Availability Of Mineral Nutrients Research Articles

Plant Response to Mycorrhizal Fungi: Host, Endophyte, and Soil Effects

AbstractInteractions and growth responses in soybean [Glycine max (L.) Merr.] and sorghum [Sorghum bicolor (L.) Moench] colonized by the vesicular‐arbuscular mycorrhizal (VAM) fungi [Glomus fasciculatum (Thaxt. sensu Gerd.) Gerd. and Trappe] or [Glomus mosseae (Nicol. & Gerd.) Gerd. and Trappe] as grown in three northern California soil types were investigated in a 2 by 2 by 3 factorial experiment. Growth and development of both symbiotic partners were significantly influenced by all three factors (host plant, endophyte, soil). Growth responses to VAM‐fungal colonization varied with soil type from −10 to 400%. Phosphorus concentrations increased significantly in all soybean and some sorghum plants relative to non‐VAM controls as a result of VAM‐fungal colonization. Shoot dry matter as percent of fresh weight increased significantly in only those VAM plants which had also experienced a significant growth enhancement. Root/shoot ratios of most VAM plants were lower than those of the controls. Changes in root/shoot ratios were inversely related to changes in dry weight. The results show that soil type, as well as the host‐endophyte combination, is a significant factor in modifying the VAM growth effect independently of mineral nutrient availability.

Effects of Nutrients and Light on Growth and Root Formation in Pisum sativum Cuttings

AbstractCuttings obtained from seedlings of Pisum sativum L. were rooted in water solution. Shoot growth continued after excision and shoot length increased considerably before roots emerged. Increase in dry weight was strongly dependent on light supply. Continued growth was dependent on supply of mineral nutrients to the rooting solution.Mineral nutrients had no or slight influence on the number of roots formed on cuttings from stock plants grown in fertilized soil, but the growth in length of the roots was dependent on the presence of calcium in the solution. Root formation was dependent on photosynthetic products formed after excision. No roots were formed on cuttings kept in the dark. The number of roots increased with increasing irradiance given to the leafy part of the cutting. At a low level of irradiance sucrose supply through the rooting medium increased the number of roots. Light given to the basal part of the cuttings had a strongly inhibitory effect on the number of roots formed. It is concluded that the carbohydrate level easily becomes a limiting factor for root formation in growing pea cuttings. Availability of mineral nutrients influences in the first place the growth of the shoots.

Effects of Fire on the Chemical Status of Herbaceous Communities of the Derbyshire Dales

It has previously been demonstrated that sporadic burning is an important influence in determining the nature of some types of limestone grassland in the Derbyshire Dales (Lloyd 1968). There are both short-term effects (seen in the transient abundance of annual and biennial species) and long-term effects (seen in changes in abundance of the dominant grasses and in control of scrub invasion). When a plant community is burned, in addition to the damage to plants and alterations to the physical environment, there are considerable changes in the chemical status of the community. There may be a substantial loss of nutrients in the smoke or in windblown ash and there may also be a release of readily soluble nutrients in the deposited ash. The significance of such chemical changes in herbaceous communities on limestone soils is assessed in this paper. Forest fires usually result in a clear increase in the availability of mineral nutrients (Ahlgren & Ahlgren 1960), but grassland fires are not reported to have so marked an effect, possibly because of the smaller standing crop (Daubenmire 1968). In Britain Allen (1964) and Allen, Evans & Grimshaw (1969) have investigated the chemical aspects of fire in Callunetum, an ericaceous community of acidic, peaty soils. The present study provides a contrast in that the grassland and tall herb communities examined all occur on soils containing free calcium carbonate. Changes in the nutrient status of the plant-soil system after fire have been studied by estimating losses in the smoke, deposition in the ash, retention of soluble nutrients in the soil and by monitoring the nutrient content of vegetation at intervals after a fire.

Isolation and Characterization of Rhizosphere Bacteria and their Effect on Germination of Rice Seeds and Growth of Seedlings

Rhizosphere bacteria were isolated from root zones from rice fields. These were cultured in laboratory conditions and investigated the effects on germination and growth of rice seedlings. They inhabit around the roots and live on root exude and benefit the plants by altering the solubility and availability of mineral nutrients and protecting the roots from invasion of pathogens by creating an antibiotic barrier around the root. It has been found that rhizosphere bacteria have no effect on germination of rice seeds. Both the rhizosphere bacteria and the Agrobacterium have been found to produce better growth of rice seedlings in pot cultures but later is less effective than the former. Rhizosphere bacteria are mixtures of many e.g. Actimomyces, Proteobacteria, Pseudomonas etc. but Agrobacterium sp is single. Key words: Rhizosphere, Bacteria, Symbiosis, Soil microflora, Non-leguminous plants. doi: 10.3329/jbs.v15i0.2206 J. bio-sci. 15: 77-82, 2007

Food Crisis Nears Critical Stages

3 AN IMMENSE EFFORT must soon be made by politicians, educators, scientists and religious leaders if humanity is to win the unequal race between over-population and food production. Work must begin immediately if the world is to avoid the catastrophe of too many people and not enough food, Dr. J. George Harrar of the Rockefeller Foundation in New York said in opening a symposium at the annual meeting of the National Academy of Sciences, Washington. D.C. Man has learned to control four basic factors in his effort to increase prodLiction of certain food plants throughout the world, Dr. Frank W. Parker of the Agency of International Development and Lewis B. Nelson of the Tennessee Valley Authority stated. These four factors are: the genetic characteristics that produce stronger and healthier plants, the availability of fertilizers and mineral nutrients to supply energy to plants, the protection of these plants against disease and insects, and the control and use of water. The extent to which man can meet his food needs in the next 10 to 20 years will depend upon his ability to continue to manipulate these factors, the scientists reported. By maneuvering the genes that determine how strong and fine a plant grows. man has created superb hybrids of the food-producing plants, Dr. Paul C. Mangelsdorf of the Botanical Museum of Harvard University said. Annual production of the principal U. S. food crop, corn, has doubled since 1930, from 26 to 52 bushels per acre. Since that time, however no progress has been made in producing new hybrids that are more successful. To get the maximum benefit from hybrid seeds, farmers use fertilizers that add mineral nutrients to the growing plants. In the decade between 1950 and 1960, for instance, the use of nitrogen fertilizer has more than doubled, and other fertilizer chemicals have been used in increasing amounts. However, the use of fertilizer has certain limits, Dr. Mangelsdorf reported. For instance, in the Corn Belt and Lake states, which produce 73% of U.S. corn, 87% of the corn acreage is already being fertilized at an average rate of 145 pounds per acre. Applying greater amounts than this gives farmers a small return on their investment, and larger applications can even decrease the plant yield in seasons of poor rainfall. The third factor increasingly under C. Bovailgni