What effect does the brightness of light have on the growth rate of a Coursework

What effect does the brightness of light have on the growth rate of a plant - Coursework Example Any change in the growth of plants will thus affect the ecosystem, and thus is important to be studied. In this experiment, pea plants were used to determine whether sunlight has an effect on plant growth. A group of growing seedlings were exposed to the sun, while another set was placed away from light. The heights of the plants were measured repeatedly for 7 days after the seed germination. Results are shown below. Figure 1: Scatter plot of the average values from Table 1. Standard deviations are indicated as error bars. It can be seen that plants L1-L5 were generally taller than D1-D5. As well, it can be noted that the rate at which the plants grow from day 7 to day 14 are faster in well-lit plants than in non-lit plants, as the slope of the trend line for the former is steeper than that of the latter. Conclusion After the experiment, it was observed that well-lit plants grow longer than the non-lit plants. Sunlight is thus necessary in the growth of plants. Theory Photosynthesis Sunlight, through the photons it bears, drives photosynthesis, the food-making process of plants. Without it, plants do not have a source of nutrition needed to power even the most basic processes such as growth (Campbell and Reece, 2002). Photosynthesis is a collection of reactions that results in the reduction of carbon dioxide (CO2) to carbohydrate and the production of oxygen gas (O2) from water (H2O). Pigment molecules such as chlorophyll and carotenoids in the chloroplast organelle are converted to excited electronic state, called excitons, by the photons. This conversion, no matter how effective, is still inefficient, as some of the excitons are converted back into photons as fluorescence, while some are lost as heat. For those that remain in the chloroplast, they drive the electron transport chain along the membrane proteins of the chloroplast, and produce a proton gradient between the membranes. This gradient, in turn, drives the production of adenosine triphosphate (ATP), w hich is necessary to drive the other part of photosynthesis that converts CO2 to carbohydrates (Whitmarsh and Govindjee, 1995). Phytochromes Aside from photosynthesis, light influences the plants on its other functions through molecules called phytochromes. The light-sensing portion (chromophore) of phytochromes has two isomeric forms, the red-absorbing (Pr) and the far red-absorbing (Pfr), with the former being the synthesized form and the latter instigating most of the plant developmental processes such as germination. Upon exposure of the seed and plant to light, especially red light, Pr is converted to Pfr (Campbell and Reece, 2002). According to Batty (1989), this mechanism ensures that wherever the seed falls, it will be germinating in a place with sunlight, which is needed for photosynthesis, as described above. In contrast, when it falls in a shaded soil, germination is delayed until, by some mechanical force, it is transferred to an area with more sunlight. Aside

Noise standard Essay Example | Topics and Well Written Essays - 250 words

Noise standard - Essay Example s of exposure that represent conditions under which it is believed that nearly all workers may be repeatedly exposed without adverse effect on their ability to hear and understand normal speech. Their TLV publications can be accessed through purchase since their publications have copyrights. ACGIH-TLVs do not have a legal force in USA; they are only recommendations/ guides and not regulatory limits due to individual susceptibility, hence ACGIH is not a standard setting body. Regulatory bodies view ACGIH’s guidelines as an expression of scientific opinion. ACGIH has several committees set up that decides which substance is to be selected for study and votes once a year on action terms. Each substance / element is selected based upon its availability, relevance and scientific data. ACGIH has established exposure guidelines for occupational exposure to noise in their Threshold Limit Values (TLVs), 85 dBA PEL with a 3 dBA exchange rate. ACGIH guidelines are used to measure workpla ce and personal noise exposure limits, assess risk of hearing loss, determine the need for hearing conservation program and identifying practical methods of controlling noise exposures. As compared to ACGIH’s guidelines, Occupational Safety and Health Administration (OSHA) a part of the USA’s Department of Labor (USDOL) publish Permissible Exposure Limits (PEL). PEL are regulatory limits enforced on all employers. These PELs were initially based on ACGIH TLVs in 1971. If OSHA determines the need for a specific standard it calls for advisory committees (ad hoc or standing) to develop recommendations. OSHA requires that when workplace exposures exceed 100% of the PEL i.e. exposure exceed 90dBA, feasible engineering or administrative controls must be deployed to reduce noise levels. Engineering control includes redesigning space and operations to reduce noise at source, transmission path or at receivers end. Administrative controls include scheduling and controlling the level of exposure