Cell elongation gibberellins

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. 

In a wide spectrum of plant species and organs, gibberellin-induced cell elongation has been correlated with a predominance of transverse CMTs [15,83,111,113-118]. Conversely, when endogenous levels of gibberellins became depleted by means of specific inhibitors of their biosynthesis (e.g., ancymidol, 25,35 paclobutrazol), the CMTs then... 

Thus, phenolic compounds and morphactin - which inhibit cell elongation and cell division in higher plants -have no effect on biosynthesis of auxins and gibberellins in cultures of certain fungi. Their action seems to specific for higher plants. 

In contrast to the auxins and gibberellins, abscisic acid (ABA) and ethylene usually retard cell elongation. With some exceptions (Takahashi 1972, Gaither et al. 1975, Malik and Mehan 1975 a, Van Staden and Bornman 1970) ABA is inhibitory to growth (Addicott and Lyon 1969, Milborrow 1974). ABA inhibits stem and root elongation and counteracts the promotive effects of other substances on these organs (Rehm and Cline 1973, Kaufman and Jones 1974,... 

Mertz D (1966) Hormonal control of root growth. Plant Cell Physiol 7 125-135 Metzger JD, Zeevaart JAD (1980) Comparison of the levels of six endogenous gibberellins in roots and shoots of spinach in relation to photoperiod. Plant Physiol 66 679-683 Meyer RF, Boyer JS (1972) Sensitivity of cell division and cell elongation to low water potentials in soybean hypocotyls. Planta 108 77-87 Milborrow BV (1966) The effects of synthetic DL-dormin (abscisin II) on the growth of the oat mesocotyl. Planta 70 155-171... 

Odhnoff C (1963) The effect of gibberellin and phenylboric acid on xylem differentiation and epidermal cell elongation in bean roots. Physiol Plant 16 474-483... 

In most plants, the outstanding effct of the gibberellins is to elongate the primary stalk. This effect occurs in the young tissues and growth centers and is caused either by an increase in cell length, an increase in the rate of cell division, or a combination of both, depending on the specific type of plant treated. 

---