Mucronata Seedlings Research Articles

Physiology and proteomics analyses reveal the response mechanisms of Rhizophora mucronata seedlings to prolonged complete submergence.

Mangrove seedlings are subject to natural tidal inundation, while occasional flooding may lead to complete submergence. Complete submergence reduces light availability and limits gas exchange, affecting several plant metabolic processes. The present study focuses on Rhizophora mucronata, a common mangrove species found along the coasts of Thailand and the Malay Peninsula. To reveal response mechanisms of R. mucronata seedlings to submergence, a physiological investigation coupled with proteomic analyses of leaf and root tissues was carried out in plants subjected to 20 days of control (drained) or submerged conditions. Submerged seedlings showed decreased photosynthetic activity, lower stomatal conductance, higher total antioxidant capacity in leaves and higher lipid peroxidation in roots than control plants. At the same time, tissue nutrient ion content displayed organ-specific responses. Proteome analysis revealed a significant change in 240 proteins in the leaves and 212 proteins in the roots. In leaves, most differentially accumulated proteins (DAPs) are associated with nucleic acids, stress response, protein transport, signal transduction, development and photosynthesis. In roots, most DAPs are associated with protein metabolic process, response to abiotic stimulus, nucleic acid metabolism and transport. Our study provides a comprehensive understanding of submergence responses in R. mucronata seedlings. The results suggest that submergence induced multifaceted stresses related to light limitation, oxidative stress and osmotic stress, but the responses are organ specific. The results revealed many candidate proteins which may be essential for survival of R. mucronata under prolonged submergence.

Growth Rate of Rhizophora Mucronata Seedlings in Coastal Areas of Central Java

Rhizophora mucronata is a type of mangrove from the Rhizophora family that can have high adaptability to an environment. The seed nursery process can be carried out by several methods, including the wetland and dry land methods. This study aims to determine the growth of mangroves. The material used in this fieldwork practice is to see how the techniques and methods of mangrove nurseries (Rhizophora mucronata) are used by the NGO Biota Foundation. The methods include preparing maintenance by embedding propagules in polybags using the wetland method in tidal areas. The results show the growth of Rhizophora mucronata mangrove from the pericarps root size, reaching 0.1 mm at four weeks.

Copper and zinc differentially affect root glutathione accumulation and phytochelatin synthase gene expression of Rhizophora mucronata seedlings: Implications for mechanisms underlying trace metal tolerance

Mangroves are susceptible to contamination due to their proximity to shores and human activities. Exposure to excessive trace metals can disturb their physiological functions and may eventually lead to death. Rhizophora mucronata is a common species growing in the mangrove forests of Thailand. Previous studies have shown that seedlings of R. mucronata are tolerant of trace metal and that they accumulate a large metal content in their root tissue. However, knowledge of their tolerance mechanisms is still lacking. To elicit the role of metal detoxification and sequestration by phytochelatins (PC) in the roots of R. mucronata seedlings, the impacts of Cu and Zn exposure were assessed on 1) physiological characteristics 2) the concentration of glutathione (GSH), a precursor of PC and 3) the level of the transcripts encoding phytochelatin synthase (PCS), the key enzyme for PC biosynthesis. Seedlings of R. mucronata were exposed to Cu and Zn in a hydroponic experiment (200 mg Cu or Zn/L in 1/4× Hoagland solution containing 8‰ NaCl, single addition). We found that both trace metals were largely accumulated in the roots. Only Cu-treated seedlings showed a decrease in the photosynthetic efficiency, in line with observed toxicity symptoms (i.e. bent stems and slight wilting of leaves). Metal accumulation, however, did not induce oxidative stress in the roots as indicated by similar level of total reactive species and lipid peroxidation across treatments. The GSH content in the roots exposed to Cu was significantly reduced while no change was observed in Zn-exposed roots. Coordinated semi-quantitative PCR and RT-qPCR revealed pcs down-regulation in Cu-treated roots, whereas Zn-treated roots showed a down-regulation on day 1 and a subsequent recovery on day 5. Failure of detoxification and sequestration of excess Cu due to GSH limitation and down-regulation of pcs may lead to the phytotoxic effects observed in Cu-treated plants. Our results suggest that both GSH and PC play an important role in trace metal tolerance in R. mucronata seedlings.

