Higher Relative Growth Rate Research Articles

Relative growth rate, biomass partitioning and nutrient allocation in seedlings of two threatened trees grown under different light conditions

The present study investigates the variation in the relative growth, biomass and nutrient allocation in two threatened tree species viz. Magnolia punduana Hook.f. & Th. and Elaeocarpus prunifolius Wall. ex Müll. Berol. grown under three different levels of irradiance. The irradiance ranged between 1 and 12molm−2d−1. Results showed that the highest relative growth rate (RGR) was achieved under the intermediate light treatment for both the species (mean: 0.005mgmg−1d−1). The growth response coefficient (GRC) model revealed that net assimilation rate (NAR) was the factor driving the RGR in both species. A significant positive correlation was found between NAR and RGR (R2=0.33, p=0.000) whereas specific leaf area (SLA) and leaf mass fraction (LMF) was negatively correlated to RGR. Overall, multiple regression of the studied species based on the independent variables viz. NAR, SLA, and LMF showed a significant relation with RGR (F(3,50,53=13.001, p=0.000, R2=0.43). The biomass distribution in the studied species is in agreement with the “balanced-growth hypothesis” where high irradiance increased allocation to below ground biomass fraction and decreased irradiance increased allocation to the above ground fraction. The highest nitrogen concentration in leaves was observed under the intermediate light treatment. Overall seedlings growth under intermediate light had a higher mean RGR indicating the species' preference for partial light conditions. Long-term experiments under varied light conditions as in the present study would provide useful insight into plant growth strategies in varied environmental conditions.

Light energy partitioning, photosynthetic efficiency and biomass allocation in invasive Prunus serotina and native Quercus petraea in relation to light environment, competition and allelopathy

This study addressed whether competition under different light environments was reflected by changes in leaf absorbed light energy partitioning, photosynthetic efficiency, relative growth rate and biomass allocation in invasive and native competitors. Additionally, a potential allelopathic effect of mulching with invasive Prunus serotina leaves on native Quercus petraea growth and photosynthesis was tested. The effect of light environment on leaf absorbed light energy partitioning and photosynthetic characteristics was more pronounced than the effects of interspecific competition and allelopathy. The quantum yield of PSII of invasive P. serotina increased in the presence of a competitor, indicating a higher plasticity in energy partitioning for the invasive over the native Q. petraea, giving it a competitive advantage. The most striking difference between the two study species was the higher crown-level net CO2 assimilation rates (Acrown) of P. serotina compared with Q. petraea. At the juvenile life stage, higher relative growth rate and higher biomass allocation to foliage allowed P. serotina to absorb and use light energy for photosynthesis more efficiently than Q. petraea. Species-specific strategies of growth, biomass allocation, light energy partitioning and photosynthetic efficiency varied with the light environment and gave an advantage to the invader over its native competitor in competition for light. However, higher biomass allocation to roots in Q. petraea allows for greater belowground competition for water and nutrients as compared to P. serotina. This niche differentiation may compensate for the lower aboveground competitiveness of the native species and explain its ability to co-occur with the invasive competitor in natural forest settings.

Nitrogen Fertilization on Maize Sowing: Plant Growth and Seed Vigor

The management of fertilization in maize plants is a preponderant factor in the search for higher yields and obtaining quality seeds. In this sense, the study of nitrogen (N) management is predominant in improving the efficiency of its application. The objective of this study was to evaluate the growth, partition assimilation and vigor expression of maize seeds submitted at different doses of nitrogen applied at sowing. The treatments were constituted by different doses of nitrogen fertilization at sowing, being: 25%, 50%, 75% and 100% of the recommended dose for the crop, according to the recommendation of nitrogen fertilization. The plants were collected at regular intervals of 21 days after sowing until the end of the growth cycle. For the analysis of growth and partition of dry matter between the organs, the accumulation of dry matter and leaf area was measured. The experimental design was randomized blocks in a 4 × 7 factorial scheme (four N rates at sowing and seven collection times with three replications). The maize plants under the influence of nitrogen fertilization at sowing presented differential growth and distinct responses in the assimilated partition between their structures, with the intensity dependent on the dose used. Plants grown using 75% of the recommended dose of N at sowing had a higher relative growth rate, with more pronounced effects compared to the other doses. The expression of maize seed vigor increases to an increase of 82.5% N at sowing.

