plant tissues,organs and system-biology

• epidermal tissue-covers the whole plant,covered in waxy cuticle to reduce water loss
• palisade mesophyll tissue- where most photosynthesis happens contains lots of chloroplasts and is found in the upper part of the leaf
• spongy mesophyll tissue- contains lots of air spaces and has a thin outer layer
• xylem-transports water and mineral ions from the roots to the leaves

  adaptions-no end walls ,strengthed with lignin
• phloem: transports food substances such as sugar made in the leaves to the rest of the plant this is translocation

  adaptions-small pores in end walls to allow cell sap,elongated living cells
• root hair- absorbs water and minerals from soil
• meristem tissue- found in the tips of shoots and roots, and is able to change into different types of plant cell allowing plant to grow
• the leaf

  
• the upper epidermis is transparent and allows light to pass through it to the palisade layer
• the lower epidermis is full of holes called stomata which let co2 diffuse directly into the lead
• the rate of transpiration is affected by light intensity the brighter the light the greater the transpiration rate . stomata begin to close as it gets darker . photo synthesis can’t happen in the dark , so they don’t need to be open to let Co2 in
• factors affecting transpiration rate tempeture- the warmer it is the faster it happens because the water particles have more energy to evaporate and diffuse out the stomata
• factors affecting transpiration air flow - the better the airflow around the lead the greater the transpiration rate because it’s harder for diffusion to happen there is water outside of the leaf as well as inside it
• factors affecting transpiration humidity- the drier the leaf the faster transpiration happens
• measuring transpiration rate-pomometer- you can estimate the rate of transpiration by measuring the uptake of water by a plant because it is directly related to water loss
• guard cells- control the opening and closing of stomata to control the rate of gas exchange
• stoma- tiny pores on the underside of leaves that allow gases such as oxygen and carbon dioxide to enter or leave the leaf
• translocation- movement of dissolved substances through the phloem tissue from one part of the plant to another
• guard cell explained - when the plant is full of water the guard cells fill up and become turgid this makes the stomata open so gases can be exchanged for photosynthesis when the plant is short of water the guard cells lose water and become flaccid making the stomata close stoping loss of water vapour .
• guard cells adaptions- thin outer walls and thickened inner walls make the opening and closing work , sensitive to light and close at night to save water without losing out on photosynthesis , found on the underside of leaves because it is shaded and coller so less water is lost through the stomata