Faster Plant Growth Research Articles

Pelatihan Hidroponik Sistem Sederhana pada Skala Rumah Tangga di Desa Salo, Kecamatan Salo, Kabupaten Kampar, Riau

Public knowledge about health, the dangers of pesticides, environmentally friendly issues, make hydroponic vegetables are starting to be in deman. The increase in consumption of hydroponic vegetables provides a great opportunity for hydroponic vegetable businesses. The hydroponic system has many advantages compared to conventional systems,like environmentally friendly, hygienic and healthy products, faster plant growth, the quality of plant yields can be maintained and the quantity can be increased. The Community Service Team (PKM) has conducted a field survey and communication with the Salo Village regarding the problems they face. An agreement has been reached and a PKM program has been approved in the form of guidance and training on the hydroponic agricultural technology system on a household scale in Salo Village, Salo District, Kampar Regency, Riau. The extension material includes what is hydroponic cultivation, the importance of hydroponic cultivation for improving the family economy and various hydroponic media from simple materials. The team presents a 9-hole hydroponic system, hydroponics, seeds and plant nutrients. The vegetable seeds given are lettuce. The reason for choosing lettuce is because lettuce has high economic value, is more resistant to pests, has many types of variants, and is good for health. The condition of the residents of Salo Village has great potential for empowerment. The active participation of the residents of Salo Village to participate in counseling and hydroponic planting practices shows that the enthusiasm of the residents is very high. The activeness shown by participating in direct practice shows that there is additional knowledge and understanding of residents about hydroponics. This community service activity went succesfully and was achieved according to plan. Kata Kunci: Hidroponik, selada, penyuluhan

Evaluation of Stevia rebaudiana Leaf-Axillary Shoot Formation, Cultured in MS Medium Supplemented with IAA-BAP and MS Medium Supplemented with Kinetin

Stevia rebaudiana leaves can be used as a sweetener alternatives because they contain steviol glycoside derivative compounds, including steviosides and rebaudioside-A. Propagation of Stevia is more optimally carried out using in vitro culture when compared to conventional propagation through seeds or cuttings. This study aimed to evaluate the formation and growth of Stevia shoots and leaves in MS medium containing a mixture of IAA and BAP with MS medium containing kinetin only, as well as evaluating the use of a liquid medium containing kinetin. Stevia was initiated from apical shoot then grown in MS medium containing a mixture of IAA and BAP with MS medium containing kinetin only. Stevia was subcultured every 4 weeks. Several parameters measured were number of axillary shoots and number of leaves. It was transferred into a liquid medium for 7 days. The results showed that the formation and growth of axillary buds and leaves at the initiation stage were better in medium containing IAA and BAP compared to medium containing single hormone kinetin. At the stage of shoot multiplication and maintenance, cultivation in semi-solid medium containing kinetin showed more leaves and axillary shoots compared to that cultivated in semi-solid medium with the addition of IAA and BAP. Plants acclimatized in liquid medium supplemented with 1 ppm kinetin showed fast plant growth but were not accompanied by sturdy stem growth. The presence of brownish color on certain parts of the plant such as in some leaves and stems was also observed.

High Efficiency Regeneration System from Blueberry Leaves and Stems.

