Effects of Plant Nutrient Deficiency free essay sample

This experiment aimed to determine the effects of nutrient deficiency on plants. This was done by examining tomato plants grown in a medium that contained all the nutrients needed to survive and comparing those results to plants that were grown in nutrient deficient mediums. The biomass and standard chlorophyll content were the focus of the experiment. The biomass was measured by taking the mass of the plant. The standard chlorophyll content was measured by taking the absorbance of the leaf acetone solution. The results were significant for biomass but were only significant for the distilled water treatment. Nutrient deficiency has an effect on the biomass of plants, but we fail to reject the hypothesis that the standard chlorophyll content of the nitrogen, iron, and phosphorus deficient plants is no different than the SCC of the plants placed in a medium that contained all the nutrients needed to survive healthily. Introduction The purpose of this laboratory was to examine how deficiencies in nitrogen, phosphorous and iron affect tomato plant growth. Distilled water was also used as a medium to grow the tomato plants in. There are many minerals and organic molecules that are obtained through the soil that plants need to survive. These are transported through the roots of the plant when water is absorbed (Helms et al. 1998). Plant nutrient deficiencies can have many effects such as stunted overall growth of the plant, or chlorosis and necrosis of certain plant parts, such as the leaves. One of the features that plants possess is the ability to take nutrients from older tissue and move it to newer tissue. This notion can be visualized. Kosinski states that if there is an inadequate amount of a mobile element, older plant tissue will show symptoms of the deficiency first. Old leaves may become yellow and appear dead (Kosinski 2012). Nitrogen and phosphorus in this lab were considered to be mobile elements. However, if the element in inadequate amounts is immobile, the symptoms will appear first in new foliage. Iron in this experiment was considered an immobile element. Tomato plants were used in this experiment because they can be easily grown inside the lab and display obvious symptoms of nutrient deficiency (Kosinski). The plants harvested in the lab were currently in the vegetative growth stage and did not have any flowers or fruit growing. Therefore, increase in mass during this stage is due solely to the growth of the foliage (Kosinski). The biomass and the SCC values were calculated based upon the leaves of the plants in the following treatments. The first treatments were the tomato plants grown in the complete medium, containing all macronutrients and micronutrients. These treatments acted as the control for the experiment. The independent variables are the deficiencies. There were plants grown in nitrogen deficient medium, phosphorus deficient medium, iron deficient medium, and in distilled water. The dependent variables for this experiment are biomass and standard chlorophyll content. Nitrogen is most commonly deficient in plant soils even though it is the most abundant gas in the atmosphere. This occurs because plants can only used fixed nitrogen. Nitrogen, a macronutrient, is very significant in plant growth. It has many roles in proteins and nucleic acids, as well as other macromolecules. It also makes up 1-5% of plant dry weight (Kosinski). Nitrogen deficient plants therefore are usually smaller. This is due to hormonal effects of nitrogen deficiency. Cytokinin synthesis is retarted and abscisic acid is accelerated (Kosinski). These hormonal changes age the plant and reduce the tomato plant’s lifespan. Tomatoes grown in a nitrogen deficient environment are usually rigidly upright, with thin stems and small leaves and branching is reduced (Kosinski, Berry). The leaves first change to a pale green color and then become yellow under extreme deficiency (Berry). The leaves wither away after becoming yellow and flowers fall before normal harvest time (Kosinski). Chlorosis, which is the term used for the yellowing, is more prominent between the veins as opposed to along them. Therefore, the null hypotheses for our experiment are: As compared to the control tomato plants, the plants grown in a nitrogen deficient environment will have the same biomass over four weeks, and the plants grown in this environment will also have the same standard leaf blade chlorophyll content of those grown in the complete medium. The research hypotheses are: The plants grown in a nitrogen deficient environment as compared to those grown in the complete environment, will have a smaller biomass and SCC. It is predicted that these plants will be stunted, having a smaller biomass, and the leaves will lose their color and become yellow, having a lower SCC. Phosphorus, another element used in this experiment, is