Reaching New Heights: Gibberellins Function

If gibberellins stimulate the cells in the internodes to stretch and multiply, then the result is a significantly taller plant stem.

If a seed absorbs water and releases gibberellins, then those hormones signal the breakdown of stored food to start growth; therefore, they are essential for germination.

If ethylene is a gas used to ripen fruit after harvest, and gibberellins are internal chemicals that wake up a seed, then they serve different stages of the plant life cycle.

If gibberellins affect growth and energy release, then they result in larger fruits, rapid stem elongation, and seed activation; however, leaf drop is caused by ethylene and abscisic acid.

If environmental cues trigger a massive surge of gibberellins in the stem, then the plant will rapidly elongate its stalk to produce flowers and seeds.

If the embryo needs energy to grow, then it must digest the starch in the endosperm. If gibberellins trigger alpha-amylase, then that enzyme converts the starch into usable glucose.

If ethylene's chemical structure allows it to exist as a vapor that travels through the air, then it is a gas; since gibberellins travel through the plant's vascular tissue, they are not gases.

If gibberellins increase the length of the fruit stalks (pedicels), then the grapes have more room to expand. If they have more room, then the individual grapes grow larger and the cluster is less prone to mold.

If gibberellins act as the "accelerator" for growth and ABA acts as the "brake" to keep the seed dormant, then the ratio between them determines when the seed will sprout.

If ethylene triggers senescence (aging) and fruit ripening, and gibberellins trigger elongation and germination, then their roles in plant maturity are functionally opposite.

If growth hormones are needed where the most active development occurs, then the apical buds, roots, and young leaves are the logical primary sites for gibberellin synthesis.

If the G. fujikuroi fungus infects a rice plant and floods it with gibberellins, then the plant grows so tall and thin that it falls over and dies; this discovery led to the identification of the hormone.

If ethylene signals a fruit to drop and rot, and gibberellins delay that aging process, then farmers use gibberellins to extend the harvest season.

If many dwarf plants are short because they lack the genes to produce their own gibberellins, then adding the hormone externally will allow the cells to elongate normally.

If a molecule is a hormone, then it must bind to a receptor and trigger a genetic response. If it works efficiently, then it only requires a tiny amount to travel through the xylem or phloem.

If ethylene is the primary agent of fruit softening and decay, and gibberellins act to maintain tissue firmness, then the two hormones have an antagonistic relationship regarding fruit shelf-life.

If gibberellins are released by the embryo, then they must travel to a nearby tissue. If the aleurone layer responds by secreting amylase, then it is the "responder" tissue in the germination process.

If the seed contains a large supply of starch (the endosperm), then it needs gibberellins to activate the enzymes that turn that starch into sugar for the growing plant.

If a plant is under stress, then it produces ethylene to handle the damage but reduces gibberellins to stop wasting energy on growth. Gibberellins would not be used to speed up growth during a water shortage.

If malting requires barley seeds to sprout so they release enzymes, then adding gibberellins ensures that all the seeds start germinating at the exact same time and speed.