Krish Jayachandran

Growth response and phosphorus uptake by arbuscular mycorrhizae of wet prairie sawgrass

Sawgrass (Cladium jamaicenseCrantz) is one of the dominant species of South Florida’s wetland ecosystems. The objectives of this study were to investigate the mycorrhizal status of natural sawgrass in soils such as the Everglades organic peat, calcium carbonate marl, and low elevation pine rockland sandy soils and to determine the growth response and phosphorus uptake due to arbuscular mycorrhizal fungi (AMF) inoculation under different soil types. An initial survey revealed that AMF population near the root zone of sawgrass varied among the sites and soil types, ranging from 936 to 6214 spores per 50 g dry soil. The AMF colonization of sawgrass roots varied among sites and soil types, ranging from 0 to 41%. In a greenhouse pot experiment, AMF inoculation significantly ( P< 0.05) increased sawgrass growth (14%), shoot (52%) and root (66%) biomass, and P uptake (58%) compared to control plants in organic peat soil under saturated conditions. Receding soil water levels during dry season in the Everglades wetland is potentially conducive for the beneficial sawgrass–AMF association.

RESPONSES OF TWELVE TREE SPECIES COMMON IN EVERGLADES TREE ISLANDS TO SIMULATED HYDROLOGIC REGIMES

Twelve tree species common in Everglades tree islands were subjected to three hydrologic regimes under controlled conditions for 25 weeks and assessed for growth and physiological responses. Treatments representing high, low, and no flood were maintained in pools of water to mimic seasonal variation in water depths at different positions in tree islands. Soil inundation under the high flood treatment resulted in reduced tree growth (height, basal diameter, crown volume) that was more pronounced and occurred earlier in mesic forest species than in swamp forest species. Physiological responses differed less among species, although stomatal conductance was a better predictor of the effects of flood stress on growth than either relative water content or chlorophyll fluorescence (Fv/Fm). Some swamp species appeared to be better adapted to rising water levels than others; Annona glabra, Morella cerifera, and Salix caroliniana responded more positively to flooding, while Magnolia virginiana, Persea borbonia, Chrysobalanus icaco, and Ilex cassine were less flood-tolerant. The highest mortalities and lowest growth were observed in the five upland species: Bursera simaruba, Coccoloba diversifolia, Eugenia axillaris, Sideroxylon foetidissimum, and Simarouba glauca. Of these, Sideroxylon and Simarouba did not survive to the end of the study under the high flood treatment. The moist soil conditions simulated by the low flood treatment resulted in greater growth in all species compared to soil inundation under high flood, except for the most flood-tolerant (Annona, Morella, Salix). The arrangement of species according to their responses to experimental flooding roughly paralleled their spatial distribution in the tree islands. The gradient in species responses demonstrated in this experiment may help guide responsible water management and tree island restoration in the Everglades.

Effect of soil pH on growth, nutrient uptake, and mycorrhizal colonization in exotic invasive Lygodium microphyllum

Lygodium microphyllum is an invasive exotic plant species taking over many sites in freshwater and moist habitats in Florida. Managing it has been a significant challenge for land resource managers and researchers due to its extensive rapid invasion. To assess the effects of soil pH on growth, nutrient uptake, and mycorrhizal colonization in the roots of L. microphyllum, we conducted a 60-day greenhouse experiment by growing it in pots filled with pH-adjusted soils to a range from 4.5 to 8.0. L. microphyllum was able to survive and grow at all soil pH levels; however, final biomass, relative growth rate, photosynthesis, and specific leaf area were all greater in soil pH 5.5–6.5 compared to the other treatments. Correspondingly, nitrogen concentration was also related to these four plant parameters. Root colonization by mycorrhizal fungi was higher in soil pH 5.5–7.5 and lowest for plants growing in 4.5 or 8.0 and was correlated with plant growth parameters as well as elemental concentration in the leaves. Soil pH 8.0 was not strong enough for a pronounced growth decline, thus further increasing soil pH could provide a desired outcome and merit further investigation, although its potential negative impact on native flora (both plants and microorganisms) would need to be assessed.

Mycorrhizal symbiosis and Lygodium microphyllum invasion in south Florida - a biogeographic comparison.

