November 28, 2004


Breed Improvement Through Plant Hormones

* This article is under copyright protection.

Manabu Akaike
Universal Design Intelligence Inc.

Plant life as a source of food and as a resource for absorbing carbon dioxide in the atmosphere is critical for the future comfort of the human race. The Institute of Physical and Chemical Research (Riken) is conducting research into plant hormones, not in the controversial genetic modification field, but in a search for ways to improve plant varieties and regulate growth. Riken research has already yielded some important results.

There are actually only seven types of substances known to be plant hormones. Plants combine these seven substances in different ways to regulate growth. The most interesting one for researchers now is one of the latest to have been identified, brassinolide.

The Riken team was the first in the world to develop a substance that inhibits biosynthesis of brassinolide, and by thus eliminating one of the key elements in the plant's array of hormones, made it possible to analyze the way the plant used hormones to regulate growth.

Plants that had been treated with this inhibitor were rendered unable to produce brassinolide. Dicotyledonous or two seed leafed plants like cucumbers or peas were observed to grow remarkably smaller, particular in height. Leaves of plants that had been treated with the inhibitor also exhibited a markedly darker green color. Usually, when plants are raised in dark rooms, they develop extremely leggy stems and sprouts, but when brassinolide is suppressed, the seed leaves open up fully, growing as if they were being raised in a perfectly sunny place. It's thought that this evidences the effect of brassinolide on the rubisco gene that senses light. This technology could be applied in plant cultivation in regions that tend to lack sunlight.

If we can regulate plant growth by adjusting the balances of plant hormones, we may be able to establish technology that would allow us to harvest just the necessary amount of any particular crop. For example, if we are able to establish a shortened rice cultivation cycle that takes just two months from planting to reaping, attacks by weeds and pathogenic bacteria would not be able to keep pace with the growth speed of the rice, and pest outbreaks could also be avoided, so that we would no longer have to use large quantities of agrochemicals to ensure a good harvest.

Creating Atavistic Mutations by Irradiation with Heavy Ion Beams

Heavy ion refers to the ionized nucleus of an atom that has been stripped of electrons through electrical discharge. These heavy ions are beamed into cells using a high-speed irradiator known as a cyclotron. The heavy ion beam cuts off the DNA of the cell, resulting in a genetic deficit type of spontaneous mutation. In experiments using tobacco plants, researchers were successful in creating an albino tobacco without chloroplasts.

Evolution is a process through which new genes are continually added. The starting point of the current Riken research was an attempt to find a way back through the evolutionary path, not by recombining genes, but by shaving off genes using heavy ion beams. The research aims to turn evolution back on itself and induce atavistic or throw-back mutations.

The rice pictured here shows the effect of irradiation with heavy ion beams inducing an atavistic reaction, as is seen in the "beards" growing around the grains. This rice is similar in appearance to old types of wild rice. Surely ancient Japanese ate a rice very similar to this one.

Tobacco is a plant that is easily damaged by salt, but after irradiation with heavy ion beams, the plant was able to withstand a 2% salt water solution. If this can be brought up to a 3.5% salt solution level, it would become possible to cultivate tobacco in sea water. This type of technology has great potential in terms of the effort to realize so-called marine agriculture, where rice and other crops could be raised on the ocean.

It's not about creating new organisms, but about reviving varieties that existed in the past. It's an effective application of what has been called "passage of time technology," meaning science that has evolved naturally over long periods of time, and that has been fully tested for safety and function by our earth and mother nature. This type of technology is a high-tech application that requires the time and physical effort of low-tech applications, but I believe it suggests major possibilities for the coming future of low cost, high yield organic farming.

JAPAN CLOSE-UP, November 2002, published by PHP

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