Quiescent centre

Quiescent Centre Meristematic Region Transition Zone Elongation Region... 

Orientation of CMTs in ditferent regions of the root cap, as well as the quiescent centre (QC), of in vitro cultured tomato roots which are either wild-type or gib-1 mutant. The root cap probably controls division planes elsewhere in the root these are abnormal in the gib-1 apices [136]. MT orientations were scored as transverse (T), longitudinal (L), oblique (O) or random (R) with respect to the major axis of cell growth. Percentage values are given as pairs (ala), the first value being from wild-type, the second from gib-1 roots, n is the number of ceils scored. Unpublished data of P.W. Barlow and J.S. Parker... 

Fig. 4. Effects of high (10 ppm and 100 ppm) ethylene treatment (24 h) on MTs in cells of cv. LG-11 maize roots. 10 ppm treatment (a-e) has no effects in cells of the quiescent centre (QC) (a) and in meristematic cells of root cap (RC) (a.b), but it depletes MTs from developmentally older root cap cells (b). In addition this ethylene treatment randomizes CMTs in all postmitotic cells of the root proper. For the outer cortex (CXI) and epidermis (EP) cells, this effect is only slight (c). However, cells of the inner cortex (d,e) are strongly affected in this respect and the transverse CMTs are replaced by completely random CMTs. 100 ppm ethylene treatment (f,g) disintegrates MTs from most root cells with the exception of the distal part of meristem and root cap initials and quiescent centre cells (not shown). In the root proper, the epidermis (EP) and outer cortex (OC) cells are the only ones to preserve their MTs which, in the case of epidermis, are still transverse and well-ordered (f). In contrast, the inner cortex cells (IC) are devoid of MTs (g). For more details on ethylene treatments see [157]. Bar represents 10 pm.

The questing finger of cloud lost its vigour, and slowly bowed over in defeat, its glowing vapour reabsorbed into the now quiescent centre of the shroud. The leading edges continued their advance. 

Watanabe T, Kondo N (1976) Isolation of a proteinaceous inhibitor of ethylene biosynthesis from marine algae. Agric Biol Chem 40 1877-1878 Webster PL (1967) Cell cycle kinetics in meristems Effects of colchicine and lAA. PhD Thesis, Case-Western Res Univ, Cleveland, Ohio Webster PL, Langenauer HD (1973) Experimental control of the activity of the quiescent centre in excised root tips of Zea mays. Planta 112 91-100 White KL, Hill AC, Bennett JH (1974) Synergistic inhibition of apparent photosynthesis rate of alfalfa by combinations of sulfur dioxide and nitrogen dioxide. Environ Sci Technol 8 574-576... 

Fig. 9.1. Diagrammatic median section of the root apex of Zea mays (maize). The sites of the initial cells of the promeris-tem are indicated by dots. E, piliferous layer C, cortex S, stele Q, quiescent centre R, root cap. (Drawn by Dr. L. Clowes, from H. E. Street, as Fig. 7.3.)...

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