Terms Of Dry Weight Research Articles

Influence of salt stress on growth, lipid peroxidation and antioxidative enzyme activity in borage (Borago officinalis L.)

The effects of increasing salt concentrations on the growth, electrolyte leakage, lipid peroxidation, and major antioxidant enzyme activities (superoxide dismutase, catalase, ascorbate peroxidase and glutathione reductase) of borage plants were investigated. Plants were grown in half strength of Hoagland nutrient solution added with 0, 25, 50, and 75 mM of NaCl. Most measured parameters were affected by salinity. Increasing salt levels caused a significant reduction in leaf area, stem length, stem diameter, flower number, and dry masses of different organs. Growth of borage plants, in terms of dry weight, was affected. As a consequence of salinity stress, lipid peroxidation and membrane permeability was increased. Antioxidant activity showed an increase in the activity of superoxide dismutase, a non-induced activity of catalase and ascorbate peroxidase, and a slight increase in glutathione reductase activity. The results indicate that borage plants appear to be sensitive to salt stress, since enzymes related to antioxidant enzymatic defense system in treated leaves should be highly active.

Fleshy fruit characteristics in a temperate deciduous forest of Japan: how unique are they?

This study investigated the fleshy fruit characteristics of 28 woody species in a Japanese temperate forest where large sedentary seed-dispersing mammals are present. We tested whether the findings in previous studies in temperate forests of Europe and North America are universal or not. Results have suggested that fruits of all species were eaten both by birds and mammals except for four species with larger fruits, which were eaten only by mammals. A gradient was found from a syndrome characterized by small, oily, and large-seeded fruits to a syndrome characterized by large, succulent, non-oily, and small-seeded fruits. The sizes and colors of the fruits were not conspicuously different from previous findings in Europe and North America. On the other hand, nitrogen and lipids in the fleshy part did not show seasonally increasing trends, or even seasonally decreasing trends in terms of dry weight. This result, suggesting the absence of community-level adaptation of fruit traits to migratory bird dispersers, contrasted with findings in Europe and North America. Large sedentary arboreal or tree-climbing mammals may have a greater effect on the evolution of fruit-disperser relations than opportunistic migratory birds.

In vitro Callus Induction and Plant Regeneration From Withania coagulans: A Valuable Medicinal Plant

Leaf and internode explants of Withania coagulans Dunal were used to evaluate the effect of growth regulators on the in vitro callus induction and plant regeneration. Two independent experiments were performed to establish callus and plant regeneration. In the first experiment, leaf segments were cultured on MS basal medium fortified with 2, 4-dichlorophenoxyacetic acid (2, 4-D, 2-4 mg L(-1)) with combination of 6-benzyladenine (BA, 0.5-1 mg L(-1)) or kinetin (Kin, 0.5-1 mg L(-1)). Callus initiation was observed best in all media after 14-16 days (100%). Highest callus growth in terms of dry weight (76 +/- 5.34 mg) was observed in MS medium fortified with 2 mg L(-1) 2, 4-D and 0.5 mg L(-1) Kin. In the second experiment, callusing also obtained from internode segments cultured on MS medium with the presence of 2, 4-D (2-4 mg L(-1)) in association with BA (0.25-0.5 mg L(-1)). Best callusing rates (42%) and dry weight (86 +/- 3.68 mg) occurred in the presence of 4 mg L(-1) 2, 4-D with combination of 0.25 mg L(-1) BA. Shoot induction was obtained just from callus induced from internode explants on MS medium containing BA (2 mg L(-1)) with IBA (0.5 mg L(-1)), but the yield of shoot regeneration was unsatisfactory (18-33%). Regenerated shoots were rooted best (100%) on half strength MS medium containing IBA (2 mg L(-1)) and produced 23 roots with an average root length of 6.5 +/- 0.41 cm. Rooted plantlets transferred to soil and sand mixture (2:1) showed 75% survival when transferred to outdoor. The procedure reported here in vitro culture of W. coagulans for first time.