Influence of substrate orientation on tadpoles' feeding efficiency.

ABSTRACTIn nature, tadpoles encounter food on substrates oriented at different angles (e.g. vertically along stems, horizontally on the bottom of the pond). We manipulated the orientation of food-covered surfaces to test how different orientations of surfaces affect tadpoles' feeding efficiency. We studied taxa that differed in the oral morphology of their larvae and position in the water column. We hypothesized that species would differ in their ability to graze upon surfaces at different orientations and that differences in the tadpoles' feeding ability would result in different growth rates. The orientation of food-covered surfaces did not affect the growth rate of bottom-dwelling tadpoles (whose growth rate varied only between species). Among midwater tadpoles, some species appear to have a generalist strategy and experienced a high relative growth rate on numerous substrate orientations, whereas others achieved high growth rates only on flat substrates (i.e. at 0° and 180°). We conclude that oral morphology constrains tadpoles' ability to feed at different substrate orientations, and this could lead to niche partitioning in structurally complex aquatic environments. Because physical parameters of the environment can affect tadpoles' growth rate, characterizing these features might help us better understand how competition structures tadpole assemblages.

Recovery from short-term complete submergence in temperate pasture grasses

The ability to recover from the impact of short-term submergence was assessed on four widely used grasses in pastures: Dactylis glomerata L., Bromus catharticus Vahl., Schedonorus arundinaceus Schreb. (syn. Festuca arundinacea) and Phalaris aquatica L. Six-week-old plants were subjected to a 5-day complete submergence in clear water, followed by a 15-day recovery period. Dry mass after submergence, shoot and root growth, number of tillers per plant, leaf stomatal conductance and leaf greenness during recovery were assessed. Dactylis glomerata and B. catharticus were sensitive to submergence, showing very low relative growth rate (RGR) of shoots and roots during recovery (37–67% lower than controls) along with early leaf senescence and persistent partial stomatal closure. Schedonorus arundinaceus exhibited an intermediate tolerance, sustaining high RGR of shoots (similar to controls) and fully adjusting its leaf functionality during recovery despite being affected during submergence (40% decrease in dry mass and 37% in tiller number). Phalaris aquatica performed outstandingly, with dry mass unaffected by submergence, and unaltered stomatal conductance, leaf greenness, tillering and shoot growth during recovery. Therefore, in areas where flooding can often cause plant submergence, P. aquatica is recommended whereas the other species are not, because they may be outcompeted by flood-tolerant species.

Good Gardening for a Perennial Economy: What’s the Optimal Growth Path for a Regional Economy?

A key public policy issue in regional economic development is whether governments should act pro-actively with strategies to achieve local economic growth. Using an Australian region, this article presents projections that test a number of such scenarios to establish whether pro-active strategies of investment provide the greatest growth. When developing pro-active strategies for a given region, economic and community development planners typically target specific industries. Key industries can be identified on the basis of high relative employment growth rates and connectivity with other industries. The case region in this analysis, not unlike other regions in Australia and across the globe, has undergone significant restructuring in recent years with a shift in its economic base from agriculture to mining. In light of the shifting nature of the regional and national economies, this article provides a foundation for building planning perspectives for the future of a regional economy using economic and population projections and scenario analyses. These analyses help highlight industrial sectors that should be targeted in the region’s plans. Broader implications for regional economic development and planning generally are also drawn from the case experience. Developing projections for the growth of regional economies is no easy task. The complexities of inter-industry subsector interactions and the distinction between driving and adapting subsectors make formal modelling at the local level challenging and potentially prohibitive in terms of cost. These factors corroborate to make such bottom-up modelling beyond the capacity of most local organizations. By contrast, the approach used in this article is simple but requires care and intuition to bring these various factors together into a coherent set of projections. For the case region, optimal growth is possible provided that employment policy builds job specialization. This means directing strategies away from mining into agriculture and the trade and tourism related sectors, such as wine tourism. The economic base theory and scenario testing techniques used in this article demonstrate and deliver a useful contribution to the literature by exploring which industries contribute most to more diversified and sustainable growth. Through pre-emptive strategies, perennial growth of a regional economy can be achieved.

