The Role of Peroxidases in the Development of Plants

Peroxidases are isozymes—enzymes with different amino acid sequences that catalyze the same reactions—that reduce either hydrogen peroxide or molecular oxygen to make them less toxic in plants. Plant peroxidases are especially important in conferring salt tolerance to higher-order plants.

Salt stress reduces seed germination, disrupting the ability of the cotyledon to take up mineral ions essential to its growth. It alters gaseous exchange in leaves, and it destroys the plant’s machinery for photosynthesis. Young plants under salt stress cannot make the carbohydrates they need for normal growth.

Salinity, of course, has direct effects on crop yield. And as sea levels rise, salty water tables have an ever-increasing effect on the productivity of coastal farms.

Excessive salt leads to the breakdown of membranes in the plant. It leads to increases in reactive oxygen species and metabolic toxicity. The oxidative stress caused by salt stress generates superoxide anion (O2.-), singlet oxygen (1O2), hydroxyl radicals (OH), and hydrogen peroxide (H2O2). Peroxidases impose tight control on these destructive reactive species of oxygen without eliminating them entirely.

Peroxidases reduce hydrogen peroxide by oxidizing a variety of electron donors, including aromatic amines, fatty acids, phenols, lignins, and their secondary metabolites. Plant peroxidases are ubiquitous in plants. They may be found in the cell cytoplasm, in the cell wall, and in some organelles. They may be acidic or alkaline, ironic, covalently bound, or soluble.

Plant Phisiology Lab Experiements

You can introduce your students to the fascinating study of plant pigments with IND-32: Plant Pigment/Peroxidase Analysis. Students choose a variety of colored vegetables and extract peroxidases through cell lysis with a mortar and pestle. They then run electrophoresis against known samples of cytochrome C and hemoglobin-albumin proteins.

In IND-22: Characterization of Peroxidases in Plants, your students will develop a hypothesis that they will test in the lab with a variety of intact plants, roots, and stems, They quantify peroxidases with DOT-blot assay and spectrophotometric procedures, and they then characterize the peroxidases with gel electrophoresis. Students are given detailed instructions for presenting their findings as a scientific paper, conforming to the format and documentation standards for scientific publication.

With products from Modern Biology, you can take your students beyond the mere retention of vocabulary words and testable facts to understanding scientific methods and critical thinking.

Examples of student papers have included:

• Effects of salt stress on the levels, tissue distribution, and isoenzyme profiles of peroxidases in the turnip.
• Developmental changes in the corn stem as viewed by peroxidase types, amounts, and tissue location.
• Variations in peroxidase levels, tissue distribution, and isoenzymes in different regions of the carrot.

For forty years since Modern Biology Inc. was founded by Dr. John Anderson, we have followed the same fundamental pedagogical principles.

Every experiment manufactured by Modern Biology matches a clear and concise lesson, with notes to help teachers prepare for it. Teachers can also develop test questions from the lesson guide.

All experiment kit made by Modern Biology supports scientific thinking. Students test their hypotheses. They never just watch demonstrations. They are never limited to facts and vocabulary.

Modern Biology helps students develop the manual dexterity and note-taking skills that they will carry to future study and their careers. Modern Biology is developed by working scientists for future working scientists.

The Modern Biology kit includes all the reagents and test materials teachers need for their laboratory exercise. There are no ordering separate reagents, fussing about missing shipments, or checking out lab materials from the supply room. Modern Biology supplies the safe, non-toxic, reliable reagents and measurement materials you need for every laboratory exercise. And because every Modern Biology experiment is available at a fixed cost, it’s easier to budget your supply cost for each class for each school term.

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