Effects of Desiccation and Sediment Type on Early Regeneration of Plant Fragments of Three Species of Aquatic Macrophytes

AbstractWe tested the effects of desiccation and type of sediment (clay or sand) on the regeneration of fragments of the apical shoots of three species of Hydrocharitaceae: Egeria najas, E. densa and Hydrilla verticillata. The shoots were left to dry on clay or sand from zero to four days, and were then returned to aquaria containing water. To approximate natural conditions, the aquaria containing clay had higher turbidity and nutrient (P and N) concentrations than did the aquaria with sand. All species dried faster on sand substrate, which led to lower regeneration (in terms of dry weight, length, sprout and root formation) in this treatment. H. verticillata fragments elongated faster than the other species, but E. najas was the most successful species (in terms of increase in dry weight) in the sand treatment. Our results indicate that the exotic H. verticillata has a competitive advantage, at least in its early stages of regeneration, over the other two, native species, especially in more eutrophic and turbid habitats; whereas E. najas fragments have a competitive advantage in less‐turbid, oligotrophic and sand‐dominated sites. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Winter distribution of euphausiids (Euphausiacea) in the Barents Sea (2000–2005)

Abstract The purpose of the study is to analyze the state of the Barents Sea euphausiids populations in the warm period (2000–2005) based on the study of their structure dynamics and distribution under the influence of abiotic and biotic factors. For estimation of their aggregations in the bottom layer, the traditional method was used with the help of the modified egg net (0.2 m 2 opening area, 564 μm mesh size). The net is used for collecting euphausiids in the autumn–winter period when their activity is reduced, which results in high-catch efficiency. The findings confirmed the major formation patterns of the euphausiids species composition associated with climate change in the Arctic basin. As before, in the warm years, one can see a clear-cut differentiation of space distribution of the dominant euphausiids Thysanoessa genus with localization of the more thermophilic Thysanoessa inermis in the north-west Barents Sea and Thysanoessa raschii in the east. The major euphausiids aggregations are formed of these species. In 2004, the first data of euphausiids distribution in the northern Barents Sea (77–79°N) were obtained, and demonstrated extremely high concentrations of T. inermis in this area, with the biomass as high as 1.7–2.4 g m −2 in terms of dry weight. These data have improved our knowledge of the distribution and euphausiids abundance during periods of elevated sea-water temperatures in the Barents Sea. The oceanic Atlantic species were found to increase in abundance due to elevated advection to the Barents Sea during the study period. Thus, after nearly a 30-year-long absence of the moderate subtropical Nematoscelis megalops in the Barents Sea, they were found again in 2003–2005. However in comparison with 1960, the north-east border of its distribution considerably shifted to 73°50′N 50°22′E. The portion of Meganyctiphanes norvegica also varied considerably—from 10% to 20% of the total euphausiids population in the warm 1950s–1960s almost to complete disappearing in 1970–1990s. The peak of this species’ occurrence (18–26%) took place in the beginning of warm period (1999–2000) after a succession of cold years. The subsequent reduction of the relative abundance of M. norvegica to 7% might have been mostly caused by fish predation during a period of low population densities of capelin. This high predation pressure may therefore have been mediated both by other pelagic fishes (i.e. herring, blue whiting, polar cod) but also by demersal fishes such as cod and haddock. Similar sharp fluctuations in the capelin stock (the major consumer of euphausiids) created marked perturbations in the food web in the Barents Sea in the middle 1980s and the early 1990s.

Conversion of crude chitosan to an anti-fungal protease by Bacillus cereus

Bacillus cereus AU004, isolated from soil samples, secreted a complex of hydrolytic enzymes into the culture broth when it was grown aerobically in a medium containing crude chitosan flakes. The presence of the AU004 culture supernatant substantially influenced the growths of the plant-pathogenic fungi Fusarium oxysporum, F. solani and Pythium ultimum in terms of dry weight. AU004 excreted a protease when cultivated in a medium that contained 4% (w/v) chitosan as the major nutritional source. The protease was purified by sequential chromatography and characterized as a novel extracellularly neutral protease. The protease had an Mr of 28.8 kDa. The optimal pH and temperature for protease activity were 7 and 50°C, respectively. Antifungal activity of the protease was observed using an assay based on the inhibition of spore germination and hyphal extension of the fungal Pythium ultimum. This investigation is the first report of the production of an anti-fungal protease from Bacillus spp.

