Wetlands the growth andcontributed to the survival

Wetlands are terrestrial ecosystems characterized by high and fluctuating water tables. Thespatial and temporal differences in the degree to which wetland soils are waterlogged create avery dynamic soil environment with, on average, lower oxygen concentrations thanunsaturated soils. Wetland soils are characterized by gradients in redox conditions from totallyoxidized to extremely reduced. These conditions require special adaptations for the plant andmicrobial species in the wetland. Agusan Marsh is one of the most ecologically significantwetlands in the Philippines. Found in the heart of Mindanao's Agusan Basin, this vast expanseof marsh covers an area roughly the size of Metro Manila. It contains nearly 15% of the nation'sfresh water resources in the form of swamp forests. Metroxylon sagu Rottb. (sago palms)commonly abundant in the Agusan Marsh of Mindanao exhibit interestingly luxuriant growth.These plants do not only adapt to the strong fluctuating water tables in the wetlands andshortage of oxygen in the root zone, but also to extended periods of dry conditions during low-water phases. Sago palms and other plants located in Agusan Marsh were closely associatedwith various bacteria, fungi and insects. Microbial communities isolated from the Agusan Marshinclude potential plant growth-promoting rhizobacteria (PGPR) and fungi. PGPR isolated fromthe rhizosphere of sago plams were initially screened and observed to have growth-promotingproperties. The ability of these sago palms to adapt to acidic peat soil and oxygen-deficientenvironments in the marsh may be attributed to the presence in the rhizosphere of thesebeneficial bacteria. The growth responses of acclimatized sago palm suckers cultivated ingarden soil inoculated singularly with three PGPR strains were enhanced. The isolates werefound to colonize the root-soil environment in the transplanted acclimatized sago palm suckers.This soil inoculation study demonstrated that the isolates promoted the growth andcontributed to the survival of the acclimatized sago suckers. The suckers inoculated with theseisolates exhibited high rate of girth increase, promoted leaf emergence and improved thehealth status of the suckers. The growth-promoting properties were observed as evidenced byan increase in radicle length in corn varieties NK 5447 Bt and NK 5447 and increase in shootlength in tomato varieties Pope and Diamante. Antifungal properties against Penicillium sp. andCurvularia sp. were also reported in the same tomato varieties. Polyphasic approach identifiedthe PGPR as Bacillus subtilis, Agrobacterium tumefaciens and Pseudomonas veronii. Theserhizobacterial species produced exopolysaccharides and fixed nitrogen, enabling them to beefficient plant growth-promoting rhizobacteria in the rhizosphere of sago plams. These bacteriaare important in wetlands because they are involved in the nutrient cycling by using alternativeelectron acceptors such as nitrate, iron, manganese, sulphate and carbon dioxide. Thesemicrobial communities also play role in maintaining the balance of the ecosystem in wetlands.Meanwhile, the fungi isolated from rotten roots of sago plams in Agusan marsh help in thedecomposition of dead plant materials and nutrient cycling. The insects associated with sagopalms belong to the genus Rhynchophorus. Without these insects to help break down anddispose of wastes, dead animals and plants would accumulate in the marsh. Palm weevils arescavengers, feeding on dead animals and fallen trees, thereby recycling nutrients back into themarsh. Insects such as these palm weevils are underappreciated for their role in the food web.They are the sole food source for many amphibians, reptiles, birds, mammals and even humans.People around Agusan marsh eat the palm weevils (batud) from sago palms which is now afavorite delicacy. With the “batud” considered such a delicacy, it is suggested that it might bepossible to combine increased production with more efficient recycling of dead and diseasedpalms and as part of reduced-pesticide integrated pest management programs and diseasecontrol on coconut and other palms in the marsh. Plant–microbe interactions therefore add tothe complexity of the functioning of the wetland ecosystem.

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