Investigating the Effect of Intraspecific Competition on the Growth of Mung Beans

Investigating the effect of intraspecific competition on the growth of mung beans

Introduction

When plants reproduce, size is highly correlated with reproductive. The struggle for reproductive survival among plants is the struggle to grow in the face of competition from neighbours. So the question this experiment asks is how competition affects the growth of plants. A plant growing in a nutrient-abundant environment free from competition will exhibit maximum growth.

One way to address this question is to grow the organism alone in controlled environment and grow organisms in another controlled environment in the laboratory. Such laboratory experiments can manipulate population density as well as environmental factors such as nutrients and light.

In the experiment, density (ie. no. of organisms) will be varied. We will use mung beans, as the experimental units. In the experiment, plants will be grown in monospecific plots.

Growth and development of plants occurring in soil habitats may be determined by a combination of abiotic and biotic factors. Competition affects biomass production mung beans in soil. Increases in plant density may lead to an asymmetric frequency distribution of plants in which there are a few large individuals and numerous small plants or to a symmetrical competitive response in which all individuals have an equal decline in biomass production. In the case of asymmetric distribution, size variation among plants generally increases when there is competition for light because larger individuals may reduce light available to smaller individuals and thus suppress their growth. Smaller individuals might be lost due to high density-dependent mortality, because mung beans have relatively high light requirements.

Intraspecific competition is reported to reduce biomass production in mung bean plant in both field and laboratory investigations. Although much is known about the whole plant response to intraspecific competition, little is known about the mechanisms responsible for density dependent growth inhibition in soil.

Hypothesis

All species, including plants, are impacted by density. Plants, of course, cannot leave their habitat as animals can, so they tend to respond in different ways to density. As populations grow denser, they compete for resources such as food and space and are more prone to disease. Less dense populations are more susceptible to predation pressure.

It is hypothesized that as plants in small spaces compete for space, the plants compensate by reducing individual stem weight and frequency of bud formation as density increases. This would be intraspecific competition. A factor is density-dependent when it kills more of a population at higher densities and less at lower densities. The factor of competition between individual plants of the same species would be considered density dependent.

Therefore I predict that as the density increases the intraspecific competition for nutrient and light increases. This will result in plants being smaller and weaker in the pot containing high density (ie. more no. of mung beans)

Equipments and method

The experiment conducted to investigate the growth of mung beans is simple. Therefore we wouldn’t be using any complicated equipments for this experiment. The equipments required to measure the growth of the plant are:

Mung beans,

Ruler to measure height,

Graph paper to measure the surface area of the leaf,

Balance to weigh the dry mass of mung beans,

3 plastic pots with same surface area, weight and shape to grow the mung beans,

soil containing no harmful organisms or substances that doesn’t affect the growth of the mung beans,

light source for photosynthesis and growth of mung beans,

water as a source of nutrients for the mung beans,

straight stick to ensure the shoot grows upwards (e.g. pin, thin refill of a pen)

This experiment is best when conducted in a greenhouse as all the abiotic factors are controlled such as amount of light, CO2, Humidity, temperature, etc.

First the mung beans should be soaked in water for a day to allow germination. 3 pots are filled with equal amount of soil. Each pot is named A, B and C.

1 sprouted mung bean is sown in Pot A, 10 sprouted mung beans in Pot B and 25 in Pot C. Ensure that all the seeds are sown in the same level. They shouldn’t be sown too deep or very near the surface of the soil. These pots are then placed in a greenhouse. Ensure the pots are placed in same kind of place, so that the mung beans in the pots receive equal amount of CO2 and light. Water the plants equally on frequent days. When the shoots start to grow, use a straight stick to help the shoot grow in 1 direction After 3 weeks the plants are taken out of the soil and measured for differences.

This experiment is carried out twice to obtain an average measure to improve the quality of the statistical data.

Variables

Independent variable

The number of beans per pot is different. There is 1 bean in pot A. 10 beans in Pot B. and 25 beans in Pot C. this is made different to obtain a statistical data of differences between beans in each pot. This affects the dependent variable.

Dependent variable

This is the observed variable in an experiment whose changes are determined by the presence of one or more independent variables. In this case it is the percentage increase of biomass or growth.

Controlled variable

These are the variables that will be kept constant throughout the experiment to obtain a fair statistical data. In this experiment the constant variables are volume of soil, nutrients in soil, pH of the soil, microbes in soil, amount of light, temperature, amount of water, age of the beans, etc

However, some beans will be different to others due to its genetic variation. This cannot be known until it has grown a shoot. Therefore this variable cannot be controlled.

Observations & Measurements

The light