transport in plants

 
Root Hair Cells: on the region above the root tip, cells of the outer most layer produce tiny, tube-like hairs called root hairs, these grow between the soil particles and provide a large surface area. 
- they take up water through osmosis.
- they take up mineral ions through active transport.

osmosis: when water molecules move from a region of high water potential to a region of lower water potential through a semi-permeable membrane
active transport: when mineral ions move from a region of lower concentration to a region of higher concentration, against the concentration gradient with the help of energy. 

- As the water enters the cell, its water potential becomes higher than in the cell next to it, e.g. in the cortex. So water moves, by osmosis, into the next cell. Some of water may also just seep through the spaces between the cells, or through the cell walls, never actually entering a cell.

Transpiration:
Transpiration is the evaporation of water
at the surfaces of the mesophyll cells,
followed by loss of water vapors from
plant leaves, through the stomata.

Water in the leaf cells forms a thin layer on their surface. The water
evaporates into the air spaces in the spongy mesophyll. This creates a
high concentration of water molecules. They diffuse out of the leaf into
the surrounding air, through the stomata, by diffusion.

Mechanism of water movement through a plant:

Water molecules are attracted to each other (cohesion) a water vapor
evaporating from a leaf crates a kind of suction, pressure of water at
the top of the vessels is lower than that of the bottom à water move up
the stem in the xylem, more water is drawn into the leaf from the
xylem. This creates a transpiration stream, pulling water up from the roots. Factors affecting Transpiration: Temperature: higher temperature -> higher transpiration (more evaporation) Light intensity: higher light intensity -> higher transpiration (stomatal opening) Humidity: higher humidity -> lower transpiration (more water molecules in the outer environment) Air movement: higher air movement -> higher transpiration (wind removes the water vapor accumulated outside) Translocation: Translocation is the movement of organic food such sucrose and amino acids in phloem; from production units to storage units.

Carbohydrates are transported through a plant in the form of sucrose, glucose, and
proteins as amino acids.
Substances can be transported in any direction in phloem:
from photosynthesizing leaves down to roots for storage.
upwards to growing buds, flowers, leaves and fruits for respiration and growth.
from storage organs such as the root tubers to all parts of the plant.

1. Glucose the product of photosynthesis is very important as it makes many other
important nutrients, e.g. sucrose.
Sucrose in the leaves then enters the phloem vessels.
The phloem transports the sucrose all across the leaf where it can be made used of.

2. Amino acids are also transported in the phloem.
Sucrose and amino acids are transported to every tissue of the
plant, each cell use it in a different way. Root cells convert sucrose into glucose for respiration and store it.
Growing cells make cellulose for cell walls from sucrose and use
the amino acids to make proteins for growth.
And fruits use the sucrose to make the attractive scent and
tasty nectar to attract insects. 

Distribution Of Xylem And Phloem Vessels:

- In the roots, xylem and phloem are in the center to withstand stretching forces. - In the stems, they are arranged in bundles near the edge to resist compression and bending forces. - They are grouped together into veins and vascular bundles as they pass through leaves. 

Xylem Vessels:

Function: Xylem transports water and mineral salts from the roots up to other parts of the plant. Structure of the xylem tissue: Mature xylem consists of elongated dead cells, arranged end to end to form continuous vessels (tubes). Xylem vessels consist of dead cells. They have a thick, strengthened cellulose cell wall with a hollow lumen. The end walls of the cells have disappeared, so a long, open tube is formed. The walls of the xylem vessel contains holes called pits which water enters through. Mature xylem vessels: - contain no cytoplasm - are impermeable to water - have tough walls containing a woody material called lignin Wilting: - a plant relies on its cells to stay turgid in order for it to be rigid. - if the amount of water being lost is more than the amount of water being taken in, the cells become flaccid, causing the plant to wilt. - high transpiration leads to wilting. - when leaves wilt, the stomata closes. test yourself: https://forms.gle/4ZLRcUsQW1eJ93AM6