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Early in the study of plant hormones, "phytohormone" was the commonly used term, but its use is less widely applied now. Plant hormones are not nutrients, but chemicals that in small amounts promote and influence the growth, [13] development, and differentiation of cells and tissues. The biosynthesis of plant hormones within plant tissues is ...
Tropic hormones are hormones that have other endocrine glands as their target. Most tropic hormones are produced and secreted by the anterior pituitary. [1]: 719 The hypothalamus secretes tropic hormones that target the anterior pituitary, and the thyroid gland secretes thyroxine, which targets the hypothalamus and therefore can be considered a tropic hormone.
Thus, a plant can (as a whole) react to external conditions and adjust to them, without requiring a nervous system. Auxins typically act in concert with, or in opposition to, other plant hormones. For example, the ratio of auxin to cytokinin in certain plant tissues determines initiation of root versus shoot buds.
The main release-inhibiting hormones or inhibiting hormones are as follows: The hypothalamus uses somatostatin to tell the pituitary to inhibit somatotropin and to tell the gastrointestinal tract to inhibit various gastrointestinal hormones. There are various other inhibiting factors that also have tropic endocrine inhibition activity.
In both cases, the directional growth is considered to be due to asymmetrical distribution of auxin, a plant growth hormone. [3] The term "tropism" (from Ancient Greek τρόπος (trópos) 'a turn, way, manner, style, etc.' and -ism) is also used in unrelated contexts.
For example, thyroid-stimulating hormone (TSH) causes growth and increased activity of another endocrine gland, the thyroid, which increases output of thyroid hormones. [34] To release active hormones quickly into the circulation, hormone biosynthetic cells may produce and store biologically inactive hormones in the form of pre-or prohormones ...
Plant physiology is a subdiscipline of botany concerned with the functioning, or physiology, of plants. [1]A germination rate experiment. Plant physiologists study fundamental processes of plants, such as photosynthesis, respiration, plant nutrition, plant hormone functions, tropisms, nastic movements, photoperiodism, photomorphogenesis, circadian rhythms, environmental stress physiology, seed ...
The hypothalamus produces the hormones oxytocin and vasopressin in its endocrine cells (left). These are released at nerve endings in the posterior pituitary gland and then secreted into the systemic circulation. The hypothalamus releases tropic hormones into the hypophyseal portal system to the anterior pituitary (right).
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