The main propagation approach is tissue culture in blueberries, and tissue culture is an effective and low-cost method with higher economic efficiency in blueberries. However, there is a lack of stable and efficient production systems of industrialization of tissue culture in blueberries. In this study, the high-efficiency tissue culture and rapid propagation technology system were established based on blueberry leaves and stems. The optimal medium for callus induction was WPM (woody plant medium) containing 2.0 mg/L Forchlorfenuron (CPPU), 0.2 mg/L 2-isopentenyladenine (2-ip) with a 97% callus induction rate and a callus differentiation rate of 71% by using blueberry leaves as explants. The optimal secondary culture of the leaf callus medium was WPM containing 3.0 mg/L CPPU with an increment coefficient of 24%. The optimal bud growth medium was WPM containing 1.0 mg/L CPPU, 0.4 mg/L 2-ip, with which the growth of the bud was better, stronger and faster. The optimal rooting medium was 1/2 Murashige and Skoog (1/2MS) medium containing 2.0 mg/L naphthylacetic acid (NAA), with which the rooting rate was 90% with shorter rooting time and more adventitious root. In addition, we established a regeneration system based on blueberry stems. The optimal preculture medium in blueberry stem explants was MS medium containing 2-(N-morpholino) ethanesulfonic acid (MES) containing 0.2 mg/L indole-3-acetic acid (IAA), 0.1 mg/L CPPU, 100 mg/L NaCl, with which the germination rate of the bud was 93%. The optimal medium for fast plant growth was MS medium containing MES containing 0.4 mg/L zeatin (ZT), 1 mg/L putrescine, 1 mg/L spermidine, 1 mg/L spermidine, which had a good growth state and growth rate. The optimal cultivation for plantlet growth was MS medium containing MES containing 0.5 mg/L isopentene adenine, with which the plantlet was strong. The optimal rooting medium for the stem was 1/2MS medium containing 2.0 mg/L NAA, with which the rooting rate was 93% with a short time and more adventitious root. In conclusion, we found that stem explants had higher regeneration efficiency for a stable and efficient production system of industrialization of tissue culture. This study provides theoretical guidance and technical support in precision breeding and standardization and industrialization in the blueberry industry.

Aloe vera Rind Valorization to Improve the Swelling Capacity of Commercial Acrylic Hydrogels

Acrylic hydrogels have been used in agriculture to increase the availability of water in the soil; cause faster plant growth and increase plant survival to water stress; allow controlled release of fertilizers; and, therefore, increase crop yields. On the other hand, Aloe vera gel production generates a large amount of solid waste as cuticles, which is currently underutilized despite that it is a good source of cellulose nanofibers that could be used to improve the swelling capacity of commercial acrylic hydrogels. In this work, both morphology (SEM) and particle size (TEM) of the cellulose nanofibers obtained from A. vera cuticles by the acid hydrolysis method combined with ultrasound were analyzed; as well as the presence of functional groups (FITR) and thermal stability (TGA). Then, acrylic hydrogels were synthesized by the solution polymerization method, and nanofibers were added to these hydrogels at different concentrations (0% w w−1, 3% w w−1, 5% w w−1, and 10% w w−1). These concentrations had a nonlinear relationship with the swelling capacity, and the hydrogel reinforced at 3% cellulose nanofiber was chosen as the best formulation in this work, as this one improved the swelling capacity of hydrogels at equilibrium (476 g H2O g hydrogel−1) compared to the hydrogel without nanofiber (310 g H2O g hydrogel−1), while hydrogels with 10% nanofiber had a similar swelling capacity to the non-reinforced hydrogel (295 H2O g hydrogel−1). Therefore, cellulose-based superabsorbent hydrogels with potential application in agriculture were developed in this work.

Expression of a carotenogenic gene allows faster biomass production by redesigning plant architecture and improving photosynthetic efficiency in tobacco.

Because carotenoids act as accessory pigments in photosynthesis, play a key photoprotective role and are of major nutritional importance, carotenogenesis has been a target for crop improvement. Although carotenoids are important precursors of phytohormones, previous genetic manipulations reported little if any effects on biomass production and plant development, but resulted in specific modifications in carotenoid content. Unexpectedly, the expression of the carrot lycopene β-cyclase (DcLCYB1) in Nicotiana tabacum cv. Xanthi not only resulted in increased carotenoid accumulation, but also in altered plant architecture characterized by longer internodes, faster plant growth, early flowering and increased biomass. Here, we have challenged these transformants with a range of growth conditions to determine the robustness of their phenotype and analyze the underlying mechanisms. Transgenic DcLCYB1 lines showed increased transcript levels of key genes involved in carotenoid, chlorophyll, gibberellin (GA) and abscisic acid (ABA) biosynthesis, but also in photosynthesis-related genes. Accordingly, their carotenoid, chlorophyll, ABA and GA contents were increased. Hormone application and inhibitor experiments confirmed the key role of altered GA/ABA contents in the growth phenotype. Because the longer internodes reduce shading of mature leaves, induction of leaf senescence was delayed, and mature leaves maintained a high photosynthetic capacity. This increased total plant assimilation, as reflected in higher plant yields under both fully controlled constant and fluctuating light, and in non-controlled conditions. Furthermore, our data are a warning that engineering of isoprenoid metabolism can cause complex changes in phytohormone homeostasis and therefore plant development, which have not been sufficiently considered in previous studies.