Salvinia molesta D.S. Mitch.

<i>Salvinia molesta</i> D.S. Mitch.

Weed ecology is affected by succession in differently aged gardens of Citrus sinensis and C. reticulata

The concepts of destruction and rebuilding in the succession play an important role in agro-ecology. Agricultural ecosystems are always affected by tillage, soil preparation, harvest, burning, and arboriculture. A common practice in the northern province of Mazandaran (Iran) is to replace rice (Oryza sativa L.) cultivation with Citrus farming. It can be accordingly interesting to investigate the ecology of weed community specifically the dominance and characters during the different stages of succession, using constitutive and physiological aspects. In a 2-year research work, some functional (species composition and stability) and physiological characteristics (relative growth rate, biomass, and N and P uptake) of different weeds in the initial and final stages of secondary succession in Citrus gardens were compared. Three young (Citrus sinensis L.) and three old Citrus (Citrus reticulata Blanco) gardens (with the average age of 2 and 29 years, respectively), were selected in the suburb of Qaemshahr city (Iran), the centre of Citrus production. In each garden, three main fixed plots (30 m2), with five subplots (1 m2) and destructive quadrates in each one, were prepared and used for the experiment (January 2013–August 2014). Weed composition was monthly recorded. The concept of dominance diversity was used to estimate the community consistency. Thirty-three weed species were identified among which the Poaceae and Asteraceae families were the dominant ones. In the young gardens, the number of weed species was twice more than the old ones. Poa nemoralis as a perennial and sciophytes species were plentiful in the old gardens. Just in the young gardens, the weed species were moved by pappus. There was a linear and stable regression between weed frequency and dominance in the final sampling. Higher relative growth rate as well as higher N and P uptake was resulted in the young gardens. Seed size and growth rate were correlated in the young gardens, and the smaller seeds resulted in a higher rate of weed survival. Parameters including weed dominance, functional and physiological characteristics, seed size, and the environment may determine weed ecology and survival at different stages of succession in Citrus gardens.