Root development in mangrove plant Rhizophora mucronata under different shade intensities

The reduced area of mangrove forests due to various pressures required rehabilitation activities throughout the damaged area of mangrove forests. Rhizophora mucronata is one of the plants in the mangrove ecosystem that has stilted roots to stand the ocean waves. It is necessary to provide R. mucronata seedlings in mangrove rehabilitation. This study aims to determine the best shade intensity for root growth of R. mucronata seedlings. This research was conducted in the nursery of Jaring Halus Village, Langkat, North Sumatra, during three months cultivation. This research used the utterly random design with five treatments, namely 0%, 25%, 50%, 75% and 100% of shading, for ten replications. The results showed that 0% shade intensity had a better growing number of primary and secondary roots and root length than the others of shade intensity. In this study, it is also estimated that the spacing planting of R. mucronata seedlings was better at 3 x 2 meters for rehabilitation activity.

Sea level rise impact on mangrove growth and development in Coral Triangle Ecoregion Southeast, Indonesia

The mangroves are among the most at-risk coastal ecosystems, which are especially vulnerable to sea-level rise. This study aimed to know the growth capacity and biochemical defense of mangrove seedlings of Rhizophora mucronata under different sea water logging at experimental condition in Kendari bay, Southeast Sulawesi, Indonesia. Results showed that maximum leaf area, intrinsic rate increase of leaf area and relative growth rate (RGR) of height of the R. mucronata seedlings were significantly higher at treatment of 45 cm from the ground than other treatments, whereas RGR of diameter was the higher at treatment of 30 cm from the ground. Meanwhile, half expansion period leaf area was almost similar for all treatment. However, the carbon and nitrogen ratio in leaves of R. mucronata seedlings was significantly higher at seawater logging of 0 cm from the ground. The flavonoid and vitamin C concentrations in R. mucronata seedlings were higher at higher level inundation indicating protective role of these compounds under seawater logging stress.

Rhizophora mucronata Lamk Seedlings Growth Model with Guludan Planting Technique in Angke Kapuk, Jakarta Coastal Area

Mangrove seedlings planted using the guludan technique are considered to produce optimal growth. Mangrove planting using guludan is an alternative for mangrove rehabilitation in former pond areas with deep water pools (more than 1 m). This study aimed to analyze the growth model of Rhizophora mucronata seedlings (growth in stem diameter and height, number of leaves, number of internodes, number of stilt roots) planted with guludan technique in Angke Kapuk, Jakarta Coastal Area. Measurements were made in the Angke Kapuk Mangrove Forest Area, Jakarta, in January 2019-April 2019. A total of 20 individuals from the 2018 planting year group were chosen as individual samples, were planted with Rhizhopora mucronata with a spacing of 0.5 m × 0.5 m. The data taken were the growth of stands, which include stem diameter, height, number of leaves, number of internodes, and number of stilt roots in the guludan. The results showed that the growth of stem diameter and height of R. mucronata seedlings for 12 weeks of observation formed a positive exponential equation. During the observation period (12 weeks) of the 20 R. mucronata seedlings seen, there were 380 leaves, 53 internodes, and four stilt roots growth.

Tolerance Mechanisms to Copper and Zinc Excess in Rhizophora mucronata Lam. Seedlings Involve Cell Wall Sequestration and Limited Translocation.

Rhizophora mucronata is a common mangrove growing in habitats subjected to heavy metal (HM) contamination. Understanding their physiological responses to copper (Cu) and zinc (Zn) excess and underlying tolerance mechanisms is crucial to assess impacts of metal pollution on mangrove community. Seedlings were treated with Cu or Zn (0, 50 or 100mg per plant) by means of a single addition. At day 3 and 7, Cu and Zn accumulation, photosynthetic efficiency, superoxide dismutase and peroxidase activity, non-protein thiols, reactive oxygen species and lipid peroxidation in roots and leaves were measured. R. mucronata restricted Cu and Zn translocation, thus accumulated HM mainly in roots while kept the leaves unaffected. However, high root HM did not induce oxidative stress nor anti-oxidative defense as HM were largely deposited in cell wall. We concluded that HM tolerance strategies of R. mucronata seedlings are exclusion and restriction of translocation to the vital photosynthetic tissue.

