Plants require six essential nutrients for healthy growth: nitrogen, phosphorus, potassium, magnesium, calcium, and water. Nitrogen is important for photosynthesis and producing proteins. Phosphorus is essential for DNA, RNA, cell membranes and protein synthesis. Potassium aids in protein synthesis, growth, disease resistance and seed quality. Magnesium is part of the chlorophyll molecule. Calcium develops healthy cell walls. Deficiencies in these nutrients can cause yellow or stunted growth, grey or red leaves, or brown dying leaves.