PNL Volume 14

1982

RESEARCH REPORTS 21

ABERRATIONS IN SHOOT MORPHOGENESIS OF PEA SEEDLNGS AFTER TREATMENT WITH

MICROTUBULE DISORGANIZERS AND 2.4-D

Ingensiep, H. W. Institute of Genetics, University of Bonn

Federal Republic of Germany

Microtubules are known to be involved in morphogenetic activities

on the cellular level and it can be assumed that genes that influence

the organization of microtubules may also influence the plant's

morphology. On the other hand, auxins are known to influence plant mor-

phology on the intercellular level, the auxin-herbicide 2,4-

dichlorophenoxyacetic acid (2,4-D) being especially noted for causing

abnormal growth (1). In a comparative study we treated young

pea seedlings with microtubule disorganizers and 2,4-D to determine

their morphogenetic effects on shoot development.

One-week-old etiolated pea seedlings were treated with the follow-

ing compounds: colchicine (5xlO~³M), vinblastine (100 ug/ml) and 2,4-D

10^-4M) dissolved in water. From 5-10 ul of each solution were applied

between the primary leaves of the apical hook. The seedlings were fur-

ther cultivated under a light/dark regime of 16/8 hours on moist

vermiculite to induce light-dependent morphogenesis. Under these condi-

tions the MT-disorganizers (colchicine, vinblastine) and the auxin-

herbicide 2,4-D, produced different morphological changes in the shoot.

Within one week after treatment the colchicine-treated population ex-

hibited aberrations ranging from strong swelling in the apical tissue of

clearly inhibited seedlings to abnormal leaf formation in slightly fur-

tner developed seedlings (Fig. 1a). Deviations in leaf shape were

common in this population. For example, one of the stipules was often

a sent, reduced in size, or altered in shape. The leaflet blades also

differed in size, shape, and conformation. The stems were thickened or

broadened toward the tip similar to fasciated structures. Nevertheless

leaves and stems were green and growth was not at all inhibited.

The vinblastine-treated seedlings showed similar but less striking

aberrations in shoot development, and shoot morphogenesis in general was

only slightly inhibited (Fig. 1b).

The 2,4-D-treated seedlings were not so drastically Inhibited, but

several morphological aberrations were evident (Fig. 1c). Again, the

leaf blades were abnormal in size and shape, but not in color. Apical

leaves often showed extremely disturbed morphogenesis, e.g. blade curva-

ture and stem broadening. The stipules were not affected so strongly,

but they did show changes in size and shape similar to seedlings treated

with colchicine.

These preliminary investigations demonstrate that the light-

dependent morphogenesis of young pea seedlings is affected substantially

by MT-disorganizers and by 2,4-D. Both compounds induced similar abnor-

malities in leaflet, stipule, or stem formation, thus supporting the

view that microtubule organization within the plant cells may be

directed by auxins.

1. Audus, L. J. (ed.) 1 964. Physiology and Biochemistry of

Herbicides. Academic Press, London.



22	PNL Volume 14	1982	RESEARCH REPORTS



Fig. 1. Leaf aberrations pea seedlings with: 2,4-D.			resulting from treating one-week-old (a) colchicine, (b) vinblastine, or (c)