Structural and functional responses of xylem in <em>Rhizophora mucronata</em> Lam. seedlings under drought and hypersaline conditions

Water translocation in mangrove seedlings is often affected by water stress conditions such as drought, hyper-salinities and their frequent variations. This study was therefore aimed at studying the wood anatomical responses of xylem tissue and hydraulic conductivity of Rhizophora mucronata Lam., a common species in mangrove planting, under different levels of drought [25%, ~50% and ~100% of water holding capacity (WHC)] and soil salinity [high salinity (35 psu), moderate salinity (15 psu) and freshwater (0 psu)]. As wood anatomical responses, significantly higher vessel density, vessel grouping (P<0.001) along with narrow vessel elements (P<0.001) were observed in plants grown in the 25% and 50% WHCs and high salinity treatments. All these anatomical responses are more directed towards avoidance of vessel cavitation which is commonly found under water deficit conditions. The results showed that R. mucronata plants failed to maintain efficient transportation of water when the field capacity was 50% of WHC or lower and the level of salinity was 35 psu or greater, as evident by the reduction of water conductive areas, vessel areas and hydraulic conductivity (P<0.05). Overall, water use efficiency of R. mucronata seedlings under the imposed water stress conditions has remarkably reduced and it further indicated that such imposed stress conditions directly affect the survival of planted seedlings as depicted by the significantly low survival in 25% and 50% of WHCs and high salinity. Therefore, in-depth study on lagoon hydrology including inundation levels, water depth, salinity and the selection of correct tidal positioning is highly recommended as prerequisites in mangrove planting. Keywords. Hydraulic architecture, hydraulic conductivity, mangroves, restoration, water stress.

Evaluation of Rhizophora Mucronata Growth at first-year Mangrove Restoration at Abandoned Ponds, Langkat, North Sumatra

Degraded mangrove areas can be restored and rehabilitated. In Indonesia, one of the main recommended of mangrove species for restoration of degraded was Rhizophora mucronata. The purpose of the study was to evaluate R. mucronata growth at first-year mangrove restoration at abandoned shrimp ponds, Pulau Sembilan village, Langkat, North Sumatera, Indonesia. The recovery area divided into three zones based on the salinity concentration, landward, middle, and seaward zones. The evaluation parameters of mangrove reforestation consist of seedling diameter and height, leaves number, and seedling growth rate. Results showed that 3 of 4 evaluation parameters of R. mucronata growth belong to landward zone, namely seedlings diameter, the number of leaves, and percentage of growth. By contrast, height R. mucronata seedlings dominated in the middle area. The study also found that the proper zone for mangrove restoration with R. mucronata was in the landward with 96% growth rate and 30 part per thousand salinity concentration. The present study, therefore, suggested that the recommended species for the degraded area was the prerequisite for successful mangrove restoration.

Analysis on the Absolute Growth Rate of Rhizophora mucronata Seedling in Silvicultural Pond Canals by the Influence of Initial Condition and Changes of Environment Quality