Relationship between gibberellic acid and water amount in the cotton seed

The role of endogenous GA3 and its application to seed development in two cotton genotypes Hybrid-6 (H-6) (big seeds) and Gujarat cotton 13 (G. Cot) (small seeds) was studied. Kernel and seed coat were subjected to growth analysis in terms of dry weight, water amount, and rates of dry matter accumulation and water uptake. H-6 kernel had manifold higher dry weight and water amount than G. Cot. Seed coat of both genotypes had similar dry weight at maturity, but the maximum rates of dry matter accumulation and water uptake were distinctly higher in H-6. According to growth analysis, development of seed kernel and coat was subdivided into four phases, i.e., cell division, cell elongation, dry matter accumulation and maturation. Endogenous GA3 level was estimated in kernel and seed coat by indirect ELISA using antibodies raised against GA3. GA3 amount per seed components was higher in the seed kernel of H-6 than of G. Cot, except 33 and 36 days after anthesis in kernel. H-6 seed coat had the higher amount of GA3 during cell division phase than that of G. Cot. Close correlation between in vivo GA3 level and water amount was recorded in both seed components. With GA3 or GA3 + NAA treatments in ovule culture, higher promotion in dry weight, water amount and seed size was noted in G. Cot than in H-6 suggesting that G. Cot is more deficient in endogenous GA3. The greatest stimulation of parameters studied was obtained in ovule culture with GA3 + NAA. When GA3 or GA3 + NAA was applied, initial significant difference in water amount and seed size was nullified. Data presented in this study indicated that GA3 regulates cell expansion through the water uptake by cotton seed.

Harvesting and Processing Zooplankton for Use as Supplemental Channel Catfish Fry Feed

AbstractWe present the methods that we used to capture and dry large zooplankton from ponds to feed to channel catfish Ictalurus punctatus fry. Using a submersible pump and canister filter, we were able to capture about 1.0 kg (wet weight; 200 g in terms of dry weight) of zooplankton from well‐fertilized ponds over 24‐h trapping periods. This was a practical method for obtaining the large zooplankton that catfish fry prefer. Fish culturists may be able to use this method to harvest zooplankton throughout the year and store dried zooplankton for the hatchery season. The drying process may also be useful for processing and storing small zooplankton for the culture of other species of fish. The cost was about US$200 for the submersible pump, $200 for the canister and filter, and $40 for the food dehydrator.

Introduction of a novel pathway for IAA biosynthesis to rhizobia alters vetch root nodule development

We introduced into Rhizobium leguminosarum bv. viciae LPR1105 a new pathway for the biosynthesis of the auxin, indole-3-acetic acid (IAA), under the control of a stationary phase-activated promoter active both in free-living bacteria and bacteroids. The newly introduced genes are the iaaM gene from Pseudomonas savastanoi and the tms2 gene from Agrobacterium tumefaciens. Free-living bacteria harbouring the promoter-iaaMtms2 construct release into the growth medium 14-fold more IAA than the wild-type parental strain. This IAA overproducing R. l. viciae, the RD20 strain, elicits the development of vetch root nodules containing up to 60-fold more IAA than nodules infected by the wild-type strain LPR1105. Vetch root nodules derived from RD20 are fewer in number per plant, heavier in terms of dry weight and show an enlarged and more active meristem. A significant increase in acetylene reduction activity was measured in nodules elicited in vetch by RD20.