Identification of Acetoin Producing Rhizobacteria as Rice Plant Growth Control (Oryza sativa) from The Rhizosphere of Elephant Grass Plant (Pennisetum purpureum) using Gas Chromatography Mass Spectrometry (GC-MS) and Scanning Electron Microscope (SEM)

The compound of acetoin (3-hydroxybutan-2-butanone) is a volatile compound produced by bacteria that functions as a booster for plant growth or as a biostimulant. Acetoin plays an important role in stimulating the process of organogenesis (morphogenesis) plants so that the formation of plant organs faster and faster plant growth. Besides being able to increase the growth of acetoin, it can also induce plant resistance, increase the formation of branches, roots and flowers so that acetoin can increase plant productivity. The purpose of this study was to identify acetoin-producing rhizobacteria which can stimulate rice growth. Identification of compounds was carried out using Gas Chromatography Mass Spectrometry (GC-MS) and Scanning Electron Microscope (SEM). This study obtained one rhizobacterial isolate capable of producing acetoin which acts as a plant growth booster, namely Rg21. This rhizobacterial isolate was able to increase the number of lateral roots of rice seedlings at the age of 14 days after plants with a percentage increase of 50.00% when compared to controls.

PENGARUH PUPUK ORGANIK DAN BATUAN FOSFAT ALAM PADA INCEPTISOL SEBAGAI MEDIA TANAM TERHADAP PERBANYAKAN MIKORIZA ARBUSKULA (MA) DENGAN BERBAGAI TANAMAN INANG

The distribution of very abundant AM in UB forest is very potential to be used as biological fertilizer. Biofertilizer production through the utilization of AM spores requires the multiplication of AM by using host plants namely maize (Zea mays L.), soybean (Glycine max (L) Merill) and tithonia (Tithonia diversifolia) and planting media consisting of soil added with cattle manure and rock phosphate. This study aimed to obtain the best host plants and growing media in producing the number of AM spores and AM colonies so that they can be used as AM biological fertilizer production. The study design used was a factorial randomized group design with host plants (H) as the first factor and planting media (M) as the second factor consisting of 18 treatments with 3 replications. The multiplication results showed that media with an M5 dose (150 kg ha-1 rock phosphate + 5 t ha-1 cattle manure) was high in producing AM spores amounting to 324,67 AM 100 g soil-1 in maize and 61.11% AM colonies in soybeans. Rock phosphate and cattle manure were sources of P in the growing media and AM which was multiplied to carry out its activities in producing phosphatase enzymes to produce P available for plants. Maize and soybeans had stable growth, good rooting, fast plant growth and low root lignin content which made it easy for AM to make colonies.

Wood chip soil amendments in restored wetlands affect plant growth by reducing compaction and increasing dissolved phenolics

Adding chipped wood to soil ameliorates compaction, allowing faster plant growth that is critical to successful wetland restorations. Following the filling and planting of an erosion gully in Halstead Meadow, Sequoia National Park, the tallest leaf height and maximum clone width of transplanted Scirpus microcarpus seedlings were negatively correlated with soil compaction. Plant height decreased by 9.8 cm and width decreased by 11.9 cm per MPa of soil compaction (range of 0.74–4.50 MPa). We experimentally amended mineral soil in a test trench and found that every 0.10 cm3/cm3 addition of wood chips (range of 0.00–0.75 cm3/cm3) reduced compaction by 0.174 MPa. Had the Halstead Meadow gully fill contained an equivalent volume of wood chips to the reference area soil organic matter content (0.64 cm3/cm3), we predict compaction would have been reduced by 1.11 MPa, increasing individual transplant width spread by 36%, approximately doubling the vegetated area after two growing seasons. In a greenhouse phytometer experiment, conifer bark leachate (phenolics 211 mg/L) significantly reduced plant growth and, in the presence of added nutrients, increased the production of the enzyme polyphenol oxidase (PPO). However, phenolics concentration in bark‐free conifer wood leachate (12 mg/L), similar to field‐sampled concentrations, did not affect plant growth or PPO production. Pure conifer bark is not recommended as a soil amendment, but the addition of low‐bark‐content wood chips to gully fill may be a feasible and effective means of reducing soil compaction, accelerating plant establishment, and lowering wetland restoration project costs.