&lt;p&gt;Mangrove seedling growth in silvofishery pond is limited to water quality dynamics while the water quality dynamically changes. This research aimed to study the changes of environmental factor condition in silvofishery pond and to analyze its impacts on the growth of mangrove seedling. Research experiment involved18 treatment plots with mangrove Rhizophora mucronata seedling. Observed parameters included temperature, turbidity, salinity, pH, DO, TSS, BO, N and P. Calculation was conducted for the deviation of each parameters. Mangrove growth parameters were including height and diameter growth while its data processing was absolute daily growth. Data analysis was conducted through regression. The result showed there were changes on environment parameters. Growth rate of R. mucronata showed variations on absolute daily height growth rate range of 0.215-3.333 mm/day (average 1.296 ±0.036 mm/day), while absolute daily diameter growth rate range was 2.15x10-3-0.196 mm/day (average 4.25x10-2 ± 3.59x10-2 mm/day). The analysis of regression showed several parameters effectedthe growth of mangrove seedlings including temperature, temperature change, turbidty, salinity change, pH, pH change, and DO on the growth of R. mucronata seedlings. This research concluded that environment parameters and its changes had significant effects on the growth of mangrove seedling. &lt;/p&gt;&lt;p&gt;&lt;strong&gt;How to Cite&lt;/strong&gt;&lt;/p&gt;&lt;p&gt;Hastuti, E., &amp;amp; Budihastuti, R. (2016). Analysis on the Absolute Growth Rate of Rhizophora mucronata Seedling in Silvicultural Pond Canals by the Influence of Initial Condition and Changes of Environment Quality. &lt;em&gt;Biosaintifika: Journal of Biology &amp;amp; Biology Education&lt;/em&gt;, 8(1), 56-63.&lt;/p&gt;

POTENTIAL OF MANGROVE SEEDLINGS FOR UTILIZATION IN THE MAINTENANCE OF ENVIRONMENTAL QUALITY WITHIN SILVOFISHERY PONDS

Silvofishery system has been applied to aquaculture activities and it has been developed in the coastal area of Semarang City, Indonesia. However, information on the initial development of silvofishery ponds concerning the functionality of mangrove seedlings on environmental quality of fish ponds had not been studied. This experiment aimed to determine the environmental conditions of silvofishery ponds and to analyze the effect of seedling stands of mangrove on environmental quality control. The presence of mangrove seedlings caused the decrease of temperature and the increase of salinity. ANOVA showed that mangrove species significantly affected water salinity, while canal width and mangrove species significantly affected turbidity and pH. Regression analysis showed that the height of Rhizophora mucronata had partially significant effect on Total Suspended Solids (TSS), Organic Matter (OM), as well as Nitrogen (N) and Phosphorus (P) concentrations. Diameter of R. mucronata affected temperature. The height and diameter of Avicennia marina affected Dissolved Oxygen (DO). Mixed populations of A. marina and R. mucronata had an effect on water turbidity, while population of only A. marina had a partial effect on water salinity. R. mucronata seedlings had dominant effect on the environmental quality. Mangrove seedlings can be used as environmental quality control within silvofishery ponds to maintain optimal conditions for fish growth. The application of silvofishery in early stage of mangrove seedlings should consider the more abundant plantation of R. mucronata compared to A. marina.Keywords: Canal width, environmental quality, seedling, silvofishery, species composition

Study on photosynthetic responses and chlorophyll fluorescence in Rhizophora mucronata seedlings under shade regimes

The photosynthetic performance of mangrove Rhizophora mucronata seedlings grown under seasonally full light (HL), 50 % shade (ML), and 80 % shade (LL) conditions was characterized by gas exchange, and chlorophyll fluorescence. The carboxylation efficiency significantly affected the seasonal change of the photosynthetic capacity. Temperature and light might have synergic effect on the carboxylation efficiency. The photosynthetic rate (PN) of R. mucronata seedlings under shade regimes, however, could not be attributed to variability in chlorophyll, C i , ΦPSII, ETR or qP values but more to differences in carboxylation efficiency, g max, and E max. HL and ML plants had higher PN, g s and E than the LL ones. Nevertheless, LL leaves exhibited low photoinhibition susceptibility. The high non-photochemical quenching in HL leaves may show that applied light intensity probably exceeded the photosynthetic capability. The findings indicate that ML treatments provided the best condition to obtain such carbon fixation capacity.

