Plants Flashcards
Give examples of plant organs?
stems, rooted and leaves
What are the 5 tissues in a plant?
- epiderma
- palisade mesophyll
- spongy mesophyll
- xylem and phloem
- meristem
What does the epidermal tissue do?
covers the whole plant
What does the palisade mesophyll tissue do?
part of leaf where most photosynthesis happens
What dies the spongy mesophyll tissue do?
contains big air spaces to allow gases to diffuse in and out of cells
What does the xylem and phloem do?
transport things like water, mineral ion and food around the plant
What is the meristem tissue?
found in growing tips of shoots and roots and is able to differentiate into different types of plant cells allowing the plant to grow
What are the four tissues in a plant?
epidermal, mesophyll, xylem, phloem
structure of a plant from top to bottom?
- waxy cuticle
- epidermal tissue
- palisade mesophyll tissue
- spongy mesophyll
- epidermal tissue
- stomata
How is the epidermal tissue related to its function?
covered with waxy cuticle, reduces water loss by evaporation
How is the upper epidermis related to its function?
transparent so light can pass through to the palisade layer
How is the palisade layer related to its function?
lots of chloroplasts, near the top so can get lots of light
How are the xylem and phloem related to their function?
network of vascular bundles which deliver water and other nutrients to the entire leaf and take away glucose produced in photosynthesis
How are some tissues adapted for efficient gas exchange?
- lower epidermis has stomate which let C02 diffuse directly into the leaf
- air spaces in spongy mesophyll tissue increase rate of diffusion of gases
What do the phloem do?
transport food substances ( mainly dissolved sugars) made in the leaves to the rest of the plant for immediate use or storage
What direction fo the phloem flow?
both directions
What is the process which takes place in the ploem?
translocation
What do the phloem tubes look like?
columns of elongated living cells with small pores in the end walls to allow cell sap to flow through
What do the xylem do?
carry water and mineral ions from the roots to the stem and leaves
What direction of the xylem?
up
What do the xylem look like?
dead cells joined end to end with no end walls between them and a hole down the middle - strengthened with lignin
What is the process which takes place in the xylem?
transpiration stream
What is transpiration?
loss of water from the plant
What is transpiration caused by?
evaporation and diffusion of water from a plants surface
Where does most transpiration happen?
leaves
explain the transpiration stream?
- evaporation creates slight shortage of water in leaf so more water is drawn up from the rest of the plant through the xylem vessels to replace it
- means more water is drawn up from the roots and so there is a constant transpiration stream of water through a plant
What is transpiration a side effect of?
the way leaves are adapted for photosynthesis
What is transpiration rate effected by?
- light intensity
- temperature
- air flow
- humidity
How does light intensity effect transpiration rate?
brighter the light, greater transpiration rate
stomate begin to close as it gets darker
How does temperature effect transpiration rate?
warmer it is, faster transpiration rate
How does airflow effect transpiration rate?
better air flow, greater transpiration rate
If air flow is bad, water vapour sits around leaf and doesnt move around. high concentration of water particles inside and outside leaf so diffusion doesnt happen as quickly. If high air flow, water vapour is swept away maintaining a low concentration of water in air outside leaf and then diffusion happens quickly
How does humidity effect transpiration rate?
- drier the air, faster transpiration
need a high concentration gradient
How can you estimate rate of transpiration?
measuring uptake of water from plant - measuring distance bubble moved
What are guard cells adapted to do?
open and close stomata
What happens when the guard cells have lots of water?
guard cells fill with water and go plump and turgid making the stomata open so gases can be exchanged for photosynthesis
What happens when a plant is short of water?
guard cells loose water and become flaccid making the stomata close helping to stop water vapour from escaping
What are guard cells also sensitive to?
light at night - close to save water
Where do you find most stomata?
undersides of leaves as its cooler and shaded so less water lost
What have guard cells adapted for?
gas exchange and controlling water loss in leaf