Growth and physiology of the citrange ‘Fepagro C37 Reck’ rootstock innoculated with arbuscular mycorrhizal fungi

ABSTRACT The use of arbuscular mycorrhizal fungi (AMF) in the production of rootstocks is a strategy to promote faster plant growth. However, this response depends on the symbiont species. The objective of this study was to evaluate the influence of different species of arbuscular mycorrhizal fungus (AMF) on the development and physiology of citrange 'Fepagro C37 Reck' rootstock. Four species of AMF were used in the experiment: Scutellospora heterogama, Gigaspora margarita, Glomus etunicatum, and Acaulospora sp., and a control treatment. The experiment was arranged in a randomized blocks design, with 5 treatments, 3 replicates, and 10 plants per plot. Every 15 days, height (cm) and stem diameter (mm) of plants were measured in the nursery. At 330 days, the number of leaves, leaf area (cm²), fresh and dry mass of roots and shoot (g/plant), root and shoot reserve content, and AMF colonization were evaluated. The AMF inoculation promoted an accelerated vegetative growth, resulting in greater height and diameter. The fungi also promoted greater absorption of most of the nutrients and increase in all other parameters evaluated. However, no effect was found on the reserve content of the rootstock. Roots were colonized with moderate presence of arbuscules and low presence of vesicles. AMF, regardless of species, influence the development and physiology of the citrange 'Fepagro C37 Reck' rootstock.

A new bioenergy crop based on oil-rich seeds from the legume tree <em>Pongamia pinnata</em>

A new bioenergy crop based on oil-rich seeds from the legume tree Pongamia pinnata Peter M Gresshoff,1 Latha Rangan,2 Arief Indrasumunar,1 Paul T Scott11Centre for Integrative Legume Research, School of Agriculture and Food Sciences, The University of Queensland, St Lucia, Brisbane, QLD, Australia; 2Department of Biosciences and Bioengineering, Indian Institute of Technology Guwahati, Assam, India Abstract: Any informed discussion on the future sources of energy in our world requires the consideration of renewable biofuels. These are produced by biological processes, such as plant growth based on photosynthesis and microbes using waste products from diverse origins. Many biofuels, such as ethanol produced from plants like sugarcane, are seen as sustainable, such paradigms should be critically analyzed in terms of total inputs. The legume tree Pongamia pinnata (also called Millettia pinnata) offers a substantiated opportunity for a sustainable biofuel feedstock. It is characterized by fast plant growth, broad tropical and subtropical growth habitat, and high annual yields of oil-rich seed. Annual yield of the seed-extracted oil, rich in the monounsaturated fatty acid oleic acid (C18:1), is between 1,000 and 5,000 L/ha, depending on local conditions, including rainfall, temperature, and soil. It can be burnt in bioenergy generators to yield electrical output. It can also be converted to biodiesel by transesterification for transportation and industrial use. Conversion to aviation jet fuel by hydrogenation and subsequent purification is also possible. The legume nature of the plant allows it to harbor nitrogen-fixing soil bacteria (broadly called “rhizobia”) in newly induced root organs called nodules. This symbiosis makes the energy inputs considerably less than those seen with nitrate fertilizer – requiring biofuel feedstocks, such as corn, sugarcane, and canola. Combined with general characteristics of plant, such as abundant seed set and large oil-rich seed, secondary products, such as seed meal and vigorous growth characteristics, make this tree an excellent candidate for sustainable bioenergy production in many parts of the globe. Keywords: biofuel, biotechnology, legume, plant growth, renewables, sustainability