Microbial Solubilization of Rock Phosphate to Use in Sustainable Agriculture

Microbial solubiliztion is more environmentally sound method of modifying rock phosphate to use in sustainable agriculture as an alternative to chemical acidulation. Therefore, the present study was carried out to find the strategies for microbial solubilization of Eppawala rock phosphate with using biochar and microbial inoculants and effect of these on maize (Zea mays L.) growth and yield. A pot experiment was carried out in the plant house at Faculty of Applied Sciences, Rajarata University of Sri Lanka, Mihintale, during July to December 2015. After searching the literature the following ratios of biochar and RP were selected assuming that the better comparison obtained in different treatments. Treatments were comprised of T1: soil only, T2: sterilized soil and 3% RP, T3: soil and 3% RP, T4: soil, 20% biochar and 3% RP, T5: soil, mycorrhizae and 3% RP, T6: soil, Pseudomonas fluorescens and 3% RP, T7: soil, 20% biochar, mycorrhizae and 3% RP, T8: soil, 20% biochar, P. fluorescens and 3% RP, T9: soil, mycorrhizae, P. fluorescens and 3% RP, and T10: soil, 20% biochar, mycorrhizae, P. fluorescens and 3% RP. The treatments were arranged in a Completely Randomized Block Design (CRBD) with eight replicates. Maize was grown as a test plant. Growth parameters were recorded in four weeks intervals and relative growth rate was estimated. After 120 days of seeding, chemical characteristics and yield parameters were also measured. Results indicated that there was a significant difference among treatments (p<0.05) in all measured parameters over control. The highest available soil phosphorus was observed in biochar, mycorrhizae and P. fluorescens addition with 3% RP (T10) and highest leaf phosphorus was observed in biochar and mycorrhizae with 3% RP (T7). Significantly high (p<0.05) relative growth rate, numbers of leaves, length of leaves, shoot and root dry weights were observed in sterilized soil with 3% RP (T2). This higher growth and yield parameters of T2 may due to soil heating which increases certain soluble mineral nutrients availability. However, growth rate and yield were shown lower in biochar added treatments (T4, T7, T8 and T10). Short term influence of high amount of (20% v/v) biochar alone in plant growth and yield is less. It can be concluded that biochar, mycorrhizae and P. fluorescens are effective in solubilizing the high grade Eppawala rock phosphate. Further, microbial inoculants such as mycorrhizae and P. fluorescens increased the soil P availability and increased P nutrition, growth and yield of maize plants. Keywords: Rock phosphate, biochar, mycorrhizae, Pseudomonas fluorescens, phosphorus availability

Organic Fertilizers and Biofertilizers to Improve Growth, Yield and Nutrient Quality of Soybean (Glycine max L.)

Soybean (Glycine max L.) is one of the major legume crops cultivated in the dryzone of Sri Lanka. Most farmers use excess amounts of synthetic fertilizer to increase the yield of soybean and this causes serious health and environmental problems. Organic and biofertilizers can be used as an alternative, is a reliable solution for avoid the many of problems of synthetic fertilizer. The microbial consortium in the soil is critical to improve soil quality in agricultural fields. Organic residue recycling is becoming an increasingly important aspect of environmentally sound sustainable agriculture. Interactions of organic fertilizers with soil microorganisms are complex and improve the growth and yield of crops in tropical soil. The present study was conducted to find the effectiveness of organic and biofertilizers as an alternative to chemical fertilizer on growth yield and nutritional quality of soybean. A pot experiment was carried out in plant house at Faculty of Applied Sciences Mihintale, dryzone of Sri Lanka. Treatments were field soil only (T0), field soil and 5% biochar (T1), field soil and 5% cow dung (T2), field soil, 2.5% biochar and 2.5% cow dung (T3), field soil, 5% biochar and Bradyrhizobium (T4), field soil, 5% biochar and mycorrhizae (T5), field soil, 5% cow dung and Bradyrhizobium (T6) field soil, 5% cow dung and mycorrhizae (T7), field soil and synthetic fertilizer (T8), field soil, 2.5% cow dung 2.5% biochar and synthetic fertilizer (T9), field soil, 5% cow dung, mycorrhizae and Bradyrhizobium (T10), field soil, 5% biochar, mycorrhizae and Bradyrhizobium (T11). The treatments were tested in a Completely Randomized Block Design (CRBD) with six replicates. Considering the growth, significantly high (p<0.05) initial relative growth rate, number of leaflets, root dry weight, shoot dry weight, nodule dry weight was observed in T9, the addition of 2.5% cow dung, 2.5% biochar and synthetic fertilizer. Soybean yield such as number of pods and dry weight of 100 seeds were significantly high (p<0.05) in T10, the addition of field soil, 5% cow dung, mycorrhizae and Bradyrhizobium. Higher seed protein percentage was observed in T10, fat percentage in T4 and crude fiber percentage in T8 treatments. It can be concluded that yield and nutrient quality of soybean can be enhanced by the application of organic and biofertilizers together. This provides optimism for applying organic and biofertilizers on sustainable agricultural practices in dryzone of Sri Lanka. Keywords: Biofertilizers, Organic fertilizers, Glycine max, Growth, Yield, Nutrient quality