Lygodium microphyllum (Old World Climbing Fern) is one of the most problematic weeds in south Florida, invading numerous habitats from mangroves to pine flatwoods natural ecosystems. Much of the research efforts on L. microphyllum has been focused on reproductive potential, spore release, growth under different environmental conditions, belowground rhizome dormancy and survival strategies that describes its invasiveness. However, the role of an important mutualistic association with arbuscular mycorrhizal fungi (AMF) in the competitive ability and successful invasion of L. microphyllum by enhancing nutrient uptake has not been previously considered. Analysis of field root and soil samples from the ferns introduced and native range as well as a 7-week growth chamber experiment were done to determine the level of mycorrhizal colonization in the roots of L. microphyllum and the dependency on mycorrhizal fungi for growth and phosphorus (P) uptake. The field root samples showed that L. microphyllum was heavily colonized by AMF in relatively drier conditions, which are commonly found on some Florida sites compared to more common wetter sites where the fern is found in its native Australia. The results from the growth chamber experiment showed that the mycorrhizal treatment plants had significantly higher relative growth rate and biomass compared to the non-mycorrhizal plants. Similarly, L. microphyllum was highly dependent on the mycorrhizal fungi for growth and P uptake. Our results suggest that AMF play a significant role in vegetative reproduction and likely enhance the invasiveness of L. microphyllum in south Florida natural areas.

Microbial Ecology and Everglades Restoration

Much of the activity proposed for Everglades restoration is associated with processes either controlled by or impacting microbial activities. The authors summarize some recent studies related to restoration objectives conducted in a range of Everglades environments, including marsh and tree island soils, and periphyton assemblages. These studies include research related to the development of restoration performance measures based on nutrient status, analysis of controls on organic matter decomposition that may have lead to the development of soil microtopography responsible for water flow paths, microbial drivers of methane production, and analysis of the architecture of periphyton mats and their potential use in nutrient removal treatment strategies. The authors highlight the complexity inherent in microbial control of biogeochemistry, as well as the multitude of approaches that are needed to explain these interactions. Compared to larger ecosystem attributes such as vegetation community structure, the structure and function of microbial communities have remained elusive, and significantly more research into this area is essential to ensure that restoration goals are accomplished.

Buckwheat as a Cover Crop in Florida: Mycorrhizal Status and Soil Analysis

Buckwheat (Fagopyrum esculentum Moench) is an excellent choice as a cover crop. Buckwheat grows quickly and is utilized as a cover crop for weed suppression, a nectar source for native pollinators, and for soil nutrient enrichment, primarily phosphorus. Even though buckwheat is not commonly grown in Florida’s subtropical zone, it has the potential to be grown as a cover crop supporting sustainable agroecosystem. The purpose of this research was to analyze the suitability of buckwheat as a cover crop in Florida in conjunction with a comprehensive assessment of its response to arbuscular mycorrhizal fungi inoculation, soil types, and its effect on soil nutrient enrichment. Buckwheat was planted at the Florida International University organic garden (Miami, FL, USA) in early November and harvested in mid-December. After incorporation of buckwheat residues, soil analyses indicated the ability of buckwheat to enrich soil with major nutrients, in particular, phosphorus and nitrogen. Correlation analysis on aboveground buckwheat biomass and soil characteristics showed that high soil pH was the major limiting factor that affected buckwheat growth. Results also showed that buckwheat forms symbiosis with arbuscular mycorrhizal fungi; buckwheat root colonization ranges from low to medium. Symbiosis with arbuscular mycorrhizal fungi increased inorganic phosphorus uptake and overall buckwheat growth.

Biodegradation of polyether algal toxins--isolation of potential marine bacteria.

