Study reveals startling new role for the plant hormone auxin

A team of scientists from the University of California, Davis discovered something new about the hormone auxin in plants. They found that auxin acts as a morphogen which directs the pattern of cell development based on concentration.

Plants reproduction system is located within its flower, where pollens produce sperm cells while egg cells are in the ovule. During the development stage, the ovule will undergoes both meiosis and mitosis several times. This resulting in a structure of embryo sac together with the production of 8 nuclei and three of them are positioned near the opening of the ovule. Figure below shows the position of 8 nuclei in the embryo sac.

Caption: A gradient (red) in the concentration of the plant hormone auxin, determines that only one of the eight undifferentiated nuclei in a plant's embryo sac will become an egg. (In this image, a large vacuole dominates the central section of the embryo sac.)

Credit: Monica Alandete-Saez/UC Davis

The studies discovered that the only nuclei that receive most hormone auxin will continue to develop into egg cell and later to be fertilized with sperm cell. Based on their observation, the hormone auxin is concentrated nearer to the opening of the embryo sac. Thus, the nucleus that is nearer to the opening of ovule will become egg cell. The researchers had carried out a trial to test this hypothesis where they purposely shifted the position of one nucleus nearer to end of embryo sac of plant Arabidopsis. And the result was; instead of one, two egg cells were produced.

Furthermore, they found out that this hormone auxin is produced within the embryo sac itself. This discovery may help in enhancing the fertility of crop plants where greater number of eggs could be developed into mature plants.

This article was published on June 4, 2009.
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By Zaira Hidayah Mohd Arshad 42102119