Nitrogen stress induction on Levisticum officinale hairy roots grown in darkness and under photoperiod conditions: effect on growth and volatile components

Six-year-old Levisticum officinale (lovage) hairy root cultures were used to study the effect of eight different NH(4) (+):NO(3) (-) ratios on their growth and volatile components. All cultures were kept at 24 degrees C on orbital shakers at 80 rpm, in darkness or in a 16 h light/8 h dark photoperiod. Growth was evaluated by dry and fresh weight determination. The volatiles were isolated by distillation-extraction and analysed by GC and GC-MS. Greater growth was attained in darkness with 10:90 (control, SH medium), 50:50 and 25:75 NH(4) (+):NO(3) (-) ratios, and also with SH control medium under the photoperiod condition, with a 10, 14, 12.5 and 12.5 fold increase of biomass in terms of dry weight, respectively, at the end of 42 days of growth. UPGMA cluster analysis of the mixtures of volatiles isolated from the hairy roots grown with different NH(4) (+):NO(3) (-) ratios confirmed their chemical variability. Although no particular grouping was detected in relation to the NH(4) (+):NO(3) (-) ratios or light conditions studied, most of the mixtures of volatiles isolated from the hairy roots were either dominated by n-octanal, (Z)-falcarinol or both components in about the same relative amounts.

Influence of P Fertilization on Biological Nitrogen Fixation in Herbaceous Legumes Grown in Acid Savannah Soils from the Tabasco State, Mexico

gThe use of leguminous plants in the agricultural systems of the humid tropics is an alternative means for providing N to soils considered unfertile and marginal. The objective of this study was to assess the biological nitrogen fixation (BNF) in the symbiosis Rhizobia-herbaceous legumes (Mucuna deeringiana, Canavalia ensiformis, Vigna umbellata, Cajanus cajan, Dolichos lablab, Arachis pintoi and Crotala-riajuncea) grown in acid soil amended with P fertilizer by the 15N-isoto-pic dilution technique (“A”-value) using maize, Brachiaria spp. and no nodulating common bean as reference crops. Results indicate a positive effect of P-fertilizer on parameters associated with BNF and biomass accumulation. The legumes Cajanus cajan and Canavalia ensiformis showed good performance in terms of dry weight of nodules (C. cajan = 758 and C ensiformis = 500 mg nodules plant−1 with 49 and 56 nodules plant−1, respectively) at flowering stage, and BNF (C. cajan = 170 and C ensiformis = 366 kg N ha−1 cycle−1) when 80 kg P205 ha−1 was applied to soil. Maize ‘VS-486’ and ‘VS-536’ and non-nodulating common bean ‘DOR 364’ were adequate reference crops to estimate the N derived from the atmosphere by the legume species. The results indicate that C ensiformis and C cajan have a good potential to be used as green manure in the Huimanguillo savannah, Tabasco State, Mexico.

Abstracts of Nippon Dojo-Hiryogaku Zasshi (Japanese Journal of Soil Science and Plant Nutrition)

Abstracts of Nippon Dojo-Hiryogaku Zasshi (Japanese Journal of Soil Science and Plant Nutrition)

Responses of Rice Cultivars with Different Nitrogen Use Efficiency to Partial Nitrate Nutrition

There is increased evidence that partial nitrate (NO3-) nutrition (PNN) improves growth of rice (Oryza sativa), although the crop prefers ammonium (NH4+) to NO3- nutrition. It is not known whether the response to NO3- supply is related to nitrogen (N) use efficiency (NUE) in rice cultivars. Methods Solution culture experiments were carried out to study the response of two rice cultivars, Nanguang (High-NUE) and Elio (Low-NUE), to partial NO3- supply in terms of dry weight, N accumulation, grain yield, NH4+ uptake and ammonium transporter expression [real-time polymerase chain reaction (PCR)]. A ratio of 75/25 NH4+ -N/NO3- -N increased dry weight, N accumulation and grain yield of 'Nanguang' by 30, 36 and 21 %, respectively, but no effect was found in 'Elio' when compared with those of 100/0 NH4+ -N/NO3- -N. Uptake experiments with 15N-NH4+ showed that NO3- increased NH4+ uptake efficiency in 'Nanguang' by increasing Vmax (14 %), but there was no effect on Km. This indicated that partial replacement of NH4+ by NO3- could increase the number of the ammonium transporters but did not affect the affinity of the transporters for NH4+. Real-time PCR showed that expression of OsAMT1s in 'Nanguang' was improved by PNN, while that in 'Elio' did not change, which is in accordance with the differing responses of these two cultivars to PNN. Conclusions Increased NUE by PNN can be attributed to improved N uptake. The rice cultivar with a higher NUE has a more positive response to PNN than that with a low NUE, suggesting that there might be a relationship between PNN and NUE.

