Sample Agricultural Studies Essay Paper on Physiology of Plant Production

Physiology of Plant Production

    1. Electrical conductivity (of nutrient solution)- It is a measure of the strength of a nutrient solution. It provides data on the general fertility level of the nutrient solution and whether salinity problems are likely to exist.
    1. Air porosity- This is the air volume (%) in a given mass of substance.
    1. Cation exchange capacity- This is the capability to hold exchangeable cations, expressed as a sum of all the exchangeable cations that a substrate can absorb.
    1. Water potential- Is defined as the chemical energy per volume of water and includes osmotic potential, pressure potential, and matric potential. It is proportional to the variance between the chemical potential of water in solution and that of pure water.
  • Anions: Boron, chlorine, molybdenum, nitrate, phosphorous, sulfur, manganese

Cations: Ammonium, potassium, calcium, iron, magnesium, copper, zinc

  • When the solution temperature increases, the dissolved oxygen concentration reduces systematically as the air porosity is reduced by the heat.
  • The NO3 and NH4+ ratio have significant effects on plant growth and solution pH, while in some plant species, the ratio is at an optimum to enhance growth. In some, the NO3N leaches very easily from the container, bringing an imbalance. The importance of cognizing the effect of the ratio is that it will lead to a prevention of toxicity. While plants can grow with only NO3as a source of nitrogen, a high concentration causes an increase in pH which may be harmful while high NH4N leads to high toxicity in plants. While assessing the effects, however, care must be taken since different substrates have different compositions. Perlite and vermiculite, for example, have varying water holding capacity, cation exchange capacity, and pH, which affects the effects differently.
  • EC increase: Tomatoes have a high NO3 intake hence they absorb a lot of nitrogen, which is later released after building up. It is consequently more than that in the inflow solution.   
  • pH increase: Using NO3 as the only source of nitrogen causes the solution pH to increase to a greater extent, hence the subsequent increase in the pH of the efflux solution.
  • Volume decrease: Transpiration occurs through the leaves while some volume of water is retained in the plant, leading to a low volume in the efflux solution. Some discharge is also needed to avoid ion accumulation, which makes it less efficient in water use than other soilless culture systems especially since in this case no nutrient recycling is introduced.
  • BER under high VPD and high radiation- Under too high VPD and high radiation, there is excess transpiration. The roots do not get to absorb sufficient calcium, and the water intake is not sufficient. The fruits thus do not get enough nutrients, which leads to BER.
  • BER under high EC- Under high EC in the nutrient solution, the xylem flow to the fruit is suppressed due to a high salts concentration in the root zone which causes the availability of Ca to the fruit to decrease, leading to BER.
  • Photoassimilates move within the plant from the source to the sink. Since fruits are a sink, they share the photoassimilates almost evenly among the number of sinks, which reduces the amount of assimilates that each fruit gets. Pruning leads to the number of sinks being reduced, and correspondingly, a higher proportion of the photoassimilates is directed to each of the remaining fruits thus, increasing their size.