Ecotoxicological assessment of biosolids by microcosms

Biosolids have been applied as soil amendments to improve and maintain the soil fertility and faster plant growth. In spite of its beneficial use, the potential risks of land disposal should be analyzed, considering potential ecological receptors in soil and water. This work describes the use of an early warning laboratory microcosm system to evaluate the integrated ecotoxicological potential of two biosolids: BIO-1 and BIO-2 (18 and 28 months after landfarming, respectively), from an effluent treatment station in a petrochemical and industrial district. The endpoints related to habitat function were: a) germination, growth and biomass of Phaseolus vulgaris; b) survival, biomass and number of cocoons of Eisenia andrei (Oligochaeta) and; c) reproduction of Folsomia candida (Collembola). The retention function was evaluated by testing the leachates using the tropical cladoceran Latonopsis australis (Cladocera) in a 48-h acute toxicity test, and growth of the aquatic plant Lemna minor in a 7-d chronic test. Tropical artificial soil (TAS) and a natural soil (NS) from the region were used as control soils. Results showed no chronic toxicity of BIO-1 and BIO-2 to the soil organisms tested, but acute toxicity of BIO-1 in the leachate for 50% of L. australis, and chronic toxicity of both biosolid leachates to L. minor (inhibition of growth rate), indicating potential risks to aquatic ecosystems. The results confirmed the ability of this microcosm system as a rapid tool to assess biosolid toxicity over time and its potential for hazardous waste characterization in environmental risk assessment, in a screening phase.

Heterologous expression of chloroplast-localized geranylgeranyl pyrophosphate synthase confers fast plant growth, early flowering and increased seed yield.

SummaryGeranylgeranyl pyrophosphate synthase (GGPS) is a key enzyme for a structurally diverse class of isoprenoid biosynthetic metabolites including gibberellins, carotenoids, chlorophylls and rubber. We expressed a chloroplast‐targeted GGPS isolated from sunflower (Helianthus annuus) under control of the cauliflower mosaic virus 35S promoter in tobacco (Nicotiana tabacum). The resulting transgenic tobacco plants expressing heterologous GGPS showed remarkably enhanced growth (an increase in shoot and root biomass and height), early flowering, increased number of seed pods and greater seed yield compared with that of GUS‐transgenic lines (control) or wild‐type plants. The gibberellin levels in HaGGPS‐transgenic plants were higher than those in control plants, indicating that the observed phenotype may result from increased gibberellin content. However, in HaGGPS‐transformant tobacco plants, we did not observe the phenotypic defects such as reduced chlorophyll content and greater petiole and stalk length, which were previously reported for transgenic plants expressing gibberellin biosynthetic genes. Fast plant growth was also observed in HaGGPS‐expressing Arabidopsis and dandelion plants. The results of this study suggest that GGPS expression in crop plants may yield desirable agronomic traits, including enhanced growth of shoots and roots, early flowering, greater numbers of seed pods and/or higher seed yield. This research has potential applications for fast production of plant biomass that provides commercially valuable biomaterials or bioenergy.

Photosynthesis-dependent physiological and genetic crosstalk between cold acclimation and cold-induced resistance to fungal pathogens in triticale (Triticosecale Wittm.)

The breeding for resistance against fungal pathogens in winter triticale (Triticosecale Wittm.) continues to be hindered by a complexity of the resistance mechanisms, strong interaction with environmental conditions, and dependence on the plant genotype. We showed, that temperature below 4°C induced the plant genotype-dependent resistance against the fungal pathogen Microdochium nivale. The mechanism involved, at least, the adjustment of the reactions in the PSII proximity and photoprotection, followed by an improvement of the growth and development. The genotypes capable to develop the cold-induced resistance, showed a higher maximum quantum yield of PSII and a more efficient integration of the primary photochemistry of light reactions with the dark reactions. Moreover, induction of the photoprotective mechanism, involving at least the peroxidases scavenging hydrogen peroxide, was observed for such genotypes. Adjustment of the photosynthesis and stress acclimation has enabled fast plant growth and avoidance of the developmental stages sensitive to fungal infection. The same mechanisms allowed the quick regrow of plants during the post-disease period. In contrast, genotypes that were unable to develop resistance despite cold hardening had less flexible balancing of the photoprotection and photoinhibition processes. Traits related to: photosynthesis-dependent cold-acclimation and cold-induced resistance; biomass accumulation and growth; as well as protection system involving peroxidases; were integrated also at a genetic level. Analysing 95 lines of the mapping population SaKa3006×Modus we determined region on chromosomes 5B and 7R shared within all tested traits. Moreover, similar expression pattern of a set of the genes related to PSII was determined with the metaanalysis of the multiple microarray experiments. Comparable results for peroxidases, involving APXs and GPXs and followed by PRXs, indicated a similar function during cold acclimation and defense responses. These data provide a new insight into the cross talk between cold acclimation and cold-induced resistance in triticale, indicating a key role of photosynthesis-related processes.