Cultivation of three color strains of Gracilaria domingensis in an integrated organic system

Species of the genus Gracilaria are widely distributed around the world, and many are wild harvested and cultivated for phycocolloid production (agar) and human food. This study investigated the growth performance of three color strains of Gracilaria domingensis in an integrated organic system. The three chromatic variants (red, green, and brown) were cultured in a shrimp farm at two depths (surface and 20 cm). The highest relative growth rates were obtained in the first week of cultivation for all three strains studied. Although the growth rates and biomass were slightly higher at a depth of 20 cm, significant differences were not observed at different depths (p < 0.05). The growth of the three strains varied significantly over time (p < 0.001). The maximal growth values obtained were 11.25 ± 1.50% day−1 (red), 12.76 ± 3.96% day−1 (green), and 7.86 ± 1.75% day−1 (brown). The mean growth rates for the whole period were 4.63 ± 6.97, 3.38 ± 9.09, and 2.16 ± 6.61% day−1 for the red, green, and brown strains, respectively. The pigment content (chlorophyll a, phycocyanin, and phycoerythrin) of the three strains studied was higher at a depth of 20 cm, while the maximum electron transport rate (ETRmax) and photosynthetic efficiency were higher at the surface. The high growth rates obtained in this study demonstrate the great potential of this species for integrated organic farming. Moreover, the ecological success shown by the red strain suggests that this strain is the most suitable for integrated cultivation.

Growth, phytochemicals, and optimal timing of planting Gracilariopsis persica: an economic red seaweed

A culture system for the commercial agarophyte seaweed Gracilariopsis persica has been developed, using long-line rope method in outdoor condition. Several environmental parameters of seawater at the cultivation site were recorded monthly over a year (December 2014 to November 2015). Relative growth rate (RGR) and its correlation with environmental parameters was investigated using Pearson correlations test. Phytochemical composition (moisture content, ash, protein, and lipid content) and agar yield quantity and quality (FTIR analysis of agar product) were studied during the cultivation period. We could grow the species only in 4 months of the year, December (2014) to March (2015), in outdoor conditions. The highest RGR (9.42% day−1) was obtained in February which was significantly different from the other months of growing period. Temperature, followed by nitrate and salinity, had significant effects on growth. RGR showed positive correlation with oxygen concentration and orthophosphate and negative correlations with temperature (r = −0.657), salinity (r = −0.607), and nitrate (r = −0.635). The yield of agar ranged from 26.7 to 33.7% with an average of 31.72% ± 0.18. FTIR analyses of agar product from Gp. persica showed similar FTIR patterns which mean that environmental conditions had no significant effect on the chemical structure. The range of moisture content (91.40–90.20%), ash (23–41% d.w.), protein (3.57–4.11% d.w.), and lipid (1.06–1.70% d.w.) showed the slight monthly significant difference in biochemical composition in the cultivated seaweed. These results indicated that Gp. persica can be successfully cultivated in the study area.

Ecophysiological responses of dual-purpose wheat originating from different cutting management systems

