Biology 2601A/B Lecture Notes - Lecture 18: Depletion Region, Boron, Potential Gradient
1 Dec 2013
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Lecture 18 water and nutrient absorption 2: root structure and function. A plant can"t complete its life cycle in the absence of that element. The element is part of an essential molecule or constituent. Essential elements required by most plants hydrogen, carbon, oxygen, micronutrients such as chlorine, iron, boron, sodium, zinc, etc. But for a non-essential nutrient, it is different: no deficiency zone, however, toxic effects are still possible from elements that are non-essential nutrients. Mobile nutrients can be re-translocated in the phloem. Deficiency symptoms occur in old tissues first, as nutrients are supplied to new growth. Examples nitrogen, potassium, magnesium, chlorine, sodium, etc. Deficiency symptoms occur in new tissues first. Examples calcium, sulfur, iron, boron, copper. Nutrients must be in solution in the soil. Nutrients reach roots via diffusion and bulk flow. As roots absorb nutrients, the concentration near the root drops this drives diffusion of nutrients to the depleted zone.
