Plant nutrition plants obtain sunlight and usable chemical elements from the environment.

Four factors are necessary for plant growth There are thirteen different minerals that plants require for proper survival and growth. Six of these essential nutrients are required in large amounts. These are: nitrogen, phosphorus, magnesium, potassium, sulfur, calcium. Plants need sunlight, water, and air to thrive. But that’s not enough. Without a nutritious diet, plants will get sick, wither, and even die if they don’t have adequate nutrition. Plants generally require four things for proper nutrition. For a plant to grow, it must build new cells, which are then assembled into new tissues. These new cells must have cell walls, DNA, mitochondria, and all the other cell components. Aside from the carbon and oxygen obtained from CO2 in the air and hydrogen from water, plants must get all of these raw materials elsewhere, usually from the soil. In all, there are 13 different minerals (each of which is an element) that plants require for proper survival and growth.

Hydroponically Grown Plants These plants are grown without soil. Instead, they are grown in water that has chemicals added. By adding or withholding exact amounts of certain chemicals, it is possible to determine which are essential and in what amounts. These findings are important in helping farmers determine what types of fertilizers they need for crops, as the farmers try to coax more growth out of each acre of land than would occur naturally.

Without enough nutrients, plants are stunted, spotted, or otherwise abnormal Healthy control N-Deficiency P-Deficiency K-Deficiency

Nutrients and typical lawn fertilizers: Follow “N-P-K” rating N: Nitrogen P: phosphorus K: Potassium

Mycorrhizae Fungi living around and within the roots increase absorptive surface area. In exchange for providing increased vitamins and minerals to the plant, the fungus receives sugars, amino acids, and vitamins in return. Most plants have fungi growing all around and even within their roots, forming mutualistic associations known as mycorrhizae.

Nitrogen Fixation Nitrogen gas in the air must be converted to nitrate or ammonium in soil by bacteria for it to be used by plants. This is called nitrogen fixation. A mutually beneficial relationship has evolved that enables plants to gain access to the nitrogen fixed by these bacteria.

How do bacteria and plants form this mutualistic alliance? The alliance between plants and nitrogen-fixing bacteria develops in a few simple steps.

Some Plants Have Alternative Ways of Obtaining Nitrogen These plants ingest animals, such as insects, to obtain nitrogen they do not get in the soil, and are called carnivorous (insectivorous) plants. One example is the Venus flytrap. Not all soil conditions are conducive to the growth of nitrogen-fixing bacteria, and some plants have alternative ways to acquire nitrogen. Insect-eating (insectivorous) plants, for example, generally grow in very acidic soils in which nitrogen-fixing bacteria do not thrive.

How is water moved through a plant? In the cohesion-tension mechanism, the plant does not need to expend any energy to pump water and minerals up from the roots to the leaves. As water evaporates from the leaf surface, tension is created, and water is pulled up from the roots, due to the cohesiveness of water molecules with hydrogen bonds.

Sugar Movement Through the Plant is by pressure flow (bulk flow) Phloem controls sugar movement throughout the plant in five steps: Figure 17-36 The pressure-flow mechanism of fluid movement in the phloem. Sugar is produced in the leaves (the “source”) and transported to places (“sinks”) where sugars are needed.

Organisms Besides the Plant Benefit from the Sugary Phloem Aphids pierce the plant stem to gain access to the sugary phloem. Figure 17-37 Drinking from a fire hose on a small scale. The sugary fluid in the phloem is under such high pressure that aphids drinking it can’t always consume it all, and some is forced through their digestive system and out of their anus (at which point, ants may consume the fluid).