the second most depleted nutrient in soils. Phosphorus is used in phospholipids and in membranes and also plays a part in other hereditary and metabolic functions. Therefore, phosphorus may restrict cell reproduction, inheritance, and normal metabolism (Kosinski). The symptoms of this deficiency are usually difficult to identify, but a major visual symptom is the plants are dwarf sized (Berry). These plants that are grown in inadequate amounts of phosphorus usually develop more slowly than other tomato plants in the same environmental conditions with the exception of the phosphorus deficiency (Berry). These plants are sometimes mistaken for young unstressed plants. Some plants recycle the phosphorus and can live many years without growth, and respiration rates in these plants tend to be higher (Kosinski). Tomato plants are extra sensitive to the lack of phosphorus and tend to display purpling of the stem and the underside of the leaves. Similarly to nitrogen, this is a mobile macronutrient. The null hypotheses are that as compared to the complete tomato plants, those grown in the phosphorus deficient environment will have the same biomass over the four-week growth, and these plants will also have the same standard leaf blade chlorophyll content as those in the complete medium do. The research hypotheses are that the plants grown in the phosphorus-depleted environment will have a smaller biomass and smaller SCC as compared to the tomato plants grown in the complete medium. It is predicted that the plants will have stunted growth, having a smaller biomass than those that are grown in a medium that contains all the macronutrients and micronutrients needed. The SCC value is also predicted to be smaller than that of the plants in the control because they become discolored. Iron is the only micronutrient in this experiment and it is an immobile element. It has to be taken in continuously and is significant in plant’s protein and enzymes that participate in electron transport (Kosinski). Iron also functions in chlorophyll and protein synthesis. Because this element is immobile, the newer leaves deteriorate first (Kosinski). The youngest leaves go through chlorosis first, evolving into total chlorosis and then these leaves become completely bleached (Berry). Lower metabolic rates are associated with iron deficiency because of iron’s role in respiration. The null hypotheses for this treatment are: When compared to the tomato plants grown in the complete medium, iron deficient plants will have the same biomass over the four week growth period, and these plants grown in iron deficient medium as compared to those in the complete environment will have the same SCC. The research hypotheses are that when compared to the plants grown in the complete medium, those grown in the iron deficient medium will have a smaller biomass, and a smaller SCC because the leaves of these plants become deteriorated and bleached. The last treatment used was distilled water. The plants grown in distilled water tend to have purple leaf veins. The null hypotheses for this treatment are: As compared to the plants grown in the complete medium, the plants grown in the distilled water will have the same biomass over 4 weeks, and will also have the same SCC as those grown in the complete environment. The research hypotheses are: The plants grown in distilled water when compared to those grown in the complete environment will have a smaller biomass and a smaller SCC. It is predicted that these plants will be smaller because they are not receiving the nutrients needed to survive. The leaves are not receiving these nutrients and are expected to become discolored and have a smaller chlorophyll content. Materials and Methods The steps provided in the Plant Nutrient Deficiency OMP, and the Procedures for Harvesting Tomatoes OMP (Kosinski 2012) were used in order to complete our experiment. The lab was divided into groups in order to have plants for each of the five treatments. The two plants were massed and one of the plant’s leaves were then cut off and also massed. The leaves were crushed with a mortar and pestle along with acetone. The resulting solution was placed in a tube, was subjected to a centrifuge and the solution’s absorbance was measured at 663 nm. If the absorbance value was over 1, the solution was diluted by using 9mL of acetone and 1mL of the solution. Different equations were used to calculate the standardized chlorophyll content (SCC) of the leaves based upon whether the solution was diluted or not. The second plant was placed into a black plastic cup along with Hydroton pellets and immersed into water that was either nitrogen deficient, phosphorus deficient, iron deficient, complete, or in distilled water (the five treatments used in this lab). Four weeks later, the SCC values of this plant’s leaves was calculated using the same method as previously mentioned.