Modification by Ethylene of the Cell Growth Pattern in Different Tissues of Etiolated Lupine Hypocotyls

Abstract

The influence of ethylene on growth in etiolated lupine (Lupinus albus L.) hypocotyls was studied in ethephon-treated plants. Ethephon reduced the length and increased the diameter of hypocotyls. At the end of the hypocotyl growth period (14 days), the fresh weight was reduced by 53%, and the dry weight was reduced by 16%. Thus, ethylene reduced water uptake in the tissues to a greater extent than the incorporation of new materials. Light microscopic measurements showed that the thickness of tissues was stimulated by ethylene, the vascular cylinder and cortex exhibiting greater increases (55 and 45%, respectively) than pith (26%) or epidermis (12%). Ethephon modified the cell growth pattem, stimulating lateral cell expansion and cell wall thickness, while reducing cell elongation. The response to ethylene varied in the different tissues and was higher in cortex and pith cells than in the epidermis cells. The ethylene-induced cell expansion in the cortex varied according to the localization of cells in the tissue: the central and subepidermal layers showed little change, whereas the innermost layers exhibited the greatest increase. Electron microscopy revealed that ethylene increased both the rough endoplasmic reticulum and dictyosomes, suggesting that ethylene stimulated the secretion of cell wall materials. In untreated seedlings, the pattem of cell growth was similar in cells from the epidermis, cortex, and pith. The final cell size varied along the hypocotyl, the cells becoming shorter and broader the closer to the basal zones of the organ.Several recent studies have confirmed that growth in heterogeneous multicellular systems, such as coleoptiles or hypocotyls, involves the cooperation of functionally different tissues (7,8,18,19 morphometric studies showed that variations in cell growth rate as well as in cell wall thickness correlated with the variations of IAA content during lupine hypocotyl growth ( 13,14,23). These results suggest the participation of IAA in the control of cell growth in lupine hypocotyls.In addition to IAA, the influence of ethylene in the growth of stems is widely documented (for reviews, see refs. 1, 3, 15-17, and 21). Cell growth response to ethylene depends on the type of cell ( 16) as well as the cell's sensitivity to ethylene ( 12,15,21). Although some data suggest that cell responsiveness to ethylene could be mediated by the endogenous level of IAA (15,26), there is little information concerning the role of the different tissues in the ethylene-mediated growth of stems, unlike the case of IAA, which has been extensively studied.In a previous paper, we reported that lupine hypocotyl growth was inhibited by exogenous ACC2 and ethephon, the response being dependent on the concentration, age of the seedlings, and the localization along the hypocotyl (12). In addition, an extensive study showing variations in ethylene production, ACC content, and ethylene-forming enzyme activity during hypocotyl growth was carried out recently (20). From the above, some role for the ethylene ...

Ultrastructural changes and diosgenin content in cell suspensions of Trigonella foenum-graecum L. by ethylene treatment

“…These results are in accordance with those obtained for this growth regulator in different plant materials Sa´nchez-Bravo et al 1992).…”

“…A similar effect has been described for ethylene in other plant materials (Sargent and Osborne 1975;Liebermas et al 1983;Sa´nchez Bravo et al 1992).…”

Cloning, genetic mapping, and expression analysis of an Arabidopsis thaliana gene that encodes 1-aminocyclopropane-1-carboxylate synthase.

“…Physiological data have documented the role of ethylene in inhibition of cell elongation and subsequent determination of cell size and shape in etiolated seedlings (32,33). Nevertheless, our knowledge on the role of ethylene in development from the young seedling to a mature plant remains extremely poor.…”

Cell length instead of cell number becomes the predominant factor contributing to hypocotyl length genotypic differences under abiotic stress in Medicago truncatula

“…Regarding seedling shoot, hypocotyl elongation in the dark is due to both cell division and cell elongation in some species such as lettuce and sunflower (Galli , Heupel and Kutschera , Kutschera and Niklas ), while it is exclusively due to elongation of cells whose number is pre‐established in the embryo for others species, e.g. A. thaliana, M. truncatula and white lupin (Sánchez‐Bravo et al , Gendreau et al , Raz and Koornneef , Pierre et al ). It is noted that epidermis plays a crucial role in organ elongation, for leaves (MacAdam et al ) and for stem including hypocotyl (Kutschera and Niklas , Kutschera ).…”