Effects of cadmium and lead on the ultrastructure of root meristems and nodules of mungbean (Vigna radiata L. var. Pag-asa l)

Date

3-1999

Degree

Bachelor of Science in Biology

College

College of Arts and Sciences (CAS)

Adviser/Committee Chair

Nina M. Cadiz

Abstract

Mupas, Rosette F. , University of the Philippines Los Banos, Bachelor of Science in Biology , March 1999. EFFECTS OF CADMIUM AND LEAD ON THE ULTRASTRUCTURE OF ROOT MERISTEMS I) NODULES OF MUNGBEAN Vigna radiata L. var. Pag-asa I ). Adviser . Dr. Nina M. Cadiz One month old mungbean plants ( Vignrr radium L. var Pag-asa I ) were treated with two levels (10 mM and 40 mM ) of cadmium (Cd) and lead (Pb) for two weeks After 1 months mungbean plants were harvested. Nodules and root tips were collected , fixed. and prepared for microscopy Visual observations showed that 10 mM and 40 mM Cd and Pb concentrations caused stunted growth, inhibited root growth, reduced the extensiveness of the root system, the occurrence and, size of root nodules, and resulted to leaf chlorosis, The most severe effect was caused by 40 mM Cd where the plants died one week after treatment. Root tips in the present study showed two possible metal toxicity recovery strategies. First one is by lateral growth, secondly, via the root meristem recovery by the quiescent center giving rise to new meristem and root cap. These mechanisms help the plant cope up with the stress brought about by the presence of the heavy metals Transmission Electron Microscopy (TEM) results showed that the heavy metals appeared as electron dense granules in plant cells In the meristematic cells Cd was localized in the cell wall and cytoplasm while Pb was found only in the cell wall Both Cd and Pb was compartmentalized in the peribacteroid membrane as well as in the peribacteroid space of bacteroids in the nodules. The size and number of the bacteroids can be used as criteria for metal tolerance. At 10 mM Cd, 10mM and 40 mM Pb the bacteroids are reduced in number as well as the area the occupied. The results of this study suggest that the mechanisms of metal tolerance of mungbean (Vigna radiata L. Pag-asa I) could be attributed to the localization of the heavy metals in various parts of the cells in both roots and modules.

Language

English

Location

UPLB Main Library Special Collections Section (USCS)

Call Number

Thesis

Document Type

Thesis

This document is currently not available here.

Share

COinS