How nutrients move
Photosynthesis produces sugars in the leaves. These are transported throughout the plant and especially to the:
- Growing shoot tips
- Growing root tips
The transport medium is the sap – the phloem and xylem. Phloem contains up to 17% solids as sugars. It moves sugars from the leaves to the growing tips, roots and fruit. Xylem is 99.9% pure water with traces of minerals. It moves water and minerals from the roots up into the leaves.
Calcium (Ca), boron (B) and manganese (Mn) are necessary elements for plant growth and they are not transported in ionic form by the phloem (although they may be transported in chelated form by the phloem). It is best to have these elements delivered by the xylem, which means they need to be available for the soil biology to deliver to the plant.
Temperature affects the transport of sugars in certain plants. About 85% of plant species are C3 plants. They include the cereal grains: wheat, rice, barley, oats. Peanuts, cotton, sugar beets, tobacco, spinach, soybeans, and most trees are C3 plants. Most lawn grasses such as rye and fescue are C3 plants. At temperatures above 76° F. these plants use water less efficiently, respiring it out of the leaves. Photosynthesis declines and so does availability of Ca, B and Mn to the new leaves. In hot weather, C3 plants can develop a deficiency of these elements. They need higher available levels of these elements in the soil to counteract this effect. Well grown, glossy leaved plants tend to reflect more sunlight and keep the plants cooler too.
C4 plants do not have these temperature limitations. They evolved in drier, hotter, climates and use water more efficiently. They do not lose energy and carbon due to photorespiration and have an additional CO2 fixing mechanism. The drawback is that they are not as well suited to light-poor situations as the C3 plants.
Rice, Wheat, Rye, Oats
(all squash family)
(all nightshade family)
All woody trees