Translocation and Transpiration Horticulture Plant processes

1. What is the role of water in plants? It is a necessary constituent of all living plant cells and tissues. It serves as a medium for dissolved nutrients and minerals from the soil and takes them to production or storage to sites where they will be used. In plants, water is a needed to carry out many metabolic processes, including photosynthesis. water acts as a coolant and temperature buffer.

Types of WATER FOR PLANTS Moisture for plant growth is stored in the soil. An average of about 500 pounds of water is required to produce one pound of dry plant material. About 5 pounds, or 1 %, of this water becomes an part of the plant. The remainder, the other 495 lbs, is lost through the stomata of the leaves in the course of transpiration.

Types of water Capillary water is used by the plants. This water moves freely in the soil and can move up and down, or horizontally. Forms of soil water not available to plants include gravity water, which is lost to drainage, hygroscopic water that bonds to the soil particles

Translocation Water moves through the plant by translocation and transpiration. Water moves through the Xylem and Phloem Roots have no other means to nourish themselves, and would die without translocated sugars manufactured in the leaves.

Translocation translocated water adds turgor or stiffness to the cells. This pressure helps to provide support to leaves and new tissue. Translocated water also enables a plant to: Maintain temp to carry on most chemical reactions, to maintain the volume of the cytoplasm

Transpiration Transpiration is the evaporation of water from leaf and plant surfaces. It is the last step in a continuous water pathway that starts from the soil and ends in the atmosphere.

Respiration and Transpiration produce heat Transpiration cools the plant. About 90% of all water that enters the plants from the roots is given off during transpiration. The other 10% becomes involved in chemical processes or is tied up in the plant's structure.

Stomata The lower surface of the leaf is dotted with special pore-like structures called "stomata." “Guard cells” Open during the day to permit gas and water vapor exchange with the atmosphere. Close at night or when the plant is under stress.

Stomata Water loss is directly proportional to the surface area exposed to air. Most of the surface area of a growing plant is leaf area. Desert plants frequently have very small leaves or even thorns in place of leaves. They may also have fleshy stems that store water. Fleshy stems and thorns, or very small leaves, are adaptations that help plants survive in hot, dry climates.

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Wilt Water is taken up by root hairs When they lose water more rapidly than they take it up, they wilt. When this occurs, life processes slow and growth may even stop. If a plant remains wilted for too long, it will be damaged and may die. include yellowing, leaf drop and stunting. These usually result in yield loss and less profit for the producer.

Water stress Water stress is more important to plants at certain times. Germinating seed can be killed very quickly by lack of water. Lack of water will also cause many plants to drop flower buds, flowers or even small fruit. Pollen may not develop fully if plants lack water. Corn, for example, may have many missing grains on the ears if adequate water is not available during pollination.

Indications of water stress Show before permanent damage is done Leaves develop a greenish blue tint and may wilt or roll (corn). Pumpkins and other plants with large leaves often wilt during the day and recover at night. When they remain wilted overnight, they need water immediately to prevent yield reduction.

Too much moisture can be just as bad as too little moisture. seeds and plants also require oxygen and carbon dioxide to germinate and grow. Seeds and the roots of plants in waterlogged soil may not receive the gases they need to maintain life processes. Roots die, diseases set in, and both roots and seed may rot. Plants yellow and become stunted. Even large trees can be killed by having their roots covered by water for too long.

EVAPOTRANSPIRATION Evapotranspiration (ET) is the total amount of water removed from soils by evaporation and plant transpiration. Soil evaporation is a direct pathway for water to move from soil to the atmosphere as water vapor. Over the course of an irrigation season, soil evaporation is 20% to 30% of total ET. Soil evaporation rates are highest after irrigation or rainfall.

ET Evapotranspiration can be affected by the weather, the crop type, the crop growth stage, the crop variety, the crop population, surface cover and tillage, the availability of soil water.

Factors affecting Weather factors that have a major impact on this evaporative power include: air temperature, humidity, solar radiation wind. Different crops use different amounts of water over the course of the growing season. corn in the Midwest requires 23 to 28 inches of water in a season; winter wheat requires 16 to 18 inches; while alfalfa requires 31 to 36 inches.

Demonstrate the amount of water in various fresh plants . Demonstrate the amount of water in various fresh plants. Collect samples of fresh plants or plant parts. Keep them in a plastic bag until they can be weighed. Weigh about 100 grams of a sample and then dry it in an oven at 100 F, or use a microwave to dry the samples. Weigh the dry samples and determine the amount of water in the plants and report your results.