The Importance Of Plant Hormones

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Plant Hormones:
Hormone Locations (color coordinated and showing relative concentrations)
Auxin- Auxin is a hormone that’s main function is to promote cell elongation in stems, buds and roots and also plays a small part in the differentiation or new cells. Auxin is present in high concentrations in germinating fruits and seeds, but it is not yet known whether this high concentration of auxin is passed on from the mother or whether is is created but the developing tissues. Auxin also helps control what direction growth occurs. Plants “control” growth by changing the concentration of auxin in different regions. There is a higher concentration of auxin on the dark side of stems. The cells on this side of the stem then
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Cytokinin also regulates the growth of buds. Cytokinin acts in roots and stems, more specifically the meristems in these regions. Even though cytokinin acts in the growing stems, it is only produced in the roots. The roots cells must produce cytokinin that then travels up the xylem to other regions of growth throughout the plant. The receptors in for cytokinins are most commonly found in the ER. Since the receptors for this hormone are inside the cells, the hormone must be non-polar and small enough to fit across the membrane. Once the hormone has entered the cell and binded to its receptor, cytokinin stimulates the productions of proteins that are essential to mitosis. When the concentration of this proteins increases, it is more likely that there will be a favorable collision and a reaction will occur. In this way, cytokinin helps increase mitosis in growing regions of the plant. Similarly to Auxin, cytokinins also help with modifying apical dominance, but instead of promoting main stem growth it promotes lateral bud growth. Since cytokinins are such important growth hormones, the also play a part in beginning and continuing seed germination. Cytokinins also delay leaf senescence, the final stage of leaf development. Leaf senescence is when the leaves turn a different color, and transport all of their essential molecules back into the plant in preparation to fall. Cytokinins slow …show more content…
This process occurs in two different places in the plant’s reproductive structures, once in the male structures and once in the female structures. Male gametogenesis can occur in two stages of reproduction depending on the species of angiosperm. The first place that male gametogenesis can occur is while pollen is developing in the anthers of the male reproductive structures. If gametogenesis occurs at this time, once pollen grains are formed, the generative cell performs meiosis and two fully formed sperm cells travel in the pollen grain. The other time that gametogenesis can occur is after the pollen grain has landed on the receiving surface of the stigma. For more information read Pollination and Double Fertilization. In the female reproductive system, gametogenesis begins when mitosis occurs in the ovaries. In female gametogenesis, asymmetrical divisions during mitosis occur. This means that the cells are not divided equally. One daughter cell gets more cytoplasm than the other daughter cell, making it larger. This leads to accumulation of the cytoplasm in only one of the daughter cells. This larger daughter cell is known as the macrospore mother cell. The other daughter cells with smaller cytoplasms from uneven division eventually dissolve. The macrospore mother cell then forms a embryo sac within the ovules. Inside of this embryo sac, three further mitotic divisions occur,

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