WATER TRANSPORTATION IN PLANTS. Done by : Annabel Diong

A plant body.

Introduction This slideshow presentation will explain in detail about how the xylem in the plant works and how it transports water, how a desert plant absorbs water, the structure of both desert and regular plant, and the xylems significance. It will also contain many images showing what the xylem is and finally how the xylems affects the photosynthesis.

XYLEM IMAGES.

What is a xylem In a vascular plant, the xylem is one of two transportation tissues throughout the plant. The xylem walls are strong and lignin that gives the plants support. The xylem is made out of dead cells, while the phloem is made out of living cells. These vascular tissues are typically long And slender, their form similar to pipes. It is found in a vascular bundle arranged in long and discrete strands, the xylem lies closer to the interior of the stem with phloem towards the exterior of the stem. The xylem is responsible for transporting water and 3 essential minerals (nitrates, phosphates and potassium) obtained from the root hairs (very small and thin and grow mainly at the tips of the roots) throughout the plant internally, and Replacing water loss during transpiration and Photosynthesis. The root hairs provides a large surface area to give good absorption. This form of transportation is vital for theplants survival and for the process of photosynthesis.

The Importance of XYLEMS. The presence of xylem in vascular plants is vital for the plant’s survival and for the process of photosynthesis. Water travels through the xylem vessels from the root hairs of the plant to the leaves where photosynthesis is carried out in order to produce the glucose and provide food for the plant. If water is not conducted via root hairs to every part of the plant, the plant will dry Out and wither, because the water absorbed is what replaced the water lost during transpiration And photosynthesis. When a plant is not well watered, osmosis would not happen ( osmosis is the movement of Water molecules from a region of high water concentration to a region of low water concentration across a partially permeable membrane). The cells would not become turgid, and leaves are entirely supported by turgor pressure. The turgid cells ( cells that have fully absorbed water) would start to inflate and push against the cell walls to the plant tissues. We know this because when a plant is not well watered the leaves would start the droop and wilt, meaning the cells are starting to lose water, thus losing their tugor pressure. Loss of water from cells is also responsible for opening and closing the guard cells. The stomata pores automatically closes when water supply from the roots decrease, the guard cells control and change the shape of the cell, turning it flaccid. When the stomata pores close it prevents further water loss and also stops carbon dioxide from entering resulting in stopping photosynthesis throughout the plant. Young plants which Have little woody tissue rely on tugor for support against wind and gravity. A non- woody plant which Water loses a lot of water has many plasmolysed cells and as a result the plant wilts.

A xylems functions and how it travels. The process of water traveling through a plant is rather discreet. It all starts off with the Outer layer of the root, the epidermis. This area has projections called the root hairs, which Project into the soil increasing surface area for the uptake of water and minerals. Water is then enters the vacuole in the root hairs and into the cortex, which is Then absorbed by the parenchyma cells surrounding the stele (the area containing the phloem and xylem vessels) Through osmosis, because there is higher water concentration in the soil water than in the cell sap. ) once a cell becomes turgid, water is then passed around the parenchyma cells until it reaches the stele ( where the vascular bundles are located), it is then conducted up the xylem vessels from the method root pressure, but root pressure alone is not strong enough to bring water up to the leaves of tall trees, other methods like transpiration pull(. it is a tension of negative pressure from above) and capillary action ( it plays a part in upward movement of water in small plants, but cannot account for water rising up of tall trees.) are at work to help it. Usually 90% of the water that enters the plant is lost during transpiration ( evaporation of water at any part of the plant) and less than 5% is loss through the cuticle. From the xylem vessels, the water is then finally brought to the leaves of the plant, the water is the spread throughout the plant by the leaf veins.

INTERNAL Leaf structure A leaf is often flat in order to absorb the most light, and thin so that the sunlight will shine through it. The internal features of a regular leaf has a lamina and on either sides of the mid-rib has a upper epidermis ( made up of a single layer of closely packed cells, covered on the outside by a cuticle, this cuticle protects the leaf and prevents excessive evaporation of water. That is why desert plants have a much more waxy cuticle, to prevent further loss of water in the harsh climate. The mesophyll lies just below the upper epidermis, this area is mainly where Photosynthesis happens. The palisade tissue (consists of 1 or 2 layers of closely packed, long and cylindrical cells, and these cells contain numerous chloroplasts, which enable them to absorb maximum sunlight for photosynthesis) and the spongy tissue are the two regions of the mesophyll that can be recognized. Below the mesophyll is the lower epidermis, similar to the upper epidermis but contains an opening, the stomata ( a small opening controlled by guard cells to enable the exchanging of gases).

Bibliography. /gif/xylem1.gif phloem _plants.htm