Homeostasis literally means _same state_, the desired state for a healthy plant. And plant health depends upon availability of water, air, light and nutrients, all of which function within the plant cells. Plant cells have rigid walls that contain organs that regulate plant health and growth. Among the plant cell organs are the vacuoles, the largest and main mechanisms for maintaining homeostasis, and chloroplasts, which produce energy.
Vacuoles Regulate Turgidity
Plant cells contain one or more vacuoles, which vary widely in form, size, content and functional dynamics, according to Francis Marty in "Plant Vacuoles," published by American Society of Plant Physiologists. However, the central vacuole is the largest cell organ and is responsible for cell turgidity. When a plant receives optimal moisture, vacuoles fill with water and exert hydrostatic pressure against cell walls, preventing wilting.
Overwatering Kills Plants
Although plants can wilt or die from drought, overwatering also kills plants. Under proper conditions, roots absorb both water and oxygen. However, waterlogged roots cannot absorb oxygen, disrupting homeostasis and causing roots to die. Waterlogging occurs in heavy, compacted soils that do not allow for air spaces between soil particles, as well as from too much rainfall or irrigation.
Saline and Nutrient Levels Affect Homeostasis
Nutrients provide ions that interact within plant cells to create osmotic pressure that pulls water into vacuoles and keeps a plant from wilting. For this reason, plants require both macro- and micronutrients. Organic matter provides both types of nutrients, as well as properties that improve soil quality. Chemical fertilizers also provide nitrogen, phosphorous and potash, the major nutrients needed for plant health and growth. Some formulations also provide minor nutrients or trace elements that benefit plants.
Soil, water and fertilizers contain salt in various quantities. Although plants can tolerate a small amount of salt, excessive salt levels are toxic. Too much salt in soil interrupts homeostasis by preventing plant roots from taking in water, resulting in slow growth, wilting or even death of the plant.
Potted plants are particularly susceptible to salt buildup from the use of hard water or when chemical fertilizers are used in irrigation water. To avoid this problem, water thoroughly with clear, soft water, such as distilled water or rain water, once a month.
Treat salt buildup in your garden in a similar way, watering thoroughly with fresh water. If necessary, dig temporary trenches to provide adequate drainage during this salt-leaching treatment to avoid waterlogging plants.
Chloroplasts Provide Energy for Health and Growth
Plants get their energy from the sun. Chloroplasts within plant cells convert energy from the sun into sugars, which fuel plant health and growth. Plants vary regarding their light requirements, but insufficient light interferes with homeostasis, resulting in loss of plant vigor, irregular growth or even plant death. Symptoms of insufficient light include light-colored or yellowing leaves; small leaves; stunted or elongated, spindly growth. Check with garden experts or guides to learn the optimal light requirements for individual plant species.