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Peas in a Pod

Hard-working pods make fat peas

March 17 is the day many gardeners plant peas. So it’s time to know a little about them.
    Did you know that the green pea pod generates most of the energy needed to swell the peas in the pod? It would seem that the leaves on the vine would be contributing. However, research shows that only the leaves immediately adjacent to the pod contribute to the formation of the flowers and the pod itself. Once the pea pod has formed, it generates the energy that causes the peas within to expand. 
    This discovery was made after a researcher wrapped up a newly formed pea pod. At that stage of growth, the pod was flat. Covered with opaque tape, the pods did not produce peas. Covering one-half of the pod produced small peas. Different colored opaque materials gave similar results.
    To study the energy source that produced the pod, he removed one, two or three leaves above and below the flower on the vine. Removing leaves adjacent to the flower reduced the size of the pod. Removing leaves from the vine above the flower had no effect. Removing two of the leaves below the flower had the greatest effect on reducing the size of the pod. Removing the third leaf below the flower had little effect. Thus, the leaves closest to and below the flower had the greatest effect on the growth of the pea pod.
    This is more than an idle-hands study. It proves the importance of proper spacing of seeds and of growing peas where they will receive maximum sunlight. If you use too many seeds, the plants will be crowded, causing more vine and fewer pods and peas because both the pods and the adjacent leaves will most likely be shaded.
    Peaches, plums and apples have similar leaf and fruit association. Only the leaves adjacent to the fruit generate the energy to cause the fruit to grow and sweeten. All of the other leaves on the tree provide energy for the tree to grow new leaves and branches. This is another good reason for pruning because pruning allows the sun to penetrate to the regions of the tree where fruit is growing.
    The knowledge gained from such studies has resulted in the development of new pruning and training practices. If you visit a newly planted orchard, you will see apple, plum and peach trees being trained on trellises to minimize the growth of the tree and to maximize fruit production. 
    This knowledge has helped us understand partitioning. Partitioning means that plants have evolved systems for diverting energy for specific purposes. Most of the leaves on pea vines and fruit trees are designated to grow the plant. Only those leaves nearest the flower and fruit produce the energy to grow the fruit. In the case of the pea, the photosynthesis of the pod produces the energy to grow the peas within.


Ask Dr. Gouin your questions at DR.FRGouin@gmail.com. Please include your name and address.