K. G. Mukerji

Improved Tolerance of Acacia nilotica to Salt Stress by Arbuscular Mycorrhiza, Glomus fasciculatum may be Partly Related to Elevated K/Na Ratios in Root and Shoot Tissues

A pot experiment was conducted to examine the effect of arbuscular mycorrhizal fungus, Glomus fasciculatum, and salinity on the growth of Acacia nilotica. Plants were grown in soil under different salinity levels (1.2, 4.0, 6.5, and 9.5xa0dS m−1). In saline soil, mycorrhizal colonization was higher at 1.2, 4.0, and 6.5xa0dS m−1 salinity levels in AM-inoculated plants, which decreased as salinity levels further increased (9.5xa0dS m−1). Mycorrhizal plants maintained greater root and shoot biomass at all salinity levels compared to nonmycorrhizal plants. AM-inoculated plants had higher P, Zn, and Cu concentrations than uninoculated plants. In mycorrhizal plants, nutrient concentrations decreased with the increasing levels of salinity, but were higher than those of the nonmycorrhizal plants. Mycorrhizal plants had greater Na concentration at low salinity levels (1.2, 4.0xa0dS m−1), which lowered as salinity levels increased (6.5, 9.5xa0dS m−1), whereas Na concentration increased in control plants. Mycorrhizal plants accumulated a higher concentration of K at all salinity levels. Unlike Na, the uptake of K increased in shoot tissues of mycorrhizal plants with the increasing levels of salinity. Our results indicate that mycorrhizal fungus alleviates deleterious effects of saline soils on plant growth that could be primarily related to improved P nutrition. The improved K/Na ratios in root and shoot tissues of mycorrhizal plants may help in protecting disruption of K-mediated enzymatic processes under salt stress conditions.

Mycorrhizal inoculant alleviates salt stress in Sesbania aegyptiaca and Sesbania grandiflora under field conditions: evidence for reduced sodium and improved magnesium uptake

A field experiment was conducted to examine the effect of the arbuscular mycorrhizal fungus Glomus macrocarpum and salinity on growth of Sesbania aegyptiaca and S. grandiflora. In the salt-stressed soil, mycorrhizal root colonisation and sporulation was significantly higher in AM-inoculated than in uninoculated plants. Mycorrhizal seedlings had significantly higher root and shoot dry biomass production than non-mycorrhizal seedlings grown in saline soil. The content of chlorophyll was greater in the leaves of mycorrhiza-inoculated as compared to uninoculated seedlings. The number of nodules was significantly higher in mycorrhizal than non-mycorrhizal plants. Mycorrhizal seedling tissue had significantly increased concentrations of P, N and Mg but lower Na concentration than non-mycorrhizal seedlings. Under salinity stress conditions both Sesbania sp. showed a high degree of dependence on mycorrhizae, increasing with the age of the plants. The reduction in Na uptake together with a concomitant increase in P, N and Mg absorption and high chlorophyll content in mycorrhizal plants may be important salt-alleviating mechanisms for plants growing in saline soil.

Influence of arbuscular mycorrhizal fungi and salinity on growth, biomass, and mineral nutrition of Acacia auriculiformis

The effect of salinity on the efficacy of two arbuscular mycorrhizal fungi, Glomus fasciculatum and G. macrocarpum, alone and in combination was investigated on growth, development and nutrition of Acacia auriculiformis. Plants were grown under different salinity levels imposed by 0.3, 0.5 and 1.0xa0S m-1 solutions of 1xa0M NaCl. Both mycorrhizal fungi protected the host plant against the detrimental effect of salinity. The extent of AM response on growth as well as root colonization varied with fungal species, and with the level of salinity. Maximum root colonization and spore production was observed with combined inoculation, which resulted in greater plant growth at all salinity levels. AM fungal inoculated plants showed significantly higher root and shoot weights. Greater nutrient acquisition, changes in root morphology, and electrical conductivity of soil in response to AM colonization was observed, and may be possible mechanisms to protect plants from salt stress.

Glomus macrocarpum: a potential bioinoculant to improve essential oil quality and concentration in Dill (Anethum graveolens L.) and Carum (Trachyspermum ammi (Linn.) Sprague)

The effects of application of two arbuscular mycorrhizal (AM) fungi Glomus macrocarpum and G. fasciculatum on shoot biomass and concentration of essential oil in Anethum graveolens L. and Trachyspermum ammi (Linn.) Sprague fruits were evaluated. Results revealed significant variation in effectiveness of the two AM fungal species. AM fungal inoculation in general improved the growth of the plants. On mycorrhization, the concentration of essential oil increased up to 90% in dill and 72% in carum over their respective controls. Glomus macrocarpum was more effective than G. fasciculatum in enhancing the oil concentration. The constituents of the essential oils were characterized by gas liquid chromatography. The levels of limonene and carvone were enhanced in essential oil obtained from G. macrocarpum-inoculated dill plants, while G. fasciculatum inoculation resulted in a higher level of thymol in carum.

