The Effect of Uv-C Light on the Growth and Development of Brassica Rapa Seedlings

Topics: Ultraviolet, Sunlight, Sun Pages: 5 (1859 words) Published: April 13, 2011
ABSTRACT: By exposing Brassica rapa seedlings to UV-C light, the effect of the growth and development of Brassica rapa seedlings was tested. The experimental group of Brassica rapa seedlings was exposed to 254 nm UV-C light for thirty seconds after one week of growth. Throughout the duration of one month, the height, number of leaves and stem diameter were measured sporadically. After one month, the biomass of the seedlings was recorded. A starch analysis test was also performed. According to the results, the stem diameter of the experimental group exposed to the ultraviolet light was significantly smaller than that of the control group exposed to full spectrum light. The number of leaves, height, biomass and the starch production were unaffected by the ultraviolet light exposure.

INTRODUCTION: In this experiment, Brassica rapa, Wisconsin Fast Plants, were grown and examined during their full lifecycle of twenty-eight days. The growth rate is important to the fitness in evolution of competitive interactions for the Brassica rapa plant. Brassica rapa are members of the crucifer family plants, which is close to cabbage and broccoli (4). These plants are fast cycling plants, so once they are planted, they begin to germinate and grow two days later. By the fourteenth day, they already have yellow flowers. After a month or so they begin to wilt and die, but they still have seed embryos that are waiting to start a new cycle (4).

Light is necessary for plant growth because they use the energy received from light to synthesize its own food, glucose, in a process called photosynthesis. Sunlight supplies all different wavelengths, which are broken up into red, orange, yellow, green, blue, indigo and violet. Plants will absorb a color from the sunlight but transmit or reflect another (2). Plants use sunlight in photosynthesis and are therefore exposed to ultraviolet (UV) radiation that is present in sunlight. UV radiation is divided into three classes: UV-C, UV-B, and UV-A. Like all living organisms, plants respond to UV radiation, both UV-A (320-390 nm) and UV-B (280-320 nm) present in sunlight, and wavelengths below 280 nm, UV-C (3). All types of UV radiation are known to damage several plant processes. Damage by UV radiation is classified into two categories: damage to DNA and damage to physiological processes. Exposure to UV light can cause damage to DNA, which can cause heritable mutations in a plant’s DNA. In order prevent this, damage to DNA must be repaired before DNA replication by the following mechanisms: photoreactivation, excision repair, or recombinational repair. Damage to plants’ physiological processes could include tissue damage and photosynthetic damage as well (3). Through this experiment, we will test to see how Brassica rapa will grow and develop under UV-C light exposure versus the controls that are exposed to full spectrum light. It was hypothesized that the Brassica rapa plants exposed to UV-C light will be underdeveloped, expressed by a lower: stem length, stem diameter, biomass, number of leaves and starch production. MATERIALS & METHODS: In order to begin the experiment, we obtained two 16-cell quads that would be used to grow our plants. Diamond-shaped wicks were threaded through a hole in each cell, allowing the wick to go half way in and half way out of the cell. Labels were placed on each cell: 1-16 Control and 1-16 UV. Each quad cell was filled approximately 2/3 full with potting soil. Two fertilizer pellets were placed in each cell and covered with ¼” layer of additional planting medium. To ensure that each cell would have at least one plant, two seeds were added to each cell in a depression. The seeds were then covered with ¼” layer of additional potting soil and each cell was watered with a 1 ml pipette until the wicks dripped. A plastic container was filled with water and a felt cloth was placed over the lid of the container. The felt cloth was soaked with water and the quads were...
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