From Seed to Seed:
Plant Science for K-8 Educators
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From Seed to Seed: |
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Digging Deeper It Doesn't Do It All Believe it or not, there are plant growth regulators other than auxin! Gibberellin is a plant growth regulator that stimulates both cell elongation and cell division. There are more than 50 known gibberellins, identified as GA1, GA2, GA3, etc. Even tiny amounts of these substances can cause dramatic changes in growth in plants. Gibberellins affect the length of the stem between nodes (the internodes), and therefore the overall height of the plant. Gibberellins also influence flowering cycles and can cause seeds to break out of dormancy and begin to grow. Commercially, gibberellic acid is most commonly applied to crops of seedless grapes to produce larger fruit. Abscisic acid is another growth regulator, so named because it was once thought to be involved in the process of leaf abscission. It is now known to play a role in inducing dormancy in seeds and buds. Cytokinin is a plant growth regulator that stimulates cell division. Ethylene is produced by ripening fruit, and also acts to hasten ripening in other fruit nearby. So... one bad apple can spoil the whole bunch! Students can experiment with the effects of ethylene by separating unripened tomatoes (or apples) into two batches. In one batch, students can place an overripe tomato. Which batch of tomatoes ripens first?Although we have addressed plant growth regulators individually,
keep in mind that more than one substance may be involved in a certain
growth response. For example, auxin and gibberellin may work in concert
to control stem elongation. And abscisic acid plays a role alongside ethylene
in the fruit-ripening process. Please click the BACK button on your browser to return to the course. |
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