The factors affecting plant yield: light level
The factors affecting Zea mays, maize (C4) and Pisum sativa, or pea (C3) plant yield and growth patterns placed under shade and full sunlight were investigated. 20 plantlets placed into four vermiculite compost pots (5 from each plantlet) and submitted to fertilizer or no fertilizer. And after 4 weeks the results showed that maize grown in light with no fertilizer had a higher relative growth rate and root to shoot ratio indicating the allocation favoured root development. Meanwhile pea with fertilizer and no light had a higher growth rate and shoot was more allocated since this C3 plants were long. Introduction
All organisms sense and interact with their environment. This is particularly true of plants. Plant survival and growth is critically influenced by abiotic factors including water, wind, and light. But most importantantly (in our experiment) light as it physical alters temperature which directly affects photosynthesis, respiration, transpiration - loss of water and absorption of water and nutrients. The rate of these processes increases with an increase in temperature responses is different with different crops. The extent of growth and yield responses of plants to elevated CO2 depends on the photosynthetic pathway. Crops with C3 photosynthesis will respond markedly to increasing CO2 concentrations. Common C3 crops are small grain cereals (wheat, rice, barley, oat, and rye); grain legumes or pulses (soybean, peanut, various beans and peas); root and tuber crops (potato, cassava, sweet potato, sugar beet, yams); most oil, fruit, nut, vegetable, and crops; and temperate-zone (cool-climate) forage and grassland species. (Sionit et al,. 1981) In contrast, plants with C4 photosynthesis will respond little to rising atmospheric CO2 because a mechanism to increase the concentration of CO2 in leaves causes CO2 saturation of photosynthesis at current ambient concentrations. Common C4 crops are maize (corn), sugarcane, sorghum, millet, and many tropical and subtropical zone (warm-climate) grass species (Runion et al,. 2010).
The C4 photosynthetic carbon cycle is an elaborated addition to the C3 photosynthetic pathway. It evolved as an adaptation to high light intensities, high temperatures, and dryness. Therefore, C4 plants dominate grassland floras and biomass production in the warmer climates of the tropical and subtropical regions. In all plants CO2 is fixed by the enzyme Rubisco. It catalyzes the carboxylation of ribulose-1,5-bisphosphate, leading to two molecules of 3-phosphoglycerate. Instead of CO2, Rubisco can also add oxygen to ribulose-1,5-bisphosphate, resulting in one molecule each of 3-phosphoglycerate and 2-phosphoglycolate. Phosphoglycolate has no known metabolic purpose and in higher concentrations it is toxic for the plant. (Bingham, 1984) It therefore has to be processed in a metabolic pathway called photorespiration. Photorespiration is not only energy demanding, but furthermore leads to a net loss of CO2. Thus the efficiency of photosynthesis can be decreased by 40% under unfavourable conditions including high temperatures and dryness The unfavourable oxygenase reaction of Rubisco can be explained as a relic of the evolutionary history of this enzyme, which evolved more than 3 billion years ago when atmospheric CO2 concentrations were high and oxygen concentrations low. Apparently, later on, it was impossible to alter the enzyme’s properties or to exchange Rubisco by another carboxylase. Nevertheless, plants developed different ways to cope with this problem. Perhaps the most successful solution was C4 photosynthesis. (Runion et al,. 2010)
Material and methods
A trays of pea and maize seedlings (2 trays of each), 7 days old, grown in coarse vermiculite was issued. to experiment the comparison between treatments species, or within species under different growing regimes. Standard growing conditions in the growth room were ~27°C...
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