Ethylene-induced Pea Internode Swelling: Its Relation to Ribonucleic Acid Metabolism, Wall Protein Synthesis, and...

Area of Science:

• Plant Biology
• Molecular Physiology
• Biochemistry

Background:

• Ethylene is a plant hormone regulating various growth processes.
• Cell expansion is crucial for plant development, influenced by cell wall properties.
• Previous studies indicated ethylene's role in modulating plant tissue morphology.

Purpose of the Study:

• To investigate the physiological and molecular effects of ethylene on etiolated pea stem sections.
• To understand how ethylene influences cell wall composition and structure.
• To elucidate the mechanisms behind ethylene-induced radial swelling in plant tissues.

Main Methods:

• Exposure of etiolated pea (Pisum sativum L. var. Alaska) subapical sections to ethylene gas.
• Measurement of fresh weight changes and tissue swelling.
• Analysis of ribonucleic acid (RNA) metabolism.
• Quantification of (14)C-proline and leucine incorporation into cell wall proteins.
• Assessment of cell wall protein composition (proline-hydroxyproline ratio).
• Evaluation of cell wall microfibrillar orientation using optical birefringence.

Main Results:

• Ethylene exposure induced radial swelling in pea stem sections with minimal fresh weight increase.
• No significant effect of ethylene on gross RNA metabolism was observed.
• Ethylene inhibited the incorporation of proline and leucine into cell wall proteins after a 3-hour lag.
• Ethylene altered the proline-hydroxyproline ratio in cell wall proteins.
• Ethylene changed the cellulose microfibrillar orientation in the cell wall, as indicated by optical birefringence.

Conclusions:

• Ethylene disrupts normal polar cell expansion, leading to radial swelling in pea stems.
• The observed swelling is associated with inhibited synthesis and altered composition of cell wall proteins.
• Ethylene-induced changes in cell wall structure, specifically cellulose microfibril orientation, contribute to tissue swelling.