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Lysosomes of root tip cells in corn seedlings
1Department of General Botany, Swiss Federal Institute of Technology, Zürich.
Planta
|February 14, 2014
Summary
Corn seedling root tips contain distinct light and heavy lysosomes within the mitochondrial fraction. These lysosomes, differing in enzyme content and density, may represent developmental stages of the plant cell
Area of Science:
- Plant cell biology
- Biochemistry
- Cellular organelles
Background:
- Lysosomes are crucial cellular organelles involved in degradation and recycling.
- Identifying and characterizing different lysosome populations is key to understanding cellular processes.
- Plant root tip cells offer a model system for studying organelle development.
Purpose of the Study:
- To identify and characterize different types of lysosomes in corn seedling root tips.
- To investigate the enzyme content and physical properties of these lysosome populations.
- To propose a developmental model for the lysosomal apparatus in plant cells.
Main Methods:
- Cell-free extraction from corn root tips.
- Differential and density gradient centrifugation (sucrose and sorbitol media).
- Enzyme assays for acid hydrolases, transaminases, and oxydoreductases.
- Electron microscopy (frozen-etched tissue and isolated particles).
Main Results:
- Two distinct lysosome populations, light and heavy, were identified based on sedimentation properties.
- Light lysosomes (0.3-1.5 μm) resemble small vacuoles and contain transaminases and hydrolases.
- Heavy lysosomes (0.1-0.3 μm) have membranes similar to vacuoles and ER, with high oxydoreductase activity.
- Heavy lysosomes consist of at least three subpopulations with varying densities and enzyme profiles.
Conclusions:
- Light and heavy lysosomes represent distinct entities with different biochemical and structural characteristics.
- These lysosome types likely represent sequential stages in the development of the lysosomal system.
- The large vacuole in mature plant cells may be the terminal form of this developmental process.
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