Workshop 2 Hypotheses and Predictions The US cotton industry is dealing with inc

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Workshop 2 Hypotheses and Predictions The US cotton industry is dealing with increased competition from foreign cotton markets. To remain competitive in this textile on a world-wide basis, US cotton growers need to find ways to increase crop yield (the weight of cotton produced per acre- both fiber number and fiber weight) and crop quality (increases in fiber length, wall thickness). 20 30 40 Age (DPA) Figure 1: Increases in fiber length over time in several Figure 2: Changes in fiber number per ovule in several The Observations from the literature . IAA and GA are hormones common to all plants . IAA functions to increase cell division, increase the development of specialized cells . GA functions primarily to enhance cell growth (expansion) . Cotton ovaries exhibit an increase in IAA levels coincides with the timing of fiber initiation, then IAA levels drop, only to increase after 4 DPA In cotton ovules, GA levels rise at about 8 DPA (elongation phase) An analysis of fiber growth (Figure 1) indicates that several different cotton varieties exhibit similar increases in fiber length during development. . An analysis of fiber initiation (Figure 2) indicates that several different cotton varieties exhibit similar increases in fiber number per ovule over time. Previous literature indicates that during fiber development there are changes in the levels of the hormones Gibberellic Acid (GA) and indole acetic acid (IAA) Homework Assignment Generate 3 different hypotheses that you could test regarding the possible use of GA and IAA during fiber development to improve either cotton yield or quality. For each hypothesis generate a prediction.

Explanation / Answer

It has been reported that GA mainly promotes ovule growth while IAA is largerly responsible for fiber growth.

According to last observation, there are changes in level of these two hormones before anthesis (period of flowering) , during anthesis and after anthesis.

1. It has been seen that the level of Indole acetic acid decreases before the flowering period, and as this hormone plays a important role in cell division and cell elongation and therefore, plant growth. So, if we can supply the cotton plant with continous amount of IAA, then there are chances that the fiber length and weight will become appreciable.

2.Now, talking about the hormone Gibberlic acid, which can stimulate rapid stem and root growth. Literature says that GA is entitled towards the vegetative growth more. So if we alter the GA metabolism so that less of the GA plant hormone is available to the plant, it will lead to reduced leaf area and plant height, and if applied to the top it will quickly move within the plant to young leaves, branches and internodes for effective control of new growth, because it directs more food and energy toward fruit development rather than vegetative growthdue to which fiber quality is improved and yield potential is increased.

3.The last and final hypothesis that can be made on previous literatures is that when IAA biosynthesis is increased in the ovules epidermis, it leads to improved fiber cell numbers and therefore final quality and yield. This is because, there is an increase in percentage of lint fibers which directly corresponds to fiber yield. Therefore, if we can increase the biosythesis of IAA in ovules, it will lead to better fiber quality.

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