Pilchuck Pollinator

After germination, the roots and shoots grow in response to the effect of gravity with the aid of auxin.  Roots are, by nature, positively geotropic, that is they grow in the direction of gravity. Stems, however, are negatively geotropic, growing opposite to gravity. The growing tip of a root and stem, known as the apical meristem is where the auxin is produced in minute, but sufficient quantities. One of the mysteries of growth is the ability of the auxin to redistribute in its concentration. The auxin flows back from the meristem into the elongating part of the new shoot.

Larger seeds, such as corn, quickly develop a separate root and stem. However, the small rhododendron seed develops a single shoot, which is the beginning of the root and stem.  In my observation, the root formation is the first priority. If this is true in a germinating seed which is lying on its side when the shoot starts to develop, gravity causes auxin in the upper part of the shoot to stimulate the cells to grow more rapidly than those across the bottom. This is the physiological means for the shoot to bend and grow down into the growing medium (due to the effect of gravity - hence, positively geotropic.) The opposite end, which will form the stem, then begins a slow vertical growth.

I believe that in this initial phase of development, the stem end straightens any initial bend due to natural auxin migration. However, it is interesting to note, that once the bending occurs in larger plants, and growth continues, the only response to changing orientation of the plant will occur in the area of the newly forming part of the stem. As an example, if a growing plant is laid on its side, only the new growing part of the stem will bend upwards for the reasons described above.

Lastly, purely for reference, a plant (which is placed on a window sill) bends to face the light because of another of nature’s factors known as phototropism. This phenomenon is also controlled by our friend auxin. In this case, auxin is redistributed to the shady part of the stem, causing that side to grow at a faster rate. This is most common in sun-loving species. Most shade-loving species display little or no phototropic responses (important in their selection as house plants.)

My reference books point out that plant physiologists are still at a loss to explain all the complex biochemistry of cell growth, the migration of auxin, etc. This brings to my mind the poem TREES, by Joyce Kilmer, which concludes that "poems are made by fools like me, but only God can make a tree."

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From our Treasurer:  It is time to start thinking about our Fall season just a few weeks away.  One of the important items at the beginning of our year is dues. The dues for the 2006-07 season remain at $35 for an Individual membership and $40 for Family membership. You will find a dues envelope in your Pilchuck Pollinator Newsletter, unless your dues are paid in full for this season.  If there’s any questions please contact Wayne Lawson at our first meeting on September 7^th.  The chapter keeps $8 from each dues payment and the rest goes to National.  This pays for, amongst other things, the Quarterly magazine you receive with your paid up dues.  The deadline for timely payment to receive your Quarterly is December 7^th.