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Why Leaves Change Color - The Physiological Basis
William R. Chaney, Professor of Tree Physiology, Purdue University
 Myths
about Jack Frost are so ingrained in our folklore it is difficult
to separate fact from fantasy when explaining the spectacle of autumn
color. These legends compensated for the lack of knowledge concerning
the natural phenomenon. Today, however, the display of color we
enjoy each fall is explained by understanding plant pigments, the
physiology and anatomy of leaves, and the influence of climate and
seasonal weather conditions.
Leaf Pigments and
Seasonal Changes
Four leaf pigments account
for leaf color and its changes in the autumn; chlorophylls, carotenoids,
tannins, and anthocyanins. Chlorophyll located in tiny organelles
called chloroplasts in the cytoplasm of cells gives leaves and other
plant parts their green color. This pigment absorbs the radiant
energy of the sun and is essential for the process of photosynthesis
in which carbon dioxide and water are transformed to the sugars
necessary for tree growth. Throughout the growing season in a healthy
tree, chlorophyll is continuously being produced and destroyed.
Even though light is necessary for the formation of chlorophyll,
continued exposure of new chlorophyll to sunlight with its damaging
high-energy ultraviolet wavelengths will destroy the pigment. Hence,
if a leaf is to remain green, new chlorophyll must be made constantly.
Full
Story, http://www.extension.purdue.edu/extmedia/FNR/FNR-FAQ-5.html
Saving Seeds from the Garden
B. Rosie Lerner, Consumer Horticulture Extension Specialist
Collecting seeds from
garden plants to plant next year may seem like a good way to save
money, but you may be in for a surprise. Some seeds can be saved
from year to year with good results, particularly the old-fashioned
cultivars. But modern hybrid cultivars rarely breed true from collected
seed.
To get that disease-resistant
tomato or that frilly double petunia, two or more plants that have
desirable characteristics were crossbred. The seed from these hybrid
plants will produce variable results due to recombination of different
genes. Thus, the resulting plants may not be as productive, attractive,
disease-resistant or flavorful. Each seedling could be quite different
from the parent and from each other.
Full
Story, http://www.hort.purdue.edu/ext/savingseeds.html
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