Wheat is one of the most cultivated cereals worldwide. Some wheat genotypes may be used for dual purposes that is, in the production of animal fodder and grains. The objective of this study was to compare the growth, partitioning of assimilates, and seed vigor expression of dual-purpose wheat cultivars originating from seeds produced by plants subjected to different cutting management systems. Dual-purpose wheat seeds in the vegetative period were used for this study; these were obtained from the cultivar BRS Umbu produced by plants subjected to different cutting management systems. The experimental design was completely randomized in a factorial scheme, with four replications. The treatments comprised a combination of four seed production systems (one, two, and three cuts) and eight planting seasons (10, 20, 30, 40, 50, 60, 70, and 80 days after emergence [DAE]). Total dry-mass, dry-mass production rate, relative growth rate, net assimilation rate, leaf area index, solar energy conversion efficiency, dry-mass partitioning, seedling emergence in the field, and emergence speed index were evaluated. Data regarding seedling emergence and emergence speed index were adjusted by orthogonal polynomials. Primary growth data were evaluated from the simple logistic equation. From 60 DAE, an inversion of the values of total dry-mass was observed, and the maximum values were observed in plants from seeds produced without cutting management. The highest dry-mass production rates were noted for plants produced by seeds of plants not subjected to cutting management. The highest relative growth rates were noted among plants originating from seeds produced by plants subjected to three- and two-cut treatments. The net assimilation rate was higher in plants originating from seeds produced from plants subjected to cutting management systems. The highest values of emergence were observed for seeds obtained from the three-cut treatment. Similarly, an increase in the values of emergence speed index was observed in seeds from plants subjected to one-cut treatment. Dual-purpose wheat cultivars originating from seeds produced in the absence of cutting management presented higher total dry-mass, dry-mass production rate, and relative growth rate. The net assimilation rate was higher in plants from seeds produced with cutting management systems. Plants produced from seeds subjected to the three-cut production management resulted in more vigorous seeds.

Morpho-functional traits and plant response to drought conditions in seedlings of six native species of Ecuadorian Ecosystems

Tropical Andean ecosystems have been identified as very vulnerable to climate change. Changes in climatic conditions, especially drought as envisaged by climate change projections, could affect the establishment of new individuals that are responsible for ensuring the persistence of species and plant communities. The aim was to study the main morpho-functional traits related to water use and drought resistance of native plant species from Ecuadorian ecosystems during imposed drought periods. Seedlings of six native species representative of the Ecuadorian Andes were studied: lower montane evergreen forest (Alnus acuminata and Cedrela montana), montane cloud forest (Podocarpus sprucei and Aegiphila ferruginea) and montane dry shrubland (Schinus molle and Caesalpinia spinosa). Morphological characterisation, a root growth capacity test and stomatal conductance measurements during two controlled drought periods were used to investigate biomass allocation patterns, the root system morphology and gas exchange patterns of species, respectively. The main results indicated that species-specific differences in morpho-functional traits and allocation patterns determined responses to water availability and drought conditions. Low relative growth rate, leaf area ratio and specific leaf area, and high specific root length, were related to drought-resistant species as P. sprucei and C. spinosa. In contrast, a high or moderate relative growth rate, leaf area and root biomass, but low specific root length as in A. ferruginea, S. molle, C. montana, were related to lower resistance to drought conditions. Despite A. acuminata showed high specific root length, it was reported as a species sensitive to drought. Overall, patterns of stomatal conductance, linked to biomass allocation patterns and root system morphology, especially specific root length, seemed to be related to differences in vulnerability to drought in these species. Drought response was independent of species habitats. Unexpectedly, P. sprucei, belonging to montane cloud forest showed higher drought resistance than S. molle, belonging to montane dry shrubland.

Growth and nutrient removal of three macrophytes in response to concentrations and ratios of N and P

ABSTRACTWastewater from different sources shows great differences in concentrations and ratios of N and P. In order to choose suitable plant species to remove excess N and/or P from polluted waters, it is important to know the performances of these plants under different N and P concentrations. In this study, we investigated the growth and N and P removal rate of three macrophytes, Coix lacryma-jobi, Iris wilsonii, and Arundo donax under six N and P combination treatments. C. lacryma-jobi preferred higher N and P concentrations (16 mg N L−1 and 3.2 mg P L−1), and increasing N supply could increase its P removal rate. I. wilsonii exhibited a growth preference at a combination of moderate N and P concentrations (8 mg N L−1 and 0.8 mg P L−1). A. donax could grow well at all combinations of N and P and had significantly higher relative growth rate and N and P removal rates than the other two species. These results showed A. donax is a promising species to treat various polluted waters and the other two species can be used specifically to treat certain types of wastewater.

Similarity of plant functional traits and aggregation pattern in a subtropical forest.