Distinct responses of the mitochondrial respiratory chain to long‐ and short‐term high‐light environments in Arabidopsis thaliana

In order to ensure the cooperative function with the photosynthetic system, the mitochondrial respiratory chain needs to flexibly acclimate to a fluctuating light environment. The non-phosphorylating alternative oxidase (AOX) is a notable respiratory component that may support a cellular redox homeostasis under high-light (HL) conditions. Here we report the distinct acclimatory manner of the respiratory chain to long- and short-term HL conditions and the crucial function of AOX in Arabidopsis thaliana leaves. Plants grown under HL conditions (HL plants) possessed a larger ubiquinone (UQ) pool and a higher amount of cytochrome c oxidase than plants grown under low light conditions (LL plants). These responses in HL plants may be functional for efficient ATP production and sustain the fast plant growth. When LL plants were exposed to short-term HL stress (sHL), the UQ reduction level was transiently elevated. In the wild-type plant, the UQ pool was re-oxidized concomitantly with an up-regulation of AOX. On the other hand, the UQ reduction level of the AOX-deficient aox1a mutant remained high. Furthermore, the plastoquinone pool was also more reduced in the aox1a mutant under such conditions. These results suggest that AOX plays an important role in rapid acclimation of the respiratory chain to sHL, which may support efficient photosynthetic performance.

Integrating Photosynthesis, Respiration, Biomass Partitioning, and Plant Growth: Developing a Microsoft Excel®-based Simulation Model of Wisconsin Fast Plant (Brassica rapa, Brassicaceae) Growth with Undergraduate Students

This paper demonstrates the development of a simple model of carbon flow during plant growth. The model was developed by six undergraduate students and their instructor as a project in a plant ecophysiology course. The paper describes the structure of the model including the equations that were used to implement it in Excel®, the plant growth experiments that were conducted to obtain information for parameterizing and testing the model, model performance, student responses to the modeling project, and potential uses of the model by other students.

China–U.S. workshop on biotechnology of bioenergy plants

The China and U.S. economies are the globally dominantdrivers of fossil fuel consumption and release of green-house gases and are thus strategically linked to the sus-tainable development of sustainable, alternative, andrenewable energy sources. Because of the dynamics andspatial interdependence between human activities andnatural ecosystems, a major challenge arises: how tooperate a renewable-energy economy within the ecologicalconstraints of the biosphere. Renewable energy utilizesbio-based energy technology and other renewable sourcesas a substitute for fossil fuels. Although current levels andtypes of pollution associated with our present energy useswill decline, renewable energy technologies will introducenew environmental challenges that at present are onlypartly understood or defined. Therefore, a strategy is nee-ded to address the uncertainty of these new activities, whileattempting to protect natural ecological processes in orderto sustain biological resources. Thus, we presume that thecombination of more intensive growth of agriculture andthe production of bioenergy plants coupled with moresustainable management practices is an end goal worthy ofscientific pursuit. The biotechnology of bioenergy plantswill be an important component of this strategy as fasterplant growth, pest resistance, and many other plant char-acteristics that will be required to meet these goals, manyof which cannot be achieved in a reasonable time frame viaconventional breeding.China and the U.S. are natural partners for the devel-opment of biofuel technologies. Although there are dif-ferences in some aspects of their agriculture, naturalresources, economy, and society, the two nations sharemany interests with respect to the environment, climatechange, and scientific pursuits. In both the U.S. and China,it is hoped that the emerging bioenergy industry will giverise to a robust new rural economy in which ethanoland other biofuel and bioproduct production will meet

Sediment type, population density and their combined effect greatly charge the short-time growth of two common submerged macrophytes

Abstract Most wetland re-vegetation projects involve seedling transplantation. Sediment type and population density are of primary importance because they determine the fate of those seedlings. In order to ensure successful re-vegetation, an investigation was undertaken into the effect of three sediment types (sand, clay and their 50:50, v/v mixture), three densities (3, 9, 15 initial plants per tray) and their interaction on the growth of two common submerged macrophytes, Myriophyllum spicatum and Potamogeton crispus . Clay sediment resulted in a faster plant growth, including height, stem diameter and individual biomass than sand sediment for both species at low density. On clay, higher density induced faster growth in height for both species at first, and then slower growth at a later stage. In terms of root growth, M. spicatum and P. crispus had different responses to sediment type. On sand, M. spicatum allocated more biomass to roots while P. crispus allocated less, which resulted in a different root: leaf mass ratio. Density results showed different regulation patterns on individual biomass and shoot number, which were important in population establishment, on different sediment types for both species. On sand, medium density had the smallest individual biomass, while on clay, biomass increased with the decrease of density. On sand, little variation of shooter number showed among densities, while on clay, low density increased shoot number. All these results suggested that density had a feedback regulation on the effect of environmental resources, and combined consideration of these two factors is absolutely necessary before seedling transplantation.