Submerged culture conditions for mycelial yield and polysaccharides production by Lyophyllum decastes

The effects of various carbon and nitrogen sources, their concentrations, initial pH and fermentation duration on the production of mycelia in terms of dry weight, exo-polysaccharide (EPS) and inner polysaccharide (IPS) by Lyophyllum decastes, a culinary-medicinal mushroom, were investigated in shake-flask cultures. Lactose, glucose and fructose were the top three best carbon sources for mycelial growth with corresponding yields of 6.73 g/l, 6.36 g/l and 6.10 g/l, respectively. Glucose was the best for production of EPS and IPS with 1.65 g/l and 317 mg/g dry mycelia, respectively. Maltose also performed well for EPS production. Yeast extract was the best nitrogen source for the production of mycelia (7.03 g/l) and IPS (325 mg/g dry mycelia), whereas EPS was improved further by increasing the yeast extract concentration (2.46 g/l at 2%). Similarly, initial pH 7 and 8 were best for polysaccharides production (EPS 1.73 g/l and IPS 320 mg/g) and mycelial growth (7.10 g/l), respectively. Maximum mycelial growth peaked at 15 days of cultivation whereas polysaccharides peaked at 10 days, and then tapered off. A concentration of glucose 3% and yeast extract 1% (mycelial yield and IPS) were found to be a suitable condition for submerged culture.

Benefits of clonal integration between interconnected ramets of Vallisneria spiralis in heterogeneous light environments

Interconnected ramets of the submersed macrophyte Vallisneria spiralis were subjected to two homogeneous treatments (shading or not shading whole plants) and two heterogeneous treatments (only shading basal or apical ramets of plants). The benefits and costs of clonal integration between connected ramets grown in heterogeneous treatments were examined. Results showed that shading apical ramets induced significant benefits to the performance of whole plant in terms of dry weight per plant ( P < 0.01) and number of ramets per plant ( P < 0.05). Especially for the unshaded basal ramets, their dry weight, number of ramets, number of branches and total stolon length were 89%, 30%, 29% and 58% higher than the corresponding ramets in homogeneous treatment, respectively. Compared to their controls in homogeneous treatments, unshaded basal ramets produced more leaf mass (0.15 g versus 0.11 g) whereas shaded apical ramets produced more root mass (0.012 g versus 0.008 g). However, there was a different pattern of integration when basal ramets were shaded. Shading basal ramets led to a significant decrease in stolon growth, but the individual performance of shaded ramets improved. Cost-benefit analyses revealed that dry weight per ramet of basal shaded ramets was 31% greater than that of basal shaded ramets in the homogeneous treatment. We can conclude that V. spiralis can benefit from clonal integration in heterogeneous light environments, but that the scale of these benefits is related to the quality of light environments where the clone become established.

Carbon and nitrogen balance of leaf-eating sesarmid crabs ( Neoepisesarma versicolor) offered different food sources