The distribution of species and communities in relation to environmental heterogeneity is a central focus in ecology. Co‐occurrence of species with similar functional traits is an indication that communities are determined in part by environmental filters. However, few studies have been designed to test how functional traits are selectively filtered by environmental conditions at local scales. Exploring the relationship between soil characteristics and plant traits is a step toward understanding the filtering hypothesis in determining plant distribution at local scale. Toward this end, we mapped all individual trees (diameter >1 cm) in a one‐ha subtropical forest of China in 2007 and 2015. We measured topographic and detailed soil properties within the field site, as well as plant leaf functional traits and demographic rates of the seven most common tree species. A second one‐ha study plot was established in 2015, to test and validate the general patterns that were drawn from first plot. We found that variation in species distribution at local scale can be explained by soil heterogeneity and plant functional traits. (From first plot). (1) Species dominant in habitats with high soil ammonium nitrogen and total phosphorus tended to have high specific leaf area (SLA) and relative growth rate (RGR). (2) Species dominant in low‐fertility habitats tended to have high leaf dry matter content (LDMC), ratio of chlorophyll a and b (ratioab), and leaf thickness (LT). The hypothesis that functional traits are selected in part by environmental filters and determine plant distribution at local scale was confirmed by the data of the first plot and a second regional site showed similar species distribution patterns.

Post-fire resprout in an endangered and narrow endemic shrub from rupestrian grasslands, Serra do Cipó, southeastern Brazil

Although there is evidence that the vegetation from rupestrian grasslands is resilient to fire, investigations about the effects of increasing frequency of anthropogenic fires in the rare and endemic plants from this ecosystem are still incipient. In this study, we monitored the post-fire resprouting of the endemic and endangered shrub species Coccoloba cereifera Schwacke (Polygonaceae) from rupestrian grasslands, southeastern Brazil. Five months after the fire 100% of the monitored individuals resprouted. However, one year after the fire, the burned plants had the ramet length 24% lower and number of leaves 53.5% smaller in relation to unburned plants. Burned plants showed a much higher relative growth rate in number of leaves and much lower reproductive investment compared to unburned plants. Although the studied species showed a high ability to resprout after fire, the pattern of vegetative growth and reproductive investment showed by the burned plants suggested that the increasing frequency of anthropogenic fires represents a serious threat to C. cereifera.Keywords: Coccoloba cereifera, conservation, Espinhaco Range, plant growth, reproductive phenology.

Effects of polycaprolactone coating on the biodegradable behavior and cytotoxicity of Mg-6%Zn-10%Ca3(PO4)2 composite in simulated body fluid

Mg-6%Zn-10%Ca3(PO4)2 composite was prepared through powder metallurgy methods with polycaprolactone(PCL) coating on its surface. The properties of the PCL coatings on the surface of Mg-6%Zn-10%Ca3(PO4)2 composite, such as surface morphology, the corrosion behavior and the cytotoxicity properties were investigated. The results show that PCL coating improves the corrosion resistance of the magnesium matrix composite specimens significantly. Mg-6%Zn-10%Ca3(PO4)2 composite specimens with PCL coating exhibit good corrosion resistance and low pH values in SBF at 37°C in the immersion test, as compared with uncoated specimens. The cytotoxicity tests indicate Mg-6%Zn-10%Ca3(PO4)2 with PCL coating is nontoxic with higher relative growth rate than that of uncoated composites against L-929 cells.

