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Where do you see the "ray" (Yo) of a petal? Please see the figure. Let's name other parts, too.


Some spots appeared on a petal after a rain. What happened?
They are probably discolored spots from acid rain. Acid rain is composed of raindrops containing dissolved sulfuric acid gas produced by exhaust gases and other pollutants. If it becomes very severe, acid rain kills plants and dissolves buildings and sculptures made of marble. Such damage is reported to occur in Germany and Italy. Using morning glory flowers, some groups are investigating acid rain throughout Japan. In addition to rain, photochemical smog can damage morning glory leaves. In particular, white bleached spots on a leaf surface are produced by ozone. The damaged plants often die. Thus, many plants, including the morning glory, are affected by environmental pollution in the same way as human beings are affected.


(above) You can see a few spots on a flower produced by an early morning rainfall in July 1990 in the city of Kawasaki.
(right) This is an example observed in the city of Takatsuki in July 1990. You can easily see some spots of pink or white.

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