Ultrastructure of Auxin‐induced Tumors of the Coleorhiza‐epiblast of Wheat

Abstract

When wheat is germinated in high concentrations of certain auxins, the coleorhiza-epiblast grows in an excessive and disorganized manner and resembles a callus. Wheat was germinated in 10 M indoleacetic acid or in water. There was greater net synthesis of DNA, RNA, and protein in the tumor tissue than in control tissue. Control and tumor tissue was fixed for electron microscopy 1, 2, 3, and 4 days after sowing. In contrast to the controls, many more lipoidal bodies appeared in 1-day-old, auxin-treated tissue and thereafter diminished in number. In 2- and 3-day-old tumor tissue, small membraneous fragments were prominent but disappeared in older tissue. With time, the following changes became progressively more pronounced: cytoplasmic vacuolation, appearance of myelin figures, polyribosome configurations and extensive profiles of rough endoplasmic reticulum, and sloughing of cytoplasmic contents into and accumulation of electron-dense material in vacuoles. Possible factors in susceptibility of certain tissues to tumor formation are discussed.

Culture surface and exogenous putrescine-altered shoot growth pattern in mannitol- and cadmium chloride-pretreated callus of Cymbidium Via del Playa “Yvonne”

“…Moreover, the possibility of putrescine acting like growth regulators especially like auxins cannot be ruled out. This assumption is quite in agreement with Walne et al (1975) who observed rough endoplasmic reticulum, dictyosomes, and lipoidal droplets while studying the ultrastructure of auxin-induced tumors of the coleorhizaepiblast of wheat. At this point, we would like to speculate that CPM from where the callus were obtained in our study before mannitol and CdCl 2 pretreatment contained a high concentration of 2,4-D.…”

Loss of Gravitropism in Farnesene-Treated Arabidopsis Is Due to Microtubule Malformations Related to Hormonal and ROS Unbalance

“…thaliana , resulting in malformation of the apical meristem. Moreover, as observed by Walne et al [ 69 ], high auxin levels strongly damage the cell ultra-structure resulting in cytoplasmic vacuolation, dictyosomes with swollen cisternae and strong production of vesicles. According to these results, the accumulation of endogenous auxin induced by farnesene in root resulted in strong ROS production, alteration of the cell ultrastructure and microtubules disorganization, accompanied by root malformation, anisotropic root growth and lack of root hair production.…”

QTL mapping of coleorhiza length in maize (Zea mays L.) under two germination environmental conditions

“…Previous studies have proposed that the coleorhiza surrounding the radicle provides protection to the quiescent meriste-matic tissue until the root becomes self-supported (Sargent and Osborne 1980). Moreover, the coleorhiza is considered as the first organ of the embryo contacting water and nutrient uptake to support embryo growth during germination (Howarth 1927, Price and Ey 1970, Walne et al 1975, Debaene-Gill et al 1994, Nishimura et al 2007). To the second event of the three-step maize germination, coleorhiza elongation breaking through the testa is the necessary and most critical step, and it is also likely to stand for ability to overcome the obstruction of testa to avoid the occurrence of the Ôtesta dormancyÕ phenomenon during maize seed germination.…”