Presentation is loading. Please wait.

Presentation is loading. Please wait.

Transport in Vascular Plants. Transport in Plants Overview  movement of materials from one part of a plant to another  involves 2 specialized tissues:

Similar presentations


Presentation on theme: "Transport in Vascular Plants. Transport in Plants Overview  movement of materials from one part of a plant to another  involves 2 specialized tissues:"— Presentation transcript:

1 Transport in Vascular Plants

2 Transport in Plants Overview  movement of materials from one part of a plant to another  involves 2 specialized tissues: 1. Xylem 2. Phloem

3 Xylem Tissue Structure:  made of thick cell walls  most cells are dead  cells are stacked up on top of another to form a hollow tube through the plant Function:  provides structural support to the plant  carries water and minerals from roots to leaves

4 Phloem Tissue Structure  cells are living  cell walls are porous, allowing exchange of materials with neighbouring cells Function  carries nutrients (sugars and hormones) throughout the plant

5 Water Transport in Xylem (1 of 2) http://www.youtube.com/watch?v=w6f2BiFiXiM&feature=related  Roots take in water through the root hairs & epidermal cells by osmosis  Water flows through the cell walls, into the intercellular spaces within the root, and enter the xylem  Water is then transported in the xylem tissue up through the root into the stem  Within the stem, water and minerals move by diffusion (and, to a lesser extent, active transport) into the other tissues of the plant

6 Water Transport in Xylem (2 of 2)  As the xylem tissue carrying water and other minerals enters the leaf, the conducting vessels branch and rebranch into the numerous veins visible in the leaf  From the end of each vein, water and minerals can diffuse into the cells of the leaf  About 99% of the water that reaches the leaf is lost through transpiration water vaporizes from the leaf through the stomata  this draws (pulls) water up the rest of the plant

7 How does a plant move water up from its roots to its leaves?  3 main theories that have been developed to account for the movement of water in plants  these mechanisms are not mutually exclusive; any or all of these may be at work in a single plant at any one time 1. Root pressure: because of a concentration gradient through osmosis, water enters the root 2. Capillary action: water is drawn into the tiny diameter of the root 3. Cohesion-tension: water likes to stick together and travels up the xylem

8 1. Root Pressure  Plant roots build up pressure that forces water upward  Occurs normally in shorter plants Pressure built in roots of tall trees won’t really push the water that far up

9 2. Capillary Action  takes place because of the adhesion of water molecules and walls of xylem turn upwards  the finer the capillary or vessel, the higher water will climb up

10 3. Cohesion-tension  Also known as “transpiration pull”  http://www.youtube.com/watch?v=At1BJJDcXhk &feature=related  transpiration is the evaporation of water vapour from the leaves through the stomata  depends on the cohesive forces between water molecules and adhesive forces between water and the walls of the vessel

11 Mineral Transport  By testing the concentration of minerals in the roots, scientists know that the amount exceeds that of diffusion  Thus roots are actively pumping minerals and ions from the surroundings  These minerals are dissolved in the water in the xylem or roots, which makes it more concentrated This increases the uptake of water into the plant

12 Translocation: Transport in Phloem  Scientists still unsure of how exactly transport happens in phloem  Phloem transport is bi- directional  Most accepted theory: mass-flow theory Moves from a sugar source a place where sugar is produced by photosynthesis or by the breakdown of sugars) to a sugar sink (an organ which consumes or stores sugar) “borrows” water from xylem to help transport sugars

13 Transport in Xylem vs. Phloem


Download ppt "Transport in Vascular Plants. Transport in Plants Overview  movement of materials from one part of a plant to another  involves 2 specialized tissues:"

Similar presentations


Ads by Google