The Relationship Between Plants and Water

The Relationship between Plants and Water Water is an important component for plants. In the body In plants, water functions as a solvent and is also the main constituent of the plant body such as cytoplasm. The amount of water contained in the plant body depends on the type of plant, for example herbaceous plants contain more water than shrubs. The water contained in the entire plant body ranges from 5-95%. The water content for each part of the plant body also varies, such as in grains it is 5-10%, and in plant leaves it is around 50-95%. The water needed by plants is absorbed from the environment through root. This water is then carried by the xylem tissue to be used for plant needs. Roots and water absorption. Roots have certain parts which are absorption areas. Water from the soil enters the root xylem through two pathways. If water enters through the cell walls or spaces between cells, it is said to take the apoplast route. Apoplast is defined as the “dead” part of a plant. This path is taken from the epidermis tissue to the cortex. In the inner part of the cortex there is endodermis tissue which has Caspary bands which are impermeable to water on its walls, so water must enter through the plasma membrane. Then, through the plasmodesmata, water enters the vascular tissue cells. This pathway is called symplast. The symplast includes the cytoplasm of all cells that are connected via plasmodesmata. Xylem itself is part of the apoplast. Water flow in xylem. Capillary force or capillarity is the interaction between the tangent surface of a liquid material and a solid material, so that the surface of the liquid changes shape from flat to slightly wrinkled (meniscus). Capillarity causes liquid to rise into a narrow tube, due to adhesion and cohesion forces. But capillarity is only able to raise water less than half a meter. The presence of capillary forces causes water to move in the xylem. Cohesion mechanisms.A theory was formulated to explain the rise of fluids to the tops of tall trees, namely the cohesion theory. There are three elements in cohesion theory: driving force, hydration (adhesion), and water cohesion. The driving force is the water potential gradient, which progressively decreases from the soil, through plants, to the atmosphere. At a temperature of 20oC, atmospheric RH 100%, Ψ = 0; when RH = 98%, Ψ = -2.72 MPa; at RH = 90%, Ψ = - 14.2 MPa. So a large enough water potential barrier between the soil, through the plants, and the atmosphere is easily obtained, which is enough to raise the water column as high as a tall tree. Experiment a. Measurement of Plant Tissue Water Content Objective: Measuring the water content in plant parts Materials and tools: Plant Materials : Leaves and twigs of the plant whose water content will be measured Tools : Cardboard box, scales and oven Ways of working: 1. The fresh ingredients are weighed at 10 grams and three samples are made. 2. Each sample is stored in a cardboard box and then heated in an oven at 80o C. Heating is carried out until the weight is constant. 3. The weight lost from the heated material is the weight of the water contained in the material. 4. Calculate the water content of the plant using the following formula: BB – BK = % of Wet Weight (BW)/BB Or BB – BK = % of Dry Weight (BK) Experiment b. Measurement of Relative Turgidity of Plant Tissues Objective: Measuring relative turgidity and water deficit of plant tissue Materials and tools: Material : 14 day old plant sprout leaves, Aquadest Tools : Cork borer, scales, petridish, filter paper Ways of working: 1. Make 10 leaf cuttings using a Cork Borer from plants whose soil is at room capacity and another 10 pieces from plants whose soil is slightly dry (not watered for several days). 2. Weigh each piece of leaf and record how much it weighs. This weight is called Fresh Weight (BS). 3. The leaf pieces are then put into a Petri Dish and filled with Aquadest. The Petri Dish was closed and placed in a room with fluorescent lighting with an intensity of + 25 lumens / sq-ft for 3 hours. 4. After 3 hours the leaf pieces were taken, the excess water attached was removed by briefly placing the leaf pieces on filter paper, then the weight of the leaves was weighed. This leaf weight is the weight of the leaf in the turgid state (BT). 5. Next, the cut leaves are dried in the oven at a temperature of 80oC until dry, then the dry weight (BK) was weighed. 6. Calculate the relative turgidity (TR) of the leaves: TR = BS – BK/BT – BK = x100% 7. Calculate the size of the Water Deficit (WD) of the leaves: WD = BT – BS/BT- BK = x 100%