Dendrogram Zonasi Pertumbuhan Mangrove Berdasarkan Habitatnya di Kawasan Rehabilitasi Pantai Utara Jawa Tengah Bagian Barat

Dendrogram Zoning of Mangrove Growth Based on Its Habitat in the Rehabilitation Area on the North Coasts, West Region of Central JavaThe growth of rehabilitated mangrove, although planted at the same time, shows differences in terms of density and height growth. Such condition is visible in the North Shore of Brebes, Tegal and Pemalang Regency.The research result shows that mangrove growth planted in 2001 on the North Shore of Brebes, Tegal and Pemalang Regency is not apart from several factors, among others are its habitat physical-chemical factors. The result of regression correlation analysis shows that the habitat factors which play an important role in the vegetation density are salinity, temperature and plankton population. Meanwhile, the most dominant factor which determines the vegetation height growth is salinity and phosphor. The combination role based on its habitat shows that mangrove growth in Brebes Regency on proximal (1P) and medial (1M) zone and the one in Pemalang Regency on proximal zone (3P) has the shortest cluster, so that those research locations have similarity on vegetation growth and its habitat factors. Meanwhile, the proximal (2P) zone in Tegal Regency is similar with the medial (2M) zone. Mangrove growth on distal zone in Tegal Regency has less good growth parameter and habitat factors compared to that of in Brebes and Pemalang for containing more sand.From the research result, it can be concluded that the existence of habitat factors salinity, plankton population and phosphor have to be taken into consideration if a mangrove area will be rehabilitated/planted especially using Rhizophora mucronata seedlings. In order to reach the maximum achievement, one thing which has to be taken into consideration is the habitat clustering of the planted area, especially in Brebes, Tegal and Pemalang Regency area.

Present status of mangroves in three different water bodies associated sites in Thirukkovil and Pottuvil, Ampara district

Thirukkovil and Pottuvil villages in Ampara district are well known for Ecotourism. Village ecotourism is based on the beauty of the coastal belt and its surrounds which is decorated by flora and fauna within its geographical sites. A predominant flora of the coastal villages, along the water bodies are mangroves and this was either fully or partially devastated by tsunami tidal waves in 2004. Studing the present status of mangroves is important for the ecotourism since it enables the present plant forms and by replanting the appropriate species. The aim of the study was to evaluated the present status of mangroves, in the three selected water bodies associate sites namely Maranakandy River in Thirukkovil, Kudakali Lagoon &amp; Dhua Lagoon in Pottuvil, Ampara district, which was carried out in July 2006. An impact of tidal waves on mangroves and its associates was not clearly evident in Maranakandy River, where an impact was clearly seen in Kudakali lagoon, but least was noted in Dhua lagoon, at the time of study. This impact difference possibly by the distances of sea point’s from the sites and the types of mangrove vegetation the sites had at that time. Maranakandy River was under continuous exploitation by local communities compared to Kudakali lagoon and Dhua lagoon, which located next to each other, but at a distance and an undisturbed state. Both true and associated mangroves species were naturally segregated in all three sites. Predominant species was Rhizophora sp, except in Dhua lagoon. In Dhua lagoon, along the sites, but opposite to the sea, root stumps and prop roots were left out as evident destructive parts of Rhizophora sp. by tidal waves impact and no species were seen in the premises. Rhizophora sp. was grown adjacent and along the sites in Maranakandy River and Kudakali lagoon, where Excoecaria agallocha and Bruguiera gymnorhiza were at its immediate right backyard, respectively. R. mucronata showed a stunted growth in Maranakandy River, where as R. apiculata recorded in Kudakali lagoon was overgrown to a height of 6 m. As such, a morphological habit of R. apiculata possibly served as a colliding object for the impact of tidal waves in Kudakali lagoon and thus impact of tidal waves was greater on R. apiculata, mainly at the entry point of sea water. Tall grown B. gymnorhiza was only recorded in Kudakali lagoon and impact of tidal waves were negligible, since R. apiculata was in the frontier line and sacrificed first while safe guarded the B. gymnorhiza. Natural regenerations by numerous B. gymnorhiza seedlings were seen and being occupied in the devastated sites of R. apiculata in Kudakali lagoon. Replantation of R. mucronata seedlings were noted in Maranakandy River, except in Dhua lagoon. Thus, on site basis, a planned replantation of mangroves is necessary to uplift the socio-economic life of three sites in the district, perhaps ecotourism.

