This solution then flows towards the sugar sink, where the pressure is relieved by removing the sucrose and water. Most of these are acquired from the soil. Macronutrients are required in large amounts and are usually building blocks of organic molecules. Micronutrients are typically used as enzyme cofactors and are required in small amounts. Be able to identify an element as either a micro- or macronutrient.
Plants regulate their own soil pH to release required minerals.
Nitrogen cycling Most of this chapter focuses on nitrogen cycling in the soil. The reason for this emphasis is that nitrogen availability is most often the factor limiting plant growth. Fig 37.8 is a good figure to study. The main sources of these is nitrogen fixing bacteria and the decomposition of organic material by microbes. Ammonia picks up a proton from the soil to form ammonium.