarf zone which is 120 m inland at a slightly higher elevation. In this investigation, soil physico-chemical conditions between fringe and dwarf A. marina were compared and the constraints imposed by any differences on mangrove ecophysiology and productivity determined. METHODS: Soil and plant samples were analysed for inorganic ions using spectrophotometry. Gas exchange measurements were taken with an infrared gas analyser and chlorophyll fluorescence with a fluorometer. Xylem psi was determined with a pressure chamber and chlorophyll content with a chlorophyll absorbance meter. RESULTS: In the dwarf site, soil salinity, total cations, electrical conductivity and soil concentrations of Na(+), K(+), Ca(2+), Mg(2+), Zn(2+), Mn(2+) and Cu(2+) were significantly higher than those in the fringe zone. Soil water potential and the concentration of soil P, however, were significantly lower in the dwarf site. In the leaves, Na(+) was the predominant ion and its concentration was 24 % higher in dwarf than fringe mangroves. Leaf concentrations of K(+), Ca(2+), Mg(2+), Mn(2+) and P, however, were significantly lower in dwarf mangroves. Photosynthetic performance, measured by gas exchange and chlorophyll fluorescence, was significantly reduced in the dwarf plants. CONCLUSIONS: The results suggest that hydro-edaphic factors contribute to high soil salinities, low water potentials, water stress and ion imbalance within tissues including P deficiency, which in interaction, contribute to dwarfing in Avicennia marina.