Carbon and nitrogen budgets for the leaf-eating crab, Neoepisesarma versicolor, were established for individuals living on pure leaf diets. Crabs were fed fresh (green), senescent (yellow) and partly degraded (brown) leaves of the mangrove tree Rhizophora apiculata. Ingestion, egestion and metabolic loss of carbon and nitrogen were determined from laboratory experiments. In addition, bacterial abundance in various compartments of the crabs' digestive tract was enumerated after dissection of live individuals. Ingestion and egestion rates (in terms of dry weight) were highest, while the assimilation efficiency was poorest for crabs fed on brown leaves. The low assimilation efficiency was more than counteracted by the high ingestion rate providing more carbon for growth than for crabs fed green and yellow leaves. In any case, the results show that all types of leaves can provide adequate carbon while nitrogen was insufficient to support both maintenance (yellow leaves) and growth (green, yellow and brown leaves). Leaf-eating crabs must therefore obtain supplementary nitrogen by other means in order to meet their nitrogen requirement. Three hypotheses were evaluated: (1) crabs supplement their diet with bacteria and benthic microalgae by ingesting own faeces and/or selective grazing at the sediment surface; (2) assimilation of symbiotic nitrogen-fixing bacteria in the crabs' own intestinal system; and (3) nitrogen storage following occasional feeding on animal tissues (e.g. meiofauna and carcasses). It appears that hypothesis 1 is of limited importance for N. versicolor since faeces and sediment can only supply a minor fraction of the missing nitrogen due to physical constraints on the amount of material the crabs can consume. Hypothesis 2 can be ruled out because tests showed no nitrogen fixation activity in the intestinal system of N. versicolor. It is therefore likely that leaf-eating crabs provide most of their nitrogen requirement from intracellular deposits following occasionally ingestion of animal tissue (hypothesis 3).

A new marine medium: Use of different fish peptones and comparative study of the growth of selected species of marine bacteria

Various readily obtainable ‘marine’ media from fishery residues were evaluated against a common commercial medium for their effectiveness for promoting growth of different bacteria. The microorganisms investigated (genera Pseudomonas, Vibrio, Roseobacter) are of interest to aquaculture either for their pathogenic or probiotic character. Comparisons between the media were centered on the most important kinetic parameters of the corresponding cultures, i.e., maximum biomass and maximum specific growth rate, calculated by applying two widely accepted mathematical models (logistic and Gompertz equations) to data measured both in terms of dry weights and cell numbers. The parametric estimations allowed a classification of the results that demostrated the effectiveness of all the media derived from fishery residues to meeting the proposed objectives. Growths were generally superior (up to 10 times in terms of cell numbers) to those from the common commercial medium, with the best results obtained from tuna viscera.

Feasibility study of a tissue-specific approach to barley proteome analysis: aleurone layer, endosperm, embryo and single seeds

Proteome analysis in the pI 4–7 range of aqueous extracts from whole barley seeds results in complex 2D-gel spot patterns that represent proteins from all seed tissues. Proteins were extracted from dissected aleurone layer, embryo and endosperm for separate analysis of these components and comparison with single seed extracts. The analysis showed that while the starchy endosperm comprises approximately 85% of the mature seed dry weight, it contributes less than 50% of the soluble protein to seed extracts. Although the aleurone layer and embryo are minor components of the seed in terms of dry weight, their proteins contribute significantly to the 2D-gel pattern. Distinct but overlapping patterns were observed for the dissected tissues. While whole seed gels contained about 850 spots, endosperm, aleurone layer and embryo gels had about 575, 850 and 1000 spots, respectively, representing a total increase of at least 15%. Protein patterns were also reduced in complexity and this enrichment of subsets of proteins facilitated identification by mass spectrometry of proteins of interest in mature seed tissues and developing endosperm. These techniques can therefore be used with advantage to describe the proteomes of dissected seed tissues.