Vesicular arbuscular mycorrhiza — an overview

Living organisms in the biosphere exhibit a number of interactions which either alter their environment and/or the size and composition of each other’s populations. Of these, perhaps the most striking relationship is ‘symbiosis’ in which the partners live in a state of physical and physiological equilibrium and derive benifit from each other. There exist a number of plant-fungus relationships which are beneficial to both. They are called mycorrhiza. These are of various types but this chapter will give emphasis on the Endomycorrhiza also referred to as Vesicular-Arbuscular Mycorrhiza (VAM) or Arbuscular Mycorrhiza (AM). Vesicular Arbuscular Mycorrhiza (VAM) is one such association where fungal members of order Glomales colonize roots of higher plants. The fungal symbiont gets shelter and food from the plant which in turn aquires an array of benefits ranging from better uptake of phosphorus and relatively immobile micronurients like zinc and copper, increase in Nitrogen fixing capacity of leguminous plant species, salinity and drought tolerance, maintainence of water balance, increased rate of photosynthesis to overall increase in plant growth and development. Mycorrhizal plants show higher tolerance to high soil temperatures and various soil and root borne pathogens. In Eutrophic soil these plants can take up nitrogen in the form of ammonia. Seedlings which are colonized by these fungi perform better during transplantation. The mycorrhizal plants are also more tolerant towards heavy metal toxicity. A general lack of host-fungus specificity is evident by their widespread geographical distribution and also by the fact that almost eighty percent of the plant species show such association. A lot of work done in the past few decades has enabled these fungi to emerge as a potential biofertilizer; a cheap and environment friendly alternative to expensive, petroleum based chemical fertilizers. This aspect especially gains significance for a developing country like India where judicious and large scale utilization of this technology can prove very useful for getting maximum and long term gains in various wasteland reclamation, reforestation and afforestation programmes apart from giving a much needed thurst in the production of important agricultural crops on which the Economy of the country is dependent.

Preinoculation with Arbuscular Mycorrhizae Helps Acacia auriculiformis Grow in Degraded Indian Wasteland Soil

Abstract The effect of inoculation of two arbuscular mycorrhizal fungi, Glomus fasciculatum, and G. macrocarpum, alone and in combination, on establishment and growth of Acacia auriculiformis in a wasteland soil was studied under nursery and field conditions. Under nursery conditions, mycorrhiza-colonized seedlings showed significantly higher root shoot dry weights and higher concentrations of phosphorus (P), potassium (K), zinc (Zn), copper (Cu), iron (Fe), and sodium (Na) in shoots of mycorrhizal than nonmycorrhizal seedlings. However, concentration of calcium (Ca) was unchanged. Acacia auriculiformis exhibited a maximal mycorrhizal dependency of 79.6% on dual inoculation. Mycorrhizal dependency differed with AM fungal isolates and age of the plant. Under field conditions, AM colonization of A. auriculiformis enhanced tree survival rates (85%) after transplantation. Arbuscular mycorrhiza-colonized plants showed significant increase in height, biomass production, and girth as compared to nonmycorrhizal plants. In general, all growth parameters were higher on dual inoculation of G. fasciculatum and G. macrocarpum as compared to uninoculated plants under both nursery and field conditions.

VA Mycorrhizal Techniques / VAM Technology in Establishment of Plants under Salinity Stress Conditions

This chapter give a brief account about salt stress and its effect on plant growth, nutrition and on distribution, type and number of VAM fungi. VAM help in establishment of plants under salinity stress. Techniques to assess soil and plant activity has also been given.

Soil Factors in Relation to Distribution and Occurrence of Vesicular Arbuscular Mycorrhiza

The role of vesicular-arbuscular mycorrhizal fungi in yie,u augmentation of crop is well established yet little is understood about their growth, biology and ecology. These fungi form a symbiotic relationship with plant roots, and the fungal symbiont becomes a major interface or connection between soil and plants, therefore studies on mycorrhizal systems need to consider soil as well as plants and fungi. Soil proporties can affect spore germination, colonization of host roots and ability of the VAM fungi to influence the growth and physiology of the host plant. A high degree of edaphic specificity in indigenous asemblages of VAM fungi from contiguous soil has been observed. Soil physico-chemical characteristics viz. soil moisture, soil tempterature, soil pH, soil texture, nutrient levels alter the occurrence, distribution, and effectiveness of VA mycorrhizae.

Vesicular Arbuscular Mycorrhizae in Increasing the Yield of Aromatic Plants

The mycorrhizae represent one of nature’s best gifts to mankind in augmenting yield increase in plants. The increase in effective nutrient absorbing surface provided by vesicular arbuscular mycorrhizal (VAM) fungi is primarily responsible for the increase in uptake of soil nutrients by mycorrhizal plants. Because mycorrhizal fungi increase the efficiency of fertilizer use, they are referred to as ‘biofertilizers’ and can be substituted for substantial amounts of some fertilizers (Bansal and Mukerji, 1994).

Vesicular Arbuscular Mycorrhizal Fungi: Biofertilizer for the Future

Rapid desertification and soil erosion is a problem in the tropics due to adverse soil and climatic conditions. Marginal lands may also become barren due to deforestation. To prevent this degradation, marginal lands have to be afforested by overcoming the difficulties due to soil infertility. Sustainable agriculture and forestry have therefore taken centre stage among researchers, the public and policy makers Afforestation or revegetation of these barren lands through vesicular arbuscular (VA) mycorrhizal technology is an immediate necessity. The overall goal of forestry research is focused on increasing food, fibre, forage, fuel wood, fertiliser (root nodule) and timber production.