Marine algal toxins such as brevetoxins, okadaic acid, yessotoxin, and ciguatoxin are polyether compounds. The fate of polyether toxins in the aqueous phase, particularly bacterial biotransformation of the toxins, is poorly understood. An inexpensive and easily available polyether structural analog salinomycin was used for enrichment and isolation of potential polyether toxin degrading aquatic marine bacteria from Florida bay area, and from red tide endemic sites in the South Florida Gulf coast. Bacterial growth on salinomycin was observed in most of the enrichment cultures from both regions with colony forming units ranging from 0 to 6 × 107 per mL. The salinomycin biodegradation efficiency of bacterial isolates determined using LC-MS ranged from 22% to 94%. Selected bacterial isolates were grown in media with brevetoxin as the sole carbon source to screen for brevetoxin biodegradation capability using ELISA. Out of the two efficient salinomycin biodegrading isolates MB-2 and MB-4, maximum brevetoxin biodegradation efficiency of 45% was observed with MB-4, while MB-2 was unable to biodegrade brevetoxin. Based on 16S rRNA sequence similarity MB-4 was found have a match with Chromohalobacter sp.

Arbuscular Mycorrhizae and Their Role in Plant Restoration in Native Ecosystems

There is high plant biodiversity in southern Florida, due to the floristic mixing of warm temperate Southeastern North America and tropical Caribbean. Arbuscular mycorrhizal (AM) fungi were found in the roots of native plants in the families Anacardiaceae, Arecaceae (Palmae), Cactaceae, Convolvulaceae, Cycadaceae, Euphorbiaceae, Fabaceae, Lauraceae, Rubiaceae, Simarubaceae and Smilacaeae that grow in the coastal maritime and inland hammocks of southern Florida. Seedlings of the following genera: Amorpha, Coccothrinax, Gymnanthes, Hamelia, Jacquemontia, Licaria, Nectandra, Opuntia, Picramnia, Psychotria, Rhus, Sabal, Serenoa and Zamia inoculated with AM fungi showed enhancement of growth and phosphorus uptake on local sandy, nutrient poor soils. Most native species were depend on AM fungi under natural conditions of poor or no soils, phosphorus limitations and often water stress. Restoration of endangered species of Amorpha (Fabaceae), Jacquemontia (Convolvulaceae), Opuntia (Cactaceae) and Pseudophoenix (Arecaceae) was considered using AM fungi. The symbiotic relationship between AM fungi and native plants is important in the low P ecosystem and also useful for restoration of native plants.

Erratum to: Isolation and molecular characterization of the fungal endophytic microbiome from conventionally and organically grown avocado trees in South Florida

Fungal endophytes are the most ubiquitous and highly diverse microorganisms that inhabit the interior of healthy plants. They are important in plant ecology and offer untapped potential to improve plant health and productivity in agroecosystems. The endophytic assemblage of avocado is poorly understood; therefore, surveys of fungal endophytes of Persea americana Mill. (Avocado) in South Florida organic and conventional orchards were conducted. A total of 17 endophytic fungal species were recovered from healthy avocado terminal branches. Endophytic fungal species were identified by rDNA sequencing of the internal transcribed spacer (ITS) region, using UNITE Species Hypotheses to reliably assign a taxon name, and determined as belonging to the genera Alternaria, Cladosporium, Colletotrichum, Corynespora, Diaporthe, Lasiodiplodia, Neofusicoccum, Neopestalotiopsis, Phyllosticta, and Strelitziana. Endophyte community assemblage differed between organic and conventional agroecosystems. This is the first report of Alternaria eichhorniae, Cladosporium tenuissimum, Corynespora cassiicola, Colletotrichum alatae, Diaporthe fraxini-angustifoliae, Lasiodiplodia gonubiensis, Neofusicoccum algeriense, Neofusicoccum andinum, Neopestalotiopsis foedans, Phyllosticta capitalensis, and Strelitziana africana as endophytes of avocado. Evaluation using pathogenicity tests on avocado leaves and terminal branches showed that endophytic fungal isolates did not cause disease symptoms.

Recirculating Aquaculture Systems (RAS) and Aquaponics for Urban Food Production, with a Pictorial Guide to Aquaponics

As wild-caught fish landings plateau and the global population grows, aquaculture has emerged as the fastest-growing agricultural sector. In the context of urbanization, we present the challenges and opportunities surrounding fish farming in its various forms. Intensive, highly controlled recirculating aquaculture systems (RAS) treat and recycle fish effluent to maximize fish yields while conserving water. As a subset of RAS, aquaponic systems further enhance water use efficiency and reduce waste by including a hydroponic component that produces marketable plant crops. We discuss details of aquaponic system design and operation and provide a pictorial guide to the aquaponic system at the Rutgers EcoComplex.