The mechanism through which plants absorb water and nutrients from the soil is called osmosis and active transport. Osmosis refers to the movement of water across a semipermeable membrane from an area of lower solute concentration to one of higher concentration. Active transport includes the uptake of essential nutrients like minerals against their concentration gradient, requiring energy. This process is vital for plant health, ensuring they have enough water for photosynthesis and minerals for growth, thus maintaining overall ecosystem productivity.