How Do Plants Get the Nutrients & Water They Need for Growth?
Just as humans digest food for energy, plants use a number of absorption techniques to get the nutrients and moisture necessary for vigorous growth. As roots dive into the soil, they encounter air, water and nutrient reserves. In contrast, photosynthesizing leaves discover sunlight and air as they rise into the sky. Although roots cannot absorb nutrients directly through their extensions, water becomes the carrier for soluble elements and healthy plant growth.
Air and Sunlight
During photosynthesis, plants absorb sunlight using chlorophyll. This sunlight becomes sugar through cellular activities — your plants use the sugars to grow tall and produce nectar during flowering. As plants transpire, or exchange gasses, with the surrounding atmosphere, they gain critical carbon dioxide that is eventually expelled as oxygen. Tiny leaf pores, called stomata, allow gasses to move in and out of the plant for nutrient absorption and exchange. Although plant leaves do not gain a lot of different nutrients from sunlight and gas absorption, both carbon dioxide and sugar production are essential to plant success.
Soil Nutrient Retention
Over a dozen nutrients, from nitrogen to iron, are available in the soil that plants must absorb to continually grow strong. The key to absorbing these nutrients is a soil environment rich in organic material, like compost. Because compost has a negative charge down at the molecular level, it attracts the positively charged nutrients moving within the soil. As a result, nutrients cling to organic matter as roots grow nearby. Roots encountering the nutrients have a chance to absorb the elements. In contrast, poorly managed soils are often nutrient-deficient since natural water movement flushes the elements from the soil — they cannot cling to the limited organic matter for root absorption.
Root Hairs and Micro-Organism Activity
Roots are not simply smooth, long structures. In fact, they typically have tiny hairs that cover most of the roots’ length. These hairs absorb water and soluble nutrients for plant success. However, some critical nutrients, like phosphorus, are not readily absorbed by plant root hairs. Soil micro-organisms, such as earthworms, consume the surrounding elements and expel castings rich in soluble elements. For example, earthworm digestive fluids convert phosphorus to phosphate, an easily absorbed nutrient for plant growth. Between micro-organism activity and root spread, your soil remains friable for optimum water and nutrient absorption.
The acidity and alkalinity levels in the soil, referred to as pH, dictate which elements are available to hungry plant roots. In general, most plants prefer a slightly acidic pH range of 6 to 6.5 — a well-maintained garden with ample organic matter is often the perfect plant habitat. If your pH is highly alkaline, the roots cannot absorb specific micronutrients, like chloride or copper. In contrast, macronutrients, such as potassium, become difficult to absorb with highly acidic soils.