Potential use of mangroves as constructed wetland for municipal sewage treatment in Futian, Shenzhen, China

A pilot-scale mangrove wetland was constructed in Futian, Shenzhen for municipal sewage treatment. Three identical belts (length: 33 m, width: 3 m, depth: 0.5 m) were filled with stone (bottom), gravel and mangrove sand (surface). Seedlings of two native mangrove species ( Kandelia candel, Aegiceras corniculatum) and one exotic species ( Sonneratia caseolaris) were transplanted to the belts with one species for each belt. The hydraulic loading was 5 m 3 d −1 and hydraulic retention time 3 d. High levels of removal of COD, BOD 5, TN, TP and NH 3–N were obtained. The treatment efficiency of S. caseolaris and A. corniculatum was higher than that of K. candel. Faster plant growth was obtained for S. caseolaris. The substrate in the S. caseolaris belt also showed higher enzyme activities including dehydrogenase, cellulase, phosphatase, urease and β-glucosidase. The removal rates of organic matter and nutrients were positively correlated with plant growth. The results indicated that mangroves could be used in a constructed wetland for municipal sewage treatment, providing post-treatment to remove coliforms was also included.

Tree establishment along an ENSO experimental gradient in the Atacama desert

AbstractQuestions: (1) What are the roles of regional climate and plant growth rate for seedling establishment during ENSO rainy pulses along the western coast of South America? (2) What is the water threshold for tree seedling establishment in these arid ecosystems?Location: Atacama Desert, western South America: Piura (5°10’ S, 80°37’ W), Mejia (17°00’ S, 71°59’ W), Fray Jorge (30°41'S,71°37'W).Methods: We experimentally simulated a gradient of ENSO rainfall in three locations encompassing the total extent of the Atacama Desert to test the relative importance of regional climate for seedling establishment during rainy pulses. We also carried out a common garden experiment to test the role of potential interspecific differences in growth rate among two Prosopis tree species.Results: Water threshold for seedling survival increased towards the south with less than 27 mm required in Piura, 100 mm in Mejia and 450 mm in Fray Jorge. We found that seedling survival and growth rate (shoots and roots) were much higher in Piura than in the other two sites for both Prosopis species.Conclusions: Our results indicate that tree establishment during rainy pulses is more likely to be successful in regions where rain falls during warm months and stimulates fast plant growth, and where loose soil texture facilitates deep root growth and therefore access to more stable water sources.

Tree establishment along an ENSO experimental gradient in the Atacama desert

Questions: (1) What are the roles of regional climate and plant growth rate for seedling establishment during ENSO rainy pulses along the western coast of South America? (2) What is the water threshold for tree seedling establishment in these arid ecosystems? Location: Atacama Desert, western South America: Piura (5°10' S, 80°37' W), Mejia (17°00' S, 71°59' W), Fray Jorge (30°41' S, 71°37' W). Methods: We experimentally simulated a gradient of ENSO rainfall in three locations encompassing the total extent of the Atacama Desert to test the relative importance of regional climate for seedling establishment during rainy pulses. We also carried out a common garden experiment to test the role of potential interspecific differences in growth rate among two Prosopis tree species. Results: Water threshold for seedling survival increased towards the south with less than 27 mm required in Piura, 100 mm in Mejia and 450 mm in Fray Jorge. We found that seedling survival and growth rate (shoots and roots) were much higher in Piura than in the other two sites for both Prosopis species. Conclusions: Our results indicate that tree establishment during rainy pulses is more likely to be successful in regions where rain falls during warm months and stimulates fast plant growth, and where loose soil texture facilitates deep root growth and therefore access to more stable water sources.