Effects of Rhizobia in Plant Yield

Topics: Nitrogen, Root, Nitrogen fixation Pages: 5 (1656 words) Published: October 31, 2012
PRACTICAL 2: FACTORS AFFECTING PLANT YIELD: Fertilization and Rhizobium inoculation Abstract
The study was to investigate the effect of inoculating pea and maize seedlings with rhizobium bacteria in terms of growth and yield. The seeds were grown under four types of treatments: rhizobium only, fertilizer only, rhizobium and fertilizer and negative control (no rhizobium and no fertilizer). The seeds were grown in a growth room and monitored for a period of 4 weeks. The results yielded some expected results and were not so expected. Over all the effect of rhizobium was seen in some plants and in some the effect was not that great e.g. no nodules were seen in pea plants but in maize nodules were visible. Again the results showed that fertilizer and rhizobium enhance the plant roots, shoots and leaves differently. But the combination of the two treatments indicated better resulted than the treatments on they own. Introduction

The most important plant performance to agricultural systems is the amount of yield they able to produce. Plants do not normally produce a lot of their yield and this might be due to a lot of confounding variables: climate change, pest problems, soil texture etc. These variables can happen both in the rhizosphere and atmosphere of the plant. Thus farmers have developed different strategies and mechanism that help increase plant yield and also protect the plants seeds and yield for generations to come. This paper focuses more on the rhizosphere part of the plants. It is known that “rhizosphere microorganism can stimulate the growth of plants by mobilization of nutrient and production of phytoeffective metabolites, protecting the plants from pathogen, decomposing toxic substances, increase the stress tolerance and stabilize soil structures (Hoflich, 1994). According to Hoflich, 1994, several types of rhizobium species are associated with the functions mentioned above. Many rhizobium species are well known for their ability to fix nitrogen from the soil and after become established inside root nodules of legumes (Stancheva et al. 2006). They provide nitrogen to the plants which is a very important but yet scarce compound in plants. In return the plants give the bacteria compounds like carbohydrate and proteins which are important in rhizobium bacteria. Other studies have reported that rhizobium bacteria can cover about 90% of the nitrogen requirements of legumes from atmosphere (Hoflich, 1994). Inoculation with rhizobium bacteria has shown to enhance the growth of nodules in many plants including pea and maize (Hoflich, 1994). Thus a study was conduced to investigate the impact of rhizobium bacteria inoculation on the growth and development of the Zea mays (maize) and Pisum sativa (pea) plants. Materials and Methods

At the beginning of the experiment trays of pea and maize seedlings (2 trays each) which were 7 days old were provided and they were grown in coarse vermiculite. The experiment involved comparing the treatments between species or within species under different growing regimes. The standard growing conditions in the growth room are ~27°C daytime/~19°C night, with a 16-h photoperiod. Light intensity was required to be measured and this can be done with a light meter. Procedures

Fertization and Rhizobium inoculation
Part 1:
Rhizobium species are bacteria that fix nitrogen from the soil. Farmers spray an amount of solution on the soil during planting of these bacteria. What happens is that the bacteria are taken by the roots of certain plant species and initiate the growth of nodules just below the soil surface. In the cells surface they than enter into a symbiotic nitrogen fixing relationship with the plant. It is said that nodules do not respond only to the bacterium but also respond to the often limited availability of certain mineral nutrients in an environment. This can be due to the mineral being absent from the soil or to constraints on the...

References: Hoflich, G., Wiehe, W and Kuhn, G. (1994). Plant growth stimulation by inoculation with symbiotic and associate rhizosphere microorganism. Review. 50, 897 – 905.
Stancheva, I., Geneva, M., Zehirov, G., Tsvetkova, G., Hristozkova, M and Georgiev, G. (2006). Effects of combined inoculation of pea plants with arbuscular mycorrhizal fungi and rhizobium on nodule formation and nitrogen fixing activity. General and Plant Physiology. 61 – 66.
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