The effects of environmental variables on mortality and growth of mangroves at Mngazana Estuary, Eastern Cape, South Africa

This study investigated the effects of environmental variables on mortality and growth of three mangrove species at Mngazana Estuary—Eastern Cape, South Africa, to determine the sustainability of harvesting at this estuary. Environmental variables changed with the sediment composition in the estuary, whereby moisture content and organic matter were positively correlated to silt content. A decrease in sediment pH increased the mortality of Avicennia marina seedlings (r = −0.71, p < 0.05) and decreased the growth of Rhizophoramucronata and Bruguiera gymnorrhiza seedlings (r = −0.8, r = 0.52, p < 0.05, respectively). The mortality of B. gymnorrhiza showed a positive correlation with sediment moisture content indicating that this species prefers drier conditions. The vertical growth rate of A. marina individuals increased from seedlings (0.31 ± 0.07 cm month−1) to adults (1.2 ± 0.2 cm month−1) whereas the growth of B. gymnorrhiza was not significantly different for trees of 150 cm height and taller (0.65 ± 0.1 cm month−1). The vertical growth of R. mucronata peaked at 0.72 ± 0.1 cm month−1 at a height of 151–250 cm. If the differences in vertical growth rate for each size class were taken into account, it will take approximately 13 years for R. mucronata seedlings, the preferred species for harvesting, to grow to a height of 390 cm. This is the preferred height at which trees are selected for harvesting at this estuary. Mangroves are harvested for building material (poles) and firewood. This is 2.6 times slower than those individuals growing in Gazi Bay situated in southern Kenya, along the east coast of Africa. Data from this study indicate that it is not sustainable to harvest mangroves from the forest due to the slow (vertical and horizontal) growth rate of individuals and the length of time required for new individuals to grow to the preferred height for harvesting.

The response of the red mangrove Rhizophora mucronata Lam. to salinity and inundation in South Africa

Salinity and water level fluctuations are important factors that influence mangrove species distribution, zonation patterns and succession. Increases in salinity and prolonged inundation are predicted along the south eastern African coast associated with sea level rise due to climate change. This study investigated the response of red mangrove seedlings ( Rhizophora mucronata Lam.) to these factors in controlled laboratory experiments. Seedlings were exposed to five salinity treatments (0, 8, 18, 35 and 45 PSU) and a semi-diurnal tidal cycle in an experimental tank set-up. In a separate experiment the effects of different inundation treatments: no inundation, 3, 6, 9 h tidal cycles and continuous inundation (24 h) were investigated. Both morphological and physiological responses of R. mucronata seedlings were measured. There was a decrease in growth (plant height, biomass and leaf production) with increasing salinity. Seedlings in the seawater, hypersaline and no inundation treatments showed symptoms of stress such as increased leaf necrosis (‘burn marks’). The highest seedling growth occurred in the low salinity (8 PSU) treatment, but the highest photosynthetic performance and stomatal conductance occurred in the freshwater treatment (0 PSU). The typical response of stem elongation with increasing inundation was observed in the 24 h inundation treatment. Seedlings in the no inundation treatment had significantly lower seedling height compared to the other treatments.

Effects of vegetation and sewage load on mangrove crab condition using experimental mesocosms

Constructed wetlands, especially mangroves, have been studied for their usefulness in sewage treatment but the effects of mangrove vegetation and a sewage load on mangrove macrofauna have been given little attention. Ocypodid crabs are important components of mangrove forests and constitute good bioindicators of the functioning of the ecosystem as a whole. In constructed mangrove mesocosms, three vegetation treatments (bare substratum, and Avicennia marina and Rhizophora mucronata seedlings) were subjected to 0, 20, 60 and 100% sewage loads from a nearby hotel. The physiological condition of introduced Uca annulipes and Uca inversa was evaluated in terms of their RNA/DNA ratio after one, five and twelve months, and used as an indicator of ecological function in the system. Crab condition in 0% sewage load was similar to that of wild crabs throughout, suggesting no significant effects of the mesocosms on their RNA/DNA ratio. Overall, both species coped well with the administered sewage loads, suggesting good ecological function in the system. Both species manifested similar patterns in RNA/DNA ratio, being more affected by seasonal fluctuations than by sewage load and vegetation presence and type. Higher RNA/DNA ratios were recorded in the long compared to the short rainy season. Sewage enhanced crab condition in the bare substratum and R. mucronata treatments, especially after one year, probably as a result of enhanced food availability. Uca inversa may be more sensitive to sewage pollution than U. annulipes. In A. marina, no difference in crab condition was observed between sewage loads, and this mangrove yielded the best reduction in sewage impacts. Our results support the usefulness of constructed mangrove areas in sewage treatment, especially if planted with A. marina and inhabited by physiologically healthy ocypodid crabs to enhance the system's performance.

