Plants are amazing, especially when you wonder how do plants grow. There are over 350,000 species of plants, above ground and underwater plants. Each one has to survive some harsh conditions to grow, and you can see the tenacity of plants to grow when you see them perched on the side of canyon walls, or pushing their way up through old pavement. Their will to survive and propagate is intense!
Plants include flowers, trees, shrubs, bushes, grass, moss, vines, herbs, seaweed, and green algae. These have much in common. They depend on Nature for survival, and the contents of other living and natural things. They need sunlight (except deep sea plants), water, air, bees and insects, soil, animals, and fire for life. Some pine trees only release their seeds after a big fire; they need the heat to open the cones and seeds.
Some underwater plants get their nutrients from water, surviving without sunlight. In hydroponic growing, plants are grown in just water instead of soil, and you can see the root growth. The water must have the nutrients needed, or the addition of plant food for the plant to thrive.
To answer the question of how do plants grow, you must look at propagation. Some plants have both male and female parts, others do not, but they all depend on wind, air, animals, bees and insects to help with pollination and fertilization. Others will send out runners and tubers, or create corms, bulbs, suckers, and adventitious buds to propagate new plants through the soil to new locations. Humans help with splicing for cross breeding and new growth on old plants.
Plants that have seeds create little packages (seeds) that contain a food store and a baby plant embryo, similar to a fertilized egg, and there is a protective seed coat over the seed. When fertilized through pollination, the seed forms after a flower dies. The flower contains male and/or female parts that create an ovum ready for fertilization. This becomes the seed or fruit containing seeds.
The seed drops to the ground and begins to soften with moisture until the seed coat opens enough for germination to break through with a tap root, root hairs, and the plant top begins to grow towards light and warmth. This is the seedling plant. The roots grow down to find more moisture and the top of the plant grows up to find food and energy.
Plant food comes from the water and soil. Plants take in food and energy through photosynthesis from sunlight, and respiration through their leaves (osmosis). They take in carbon dioxide from the air in the daylight and release oxygen during the night. It is important for plants to obtain the right minerals from soil. Fortunately, Mother Nature works just perfectly in most cases and plants thrive.
When you look at all it takes for Nature to be in perfect balance and answer the question of how do plants grow, it is an amazing thought, and a miraculous process.