Role and influence of soil microbial communities on plant invasion

It is known that plant invasions are of major concern as they result in loss of biodiversity and alterations in ecosystem processes and functions. Although numerous mechanisms have been postulated to find out the reasons behind plant invasiveness, the actual and precise mechanism is still obscure. Soil microbes are considered as one of the important determinants of plant growth and establishment. Plant invasion leads to changes in the composition and structure of soil microorganisms. Most of the earlier studies have focused on the aboveground mechanisms of plant invasion. Recently the belowground mechanisms for plant invasion are being investigated. In this review, we focus on the various hypotheses related to soil microbes in either enhancing or suppressing plant invasions. The interactions between soil microbes with native and non-native plant species, the role of the plant-soil feedback system in the invasion and its impact, the function of mycorrhizal and bacterial symbiosis in plant species invasion and the role of soil biota and changes brought about in soil nutrient cycling and soil enzymes due to plant invasion are also discussed

Vegetative anatomy and mycorrhizal morphology of Schoenorchis nivea (Lindl.) Schltr., (Orchidaceae) and their adaptive significance

The anatomical description of the vegetative parts (leaf, leaf sheath, stem and root) and mycorrhizal morphology of Schoenorchis nivea (Lindl.) Schltr., belonging to the subfamily Epidendroideae of Orchidaceae was investigated. Leaves were amphistomatic covered by 10-12 µm thick cuticle, stomata paracytic with small and irregular substomatal chambers. Mesophyll homogenous, composed of thin-walled chlorenchymatous cells. Banded water-storage cells abundant in the mesophyll and the largest vascular bundle occurred at the centre of the leaf. The leaf sheath has both adaxial and abaxial epidermis covered with cuticle, homogenous mesophyll, water-storage cells, raphides and vascular bundles. The stem is surrounded by a uniseriate epidermis, cortex consisting of thick-walled fibers and collateral vascular bundles scattered in the ground tissue. Cortical proliferation was evident in S. nivea stem. Root hairs present in root regions were in contact with the substratum. Root hairs frequently branched at their tips. Root possess 2-3 layered velamen, ∩-thickened exodermal cells, O-thickened uniseriate endodermis, and cortex of thin-walled parenchymatous cells containing raphides and water-storage cells. Cover cells present. Xylem arches are 9-11, with vascular tissues embedded in sclerenchymatous cells. Pith composed of thick-walled sclerenchymatous cells with intercellular space. The stomatal characteristics in leaf, the size of water-storage cells and vascular bundles exhibited significant variation in different plant parts. Intact and degenerating pelotons of orchid mycorrhizal fungi were observed in the root cortical cells. The observations of the present study clearly indicate that S. nivea possesses several anatomical adaptations to thrive in epiphytic habitats

Vegetative anatomy of Tabernaemontana alternifolia L. (Apocynaceae) endemic to southern Western Ghats, India

The anatomical description of vegetative parts of Taberenaemontana alternifolia L. belonging to the family Apocynaceae was investigated in the present study. The leaves of T. alternifolia is hypostomatic with paracytic stomata, uniseriate epidermis made up of thin-walled parenchymatous cells covered by thin cuticle on both adaxial and abaxial surfaces. The hypodermis comprises of angular collenchyma cells. Mesophyll is dorsiventral containing silica bodies and vascular bundles are bicollateral. The petiole is flattened adaxially and arch-shaped abaxially with a uniseriate epidermis covered by a thin cuticle. The hypodermis is 7-8 layered angular collenchyma cells consisting of laticifers and parenchymatic, cortical layers consisting of silica bodies and thick-walled fibers and U-shaped bicollateral vascular bundles. Secondary growth in stems is characterized by the formation of periderm and thick-walled fibers in the vascular tissues. Bicollateral vascular bundles are covered by sclerenchymatous patches, parenchymatous cortex and pith consist of fibers, laticifers and silica bodies. The root possess unicellular root hairs, compactly arranged thin-walled uniseriate epidermis, 16-18 layered cortex containing silica bodies and fibers, indistinct endodermis, radially arranged vascular bundles and 14-16 arched xylem. Pitted water-storage cells are present in the conjunctive tissue. Lignin deposition was observed in the root stelar region and pith is absent

Asociación de hongos endofíticos en raíces de plantas medicinales exóticas cultivadas en Nilgiris, Western Ghats, India Peninsular: Asociación de hongos de raíz en plantas medicinales exóticas

Some soil beneficial microbes help in the establishment and growth of exotic medicinal plants. Therefore, we evaluated the presence and status of root endophyte [arbuscular mycorrhizal (AM) fungi and dark septate endophytic (DSE) fungi] association in ten exotic medicinal plant species cultivated in the Nilgiris of the Western Ghats. The AM fungi colonized all the examined plant species and eight plants had the co-occurrence of DSE fungi. The extent of fungal endophyte variables and root hair characteristics significantly differed among the medicinal plants. Six AM fungal spore morphotypes were identified in the soil samples. Thus, this study indicated the association of exotic medicinal plants with native AM and DSE fungi which could be exploited to promote growth and increase secondary metabolite production in these plant species. Algunos microbios beneficiosos para el suelo ayudan en el establecimiento y crecimiento de plantas medicinales exóticas. Por lo tanto, evaluamos la presencia y el estado de la asociación de endófitos de raíces [hongos micorrízicos arbusculares (AM) y hongos endofíticos septados oscuros (DSE)] en diez especies de plantas medicinales exóticas cultivadas en Nilgiris de los Ghats occidentales. El alcance de las variables endófitas de hongos y las características del pelo de la raíz difirieron significativamente entre las plantas medicinales. Se identificaron seis morfotipos de esporas de hongos AM en las muestras de suelo. Por lo tanto, este estudio indicó la asociación de plantas medicinales exóticas con hongos nativos AM y DSE que podrían explotarse para promover el crecimiento y aumentar la producción de metabolitos secundarios en estas especies de plantas

Asociación de hongos endofíticos en raíces de plantas medicinales exóticas cultivadas en Nilgiris (Western Ghats, India Peninsular)

Algunos microbios beneficiosos del suelo ayudan al establecimiento y crecimiento de plantas medicinales exóticas. Evaluamos la presencia y el estado de la asociación de endófitos de raíces [hongos micorrízicos arbusculares (AM) y hongos endofíticos septados oscuros (DSE)] en diez especies de plantas medicinales exóticas cultivadas en Nilgiris (Ghats Occidentales). Los hongos AM colonizaron todas las especies examinadas y ocho plantas tuvieron la co-ocurrencia de hongos DSE. El alcance de las variables de los hongos endofíticos y las características del pelo radicular difirieron significativamente entre las plantas. Se identificaron seis morfotipos de esporas de hongos AM. Por lo tanto, este estudio indicó la asociación de plantas medicinales exóticas con hongos nativos AM y DSE que podrían explotarse para promover el crecimiento y aumentar la producción de metabolitos secundarios en estas especies de plantas.Some soil beneficial microbes help in the establishment and growth of exotic medicinal plants. We evaluated the presence and status of root endophyte [arbuscular mycorrhizal (AM) fungi and dark septate endophytic (DSE) fungi] association in ten exotic medicinal plant species cultivated in the Nilgiris (Western Ghats). The AM fungi colonized all the examined plant species, and eight plants had the co-occurrence of DSE fungi. The extent of fungal endophyte variables and root hair characteristics significantly differed among the plants. Six AM fungal spore morphotypes were identified. Thus, this study indicated the association of exotic medicinal plants with native AM and DSE fungi which could be exploited to promote growth and increase secondary metabolite production in these plant species