Spraying seawater as an effective method to control Aulacaspis marina Takagi and Williams (Homoptera : Diaspididae), a mangrove infesting scale insect in Indonesia.

The scale insect, Aulacaspic marina Takagi and Williams, has killed a large number of mangroves, Rhizophora mucronata Lamk., planted in abandoned shrimp ponds on Bali Island, Indonesia. In this study, we developed a control method for A. marina using seawater. An examination of the relationship between tree height and leaf damage in an R. mucronata plantation indicated that A. marina did not damage R. mucronata when the saplings were lower than the highest sea level of the spring tide, resulting in the saplings being periodically submerged in seawater by changes in tidal level. To examine how seawater submergence prevents this damage, crawlers of A. marina were artificially transferred to R. mucronata seedlings on which seawater or fresh water were sprayed daily. The crawlers settled on more than 90% of the leaves in fresh-water-sprayed and unsprayed seedlings but only on 37% of the leaves in seawater-sprayed seedlings, indicating that seawater helped prevent crawler settlement. To develop a control method using this seawater effect, seawater was sprayed on damaged saplings in an R. mucronata plantation at weekly intervals using two types of sprayers. In these saplings, leaf damage was lower than that of control saplings after spraying for five or nine weeks for each type of sprayer, respectively. This indicates that periodic spraying of seawater is an effective control measure against A. marina.

Life history of Aulacaspis marina Takagi and Williams(Hom., Coccoidea), a new pest of mangrove plantations in Indonesia, and its damage to mangrove seedlings

Scale insects of a newly described species, Aulacaspis marina Takagi and Williams, have killed a large number of mangrove (Rhizophora mucronata Lamk.) saplings planted in abandoned shrimp ponds on Bali island, Indonesia. The mean fecundity of A. marina was 141 eggs. The generation time of this species was between 34 and 42 days, based on four generations, suggesting that the species has nine to 10 generations a year on Bali island where the temperatures are seasonally constant. When crawlers of A. marina were transferred to potted seedlings of R. mucronata, they settled on all leaves of the seedlings. Newly expanded leaves were not infested by the first generation crawlers but were attacked by the following generations. The insect attack induced browning of the leaves and finally caused leaf fall; the leaves fell 25–159 days after the crawler transfer. Consequently, the seedlings died on average 128 (range 82–159) days after infestation. This suggests that once a large number of crawlers attack R. mucronata seedlings, A. marina can kill them within several months. When crawlers were transferred to potted seedlings of three mangrove species (R. mucronata, Rhizophora apiculata Bl. and Bruguiera gymnorrhiza L.), which were the main species planted at the study site, the numbers that developed into adult females did not differ significantly among these species. This suggests that these mangrove species are almost equally susceptible to A. marina.

The physiological significance of the leaf nodules of psychotria

In 6-month growth experiments it was found that leaf-nodulatedPsychotria mucronata seedlings grown in N-poor soil showed a restricted growth and developed severe nitrogen-deficiency symptoms in the leaves. Plants in the same soil supplied with NO3-N showed healthy growth and dark green leaves. Detached Psychotria leaves bearing leaf nodules exposed to an atmosphere containing N15-labelled nitrogen gas or acetylene gas gave no evidence of nitrogen fixation, either in the light or in the dark or in both in succession. Therefore nitrogen fixation is probably not associated with the leaf nodules.