The Ripening Signal: Ethylene Hormone Explained

If ethylene concentration increases in a climacteric fruit, then enzymes that break down starch into sugar are activated. If starch becomes sugar, then the fruit ripens.

If all the fruit on a tree ripens at once, then it attracts a larger group of animals to eat the fruit and spread the seeds. If synchronization increases the chance of successful reproduction, then it is an evolutionary advantage.

If ripe apples are climacteric and constantly emitting ethylene gas, then that gas will fill the surrounding air. If flowers are sensitive to ethylene, then they will respond by rapidly aging and wilting.

If silver ions (Ag+) interfere with the ability of ethylene to bind to its receptor, then the signal for wilting is never received. If the signal is never received, then the flowers stay fresh for a longer time.

If a plant is chewed on and releases ethylene gas, then neighboring plants can detect that gas. If they detect it, then they may begin producing defensive chemicals before they are even attacked.

If auxin levels are high, they inhibit the effects of ethylene. If the auxin supply from the leaf blade stops, then the leaf becomes sensitive to ethylene, leading to the breakdown of the abscission zone.

If the molecule is a simple alkene with a double bond between two carbon atoms, then its chemical formula must be C2H4.

If CO2 acts as a competitive inhibitor for ethylene receptors, then high levels of CO2 will block the ripening signal. If the signal is blocked, then the fruit can be stored for longer periods without spoiling.

If ethylene is a gas, then it can escape the skin of one fruit and travel through the air. If nearby fruits absorb this gas, then they will receive the chemical signal to begin their own ripening process.

If the level of auxin in a leaf drops and the level of ethylene rises, then a specialized "abscission layer" at the base of the petiole weakens. If this layer breaks, then the leaf falls from the tree.

If a hormone is composed of a simple two-carbon hydrocarbon chain that lacks polar groups, then it remains in a gaseous state. If it is a gas, then it can easily diffuse through the air.

If a plant needs to recycle nutrients from an old flower or leaf, then it must initiate a controlled death of those cells. If ethylene triggers this breakdown, then it is driving the process of senescence.

If the presence of ethylene causes a fruit to produce even more ethylene, then the signal is being amplified. If an initial signal leads to an increase in that same signal, then the system is following a positive feedback loop.

If a seedling encounters a rock, then it produces ethylene to change its growth pattern. If this pattern involves slowing elongation, thickening the stem, and growing horizontally, then it is known as the triple response.

If the vertical path is blocked, then the seedling must find a new route. If ethylene is produced due to the pressure, then it reorients the cell growth to move the plant sideways.

If a plant experiences physical or environmental stress, then it produces "stress ethylene" to trigger protective responses. Wounding, water stress, and infection are all known triggers for this production.

If a fruit responds to an increase in ethylene by ripening and producing even more ethylene, then it is climacteric. While bananas, apples, and tomatoes do this, grapes and strawberries do not ripen further once picked.

If bananas are shipped green to prevent bruising, then they must be forced to ripen at the destination. If the shippers pump ethylene gas into a sealed chamber, then they are using a ripening room.

If ethylene is a gas that can pass through cell membranes, then it doesn't need a pump. If it binds to specific proteins in the ER and disables a negative regulator, then the ripening genes can be expressed.

If scientists track the "building blocks" of ethylene in the Yang Cycle, then they find that the process always starts with this specific sulfur-containing amino acid.