Major shifts in species’ relative abundance in grassland mixtures alongside positive effects of species diversity in yield: a continental‐scale experiment

SummaryIncreased species diversity promotes ecosystem function; however, the dynamics of multi‐species grassland systems over time and their role in sustaining higher yields generated by increased diversity are still poorly understood. We investigated the development of species’ relative abundances in grassland mixtures over 3 years to identify drivers of diversity change and their links to yield diversity effects.A continental‐scale field experiment was conducted at 31 sites using 11 different four‐species mixtures each sown at two seed abundances. The four species consisted of two grasses and two legumes, of which one was fast establishing and the other temporally persistent. We modelled the dynamics of the four‐species mixtures, and tested associations with diversity effects on yield.We found that species’ dynamics were primarily driven by differences in the relative growth rates (RGRs) of competing species, and secondarily by density dependence and climate. The temporally persistent grass species typically had the highestRGRs and hence became dominant over time. Density dependence sometimes induced stabilising processes on the dominant species and inhibited shifts to monoculture. Legumes persisted at most sites at low or medium abundances and persistence was improved at sites with higher annual minimum temperature.Significant diversity effects were present at the majority of sites in all years and the strength of diversity effects was improved with higher legume abundance in the previous year. Observed diversity effects, when legumes had declined, may be due to (i) important effects of legumes even at low abundance, (ii) interaction between the two grass species or (iii) a store of N because of previous presence of legumes.Synthesis. Alongside major compositional changes driven byRGRdifferences, diversity effects were observed at most sites, albeit at reduced strength as legumes declined. This evidence strongly supports the sowing of multi‐species mixtures that include legumes over the long‐standing practice of sowing grass monocultures. Careful and strategic selection of the identity of the species used in mixtures is suggested to facilitate the maintenance of species diversity and especially persistence of legumes over time, and to preserve the strength of yield increases associated with diversity.

The use of size and growing height to improve Crassostrea gigas farming and breeding techniques against OsHV-1

Mortality associated with ostreid herpesvirus 1 (OsHV-1) has significantly impacted Crassostrea gigas farmers all around the world. Although selective breeding programs to improve OsHV-1 resistance can significantly reduce the mortality rate below 20%, husbandry practices have also been one way to limit or decrease mortality. The main objectives of this study were to describe the influence of two husbandry practices on OsHV-1-induced mortality in C. gigas spat and how different family lines respond to husbandry practices to gain a better understanding of the potential benefits of breeding management as a tool to adapt to improved practices. The first analysis investigated the importance of the size of C. gigas when challenged with OsHV-1 for the first time. For each of the 40 families of C. gigas evaluated, small (S) and large (L) oyster groups were tested for two years in the field. A significant mortality outbreak associated with OsHV-1 occurred during the first spring. At the end of the trial, the mean cumulative mortality of the L group (54.1%) was significantly lower than the mean cumulative mortality of the S group (74.8%), indicating the importance of size in OsHV-1-associated mortality. However, the overall effect of size was not consistent for all families: in 11 of the 40 families tested, there appeared to be no difference in mortality between the S and L groups. Observations at the family level allowed the identification of a large range of susceptibility to OsHV-1 regardless of the size group, with highly resistant families (<32%) and highly susceptible families (>80%). The second investigation compared different growing heights. Each of the 40 families was grown at three heights (high Hi, medium Me, and low Lo) corresponding to mean emersion times of 25, 12 and 2%, respectively. After an OsHV-1-related mortality outbreak, the mean mortality among the families was 91.6%, 88.0% and 86.9% for the Lo, Me and Hi conditions, respectively. Growing height had no effect in 31 of the 40 families tested, and these families showed no potential for adaptation to improve growing height practices. Among them, 24 families showed extremely high mortality (>95%) and 2 families showed the lowest mortality (<40%). In contrast, nine families showed differences in mortality associated with growing heights. A tendency toward higher mortality was observed for oysters that emerged less, with 85% for Lo compared to 72% for Hi. A protective effect of a high growing height on spat oysters was confirmed. In both experiments, higher relative growth rates were associated with higher mortality by OsHV-1. Finally, we identified oyster families from the two husbandry practices that were resistant or susceptible to OsHV-1 infection regardless of their size, growing height and age. Finally, a moderate heritability of mortality, ranging from 0.44 to 0.49, was determined from the size investigation.Statement of relevanceHusbandry practices can decrease OsHV-1 mortality in C gigas, but it depends on the genetic resistance of the oyster stocks used.