Gibberellin auxins

Compounds other than nutrients which afTect physiological processes in plants. E.g. auxins, gibberellins. 

In addition to inhibitory chemicals which enter the plant from the external environment, many endogenous inhibitors appear to function as regulators of seed germination and plant growth and development. The interrelationships between endogenous inhibitors and growth promoters such as the auxins, gibberellins, and kinins remain to be elucidated. 

FRET-based nanosensors have been successfully used to monitor steady state levels of metabolites, nutrients, and ions in mammalian cells [74, 87], Recently FRET-based glucose, sucrose, and amino acid nanosensors have been developed to study the metabolism of glucose, sucrose, and amino acid uptake and metabolism in plant cells [80,89, 91]. The enormous potential of these nanosensors will be crucial for understanding ion (e.g., calcium), metabolite (e.g., sugars), hormone (e.g., auxins, gibberellins etc.), and nutrient (e.g., nitrogen, potassium, phosphorus) requirements and homeostasis in living plant tissues. 

Ethylene as a stimulator of growth and development. The most observed actions of ethylene on growing plants involves growth inhibition, or acceleration of senescence. These actions are especially evident in the antagonism or opposition of ethylene to auxins, gibberellins and cytokinins (27), as already outlined above. Actually ethylene stimulates growth in many types of cells, especially in water plants (Table II). When ethylene acts to stimulate cell elongation, as in water plants, auxins and CC>2 enhance the ethylene effect (38,39). This interaction is the reverse of that observed on land plants wherein ethylene opposes the effects of auxin, GA3 and cytokinins. 

Without in any way diminishing the importance of ethylene in the control and regulation of ripening and aging, I emphasize the critical supplemental importance of auxins, gibberellins, and... 

At the preclimacteric stage of development, just prior to the rise in ethylene production the concentrations of auxins, gibberellins, and cytokinins are assumed to be very low. 

Ephritikhine, G., Fellner, M., Vannini, C., Lapous, D. and Barbier-Brygoo, H. (1999) The saxl dwarf mutant of Arabidosis thaliana shows altered sensitivity of growth responses to abscisic acid, auxin, gibberellins and ethylene and is partially rescued by exogenous brassinosteroid. Plant., 18,303-14. 

In contrast to complex auxins, gibberellins, and cytokinins, ethylene is a simple gaseous compound. In 1932, it was discovered that ethylene would promote flowering in pineapples. The subsequent discovery of the role of ethylene in fruit ripening has been of considerable commercial importance in the banana and citrns industries. 

Chloro-3-methyl-4-nitro-lH-pyrazole (Release) has no auxin-, gib-berellin-, or cytokinin-like activity, yet it is an ejffective abscission agent. At the present, there is no evidence to indicate that Release retards auxin, gibberellin, or cytokinin activity. It does stimulate and enhance the tissue production of ethylene (105). Release is fairly stable, and there is no indication that it is degraded by the tissue to ethylene per se (106). 

Figure 1. Effects of CaCl2 on bioassays for auxin, gibberellin, and cytokinin. A effects of CaCl2 on elongation of oat coleoptile sections in the presence and absence of indoleactic acid B effects on elongation of lettuce hypocotyls in the presence and absence of gibberellic add and C effects on enlargement of Xanthium cotyledon pieces in the presence and absence of benzyladenine (13).

J.H. Yopp, Southern Illinois University, Carbondale, became interested in the brassins project in its early stages (36) and he conducted cooperative brassins studies with both Mitchell and Mandava. Yopp et al. (37, 38) evaluated brassins responses in a number of auxin, gibberellin, and cytokinin bioassays and showed that brassins responded similarly to some of the known hormones in certain systems but not in others. These studies led to more cooperative investigation of brassinolide and other brassinosteroids (39, 40). 

Until the discovery of brassinolide by USDA scientists in 1979, it was thought that only five groups (indole auxins, gibberellins, cytokinins, abscisic acid, and ethylene) of hormones were responsible for regulating plant growth and development. Following this discovery, a number of compounds similar to brassinolide both in structure and physiological activity were isolated from different parts of plants. On the basis of published... 

Fitting s attempt to identify his "Pollen Hormone" chemically was unsuccessful. Today, however, we know that pollen tissues are the source of the known plant hormones (auxin, gibberellins, cytokinin), as well as "brassinolide."... 

There are five groups of plant-growth-regulating compounds auxin, gibberellin, cytokinin, ethylene, and abscisic acid. For the most part, each group contains both naturally occurring hormones and synthetic substances. 

In addition to the well known major groups of plant hormones, the auxins, gibberellins, cytokinins, abscisins, and ethylene, without any doubt, some further classes of hormones seems to be present and active in plants and will be discovered or described in more detail in future. In this connection, for example, acetylcholine, the so-called brassins and anthesins, cyclic AMP as well as steroidal plant hormones are still under discussion. 

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