Some quantitative aspects of seagrass ecology in a coastal lagoon of Mauritius

Seagrass distribution was recorded by snorkel dives on a grid of stations in the waterfront of Club Mediterranee at Mon Choisy–Trou Aux Biches lagoon (NW Mauritius) and subsequently mapped using SURFER 6 computer software. Above-ground (AG) and below-ground (BG) standing biomass in terms of dry weight (DW) and ash-free dry weight (AFDW) as well as shoot density and shoot length were monitored monthly from June1997 to May1998 in a mixed stand of Haloduleuninervis and Syringodiumisoetifolium (dominant) at a shallow, nearshore station in the lagoon. Measurements of physical and chemical parameters [water temperature, current speed, salinity, pH, dissolved oxygen (DO), nitrate and phosphate concentrations] were made simultaneously, as well as at a reference station (ORE) outside the coral reef. The bottom sediment was analysed for grain size and type composition. Variation patterns were examined and statistical correlations drawn to relate plant performance to the environmental variables measured. The SURFER 6 programme generated a satisfactory contour map of seagrass distribution in the lagoon with a cover range of 0–60%. The densest patches occurred adjacent to the shoreline experiencing weaker water currents (3–13 cm s–1) rather than near the reef (5–35 cm s–1), where seagrasses were absent. Sand (0.063–2 mm grain size) constituted 97.2% and 77.6% of the nearshore and near-reef sediment, respectively. The dominant grain types were derived from corals (about 80%) and mollusc shells (about 14%). The recorded range of total standing biomass for H. uninervis was 243.1–468.2 g DW m–2 (326.9±71.7 g) or 71.7–141.2 g AFDW m–2 (96.8±20.1 g) and for S. isoetifolium it was 271.7–758 g DW m–2 (460.4±167.1 g) or 119–220.5 g AFDW m–2 (155.1±26.5 g), with a maximum biomass increase during September–December in both species. AG:BG biomass ratios were generally <1 and approximated 1 during the warmest months of December–February only. Mean shoot density (1,077–4,364 shoots m–2 in the overall range of 998–4,428 shoots m–2) and mean shoot length (10.9–20.8 cm in the overall range of 7–31 cm) in S. isoetifolium were higher than in H. uninervis (1,732–4,137 shoots m–2 in the overall range of 1,522–4,327 shoots m–2 and 7.9–13.7 cm in the overall range of 6–20 cm, respectively). Temperature showed strong positive correlations with total AFDW biomass of both species (r=0.755, P<0.01 for H. uninervis; r=0.679, P<0.02 for S. isoetifolium) and with DO (r=0.925, P<0.01). High DO levels (10.7–11.2 mg l–1) coincided with optimum standing biomass at 27.2°C. Correlations were also strong with shoot density (r=0.881, P<0.01 for H. uninervis; r=0.952, P<0.01 for S. isoetifolium) and shoot length (r=0.752, P<0.01 for H. uninervis; r=0.797, P<0.01 for S. isoetifolium). Under optimal environmental conditions, nutrient inputs from surface run-off or underground freshwater seepage in the lagoon due to heavy rainfall may boost up seagrass biomass, as suggested by positive significant correlations between phosphate levels and AG AFDW biomass (r=0.63, P<0.05 for H. uninervis; r=0.65, P<0.05 for S. isoetifolium) and shoot density (r=0.6, P<0.05 for H. uninervis; r=0.687, P<0.02 for S. isoetifolium). The results generated in this study suggest local seagrass standing biomass is comparable to that reported in monospecific stands from elsewhere. Anthropogenic activities increasingly draw down the resilience of the seagrass beds around Mauritius, and preventative measures are indispensable to achieve coastal ecological stability.

Characterization of capacitive sensors for measurements of the moisture in irrigated soils

The irrigation is a technique developed to supply the hydric needs of the plants. The use of the water should be optimized so that the culture just has enough for its growth, avoiding waste. The objective of this work was to characterize the behavior of capacitive sensors of humidity to monitor the moisture in the soils. In first instance, it was appraised sensors with dielectric built of synthetic pomes stone (Rd = 0,4 and Rd = 0,8) and of soil samples (Rd = 0,8 and Rd = 1,0), being the Rd parameter a geometric factor that relates the distance between the capacitor plates with radius of the plates. For the calibration, the sensors were installed in PVC recipient of cylindrical shape, filled with soil. The set (sensor and soil) was humidified by capillary effect and submitted by a natural drying very slowly. The parameter readings were taken daily, which allowed obtain the curves relating the humidity percentage, expressed in terms of dry weight, with the output voltage fort the sensor. The experiments were performed in sand soil and in dark red latossolo. The obtained results allowed to infer that the behavior of the sensor has a specific feature for each type of soil, being, therefore, necessary to develop a own calibration curve for the sensor, when used in soil with specific characteristic.