Put simply, plant stems thicken with growth. It's a natural element of the universal growth process. Plant hormones (also called plant growth regulators or simply PGRs) refer to internally-secreted chemicals present in plants ultimately used so as to regulate the plants' growth.
A related term is etiolation. It in effect refers to plant response to stimuli. It is observed that plant seeds grown under insufficient lighting conditions, yield seedlings with typical long, weak stems along with smaller and fewer leaves. This is essentially owing to a dearth of chlorophyll. Also, the plant's height is explained as enabling it to reach out for any possible source of light sooner.
On the other hand, on subsequent exposure to normal light, you find stem growth rate diminished, the stems actually thicken, while leaves expand and become green. This particular process is called de-etiolation.
A related term is etiolation. It in effect refers to plant response to stimuli. It is observed that plant seeds grown under insufficient lighting conditions, yield seedlings with typical long, weak stems along with smaller and fewer leaves. This is essentially owing to a dearth of chlorophyll. Also, the plant's height is explained as enabling it to reach out for any possible source of light sooner.
On the other hand, on subsequent exposure to normal light, you find stem growth rate diminished, the stems actually thicken, while leaves expand and become green. This particular process is called de-etiolation.
