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62801
Transport in plants
Descrição
A-Level Biology Mapa Mental sobre Transport in plants, criado por savanna q em 30-04-2013.
Sem etiquetas
biology
biology
a-level
Mapa Mental por
savanna q
, atualizado more than 1 year ago
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Criado por
savanna q
mais de 11 anos atrás
874
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Resumo de Recurso
Transport in plants
xylem
xylem vessels move water from the roots of a plant to their leaves
water is absorbed through root hair cells
water is transported through the xylem vessels, up the stem, to the leaves
water evaporates from the leaves
transpiration
xylem vessels consist on dead cells. They have a thick, strengthened cellulose wall with a hollow lumen
Phloem
phloem consists of columns of living cells
phloem vessels are involved in translocation.
(translocation is the transport of dissolved material within a plant)
the movement of food substances from the stems to growing tissues and storage tissues
phloem transports food from the leaves to the rest of the plant.
Adaptations
A healthy plant must balance its water loss from the leaves with its uptake of water through the roots. Transpiration provides plants with water for:
Cooling
Photosynthesis
Support
Movement of minerals
root hair cells = larger surface area to take up water by osmosis
not enough water = flaccid + wilting
the structure of the leaf is adapted to reduce excessive water loss:
They have a waxy cuticle
only a small amount of stomata on the upper surface
guard cells around the stomata
when it's really bright and there's lots of water then the plant changes:
chloroplasts make sugars at a higher rate
waters enters the guard cells from other cells via osmosis
the guard cells become turgid
the stomatal opening gets bigger
transpiration
water moves against gravity in xylem cells
water on the surface of spongy and palisade cells evaporates and diffuses out of the leaf
more water is drawn up through the continuous tube (xylem); producing a flow of water + dissolved minerals from roots to leaves
when water is scarce or the roots are damaged, the transpiration rate slows down
plants then wilt
factors that affect transpiration:
light intensity
transpiration increases when it is bright
the stomata open wider to allow more carbon dioxide in for photosynthesis
humidity
transpiration is slower when it is humid
the water concentration is already high outside so water won't diffuse out
wind
transpiration is faster when it is windy
water vapour is moved quickly by air movement, speeding up diffusion
temperature
transpiration in faster when it is hot
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