plant tissues

Epidermal tissue

prevents water from escaping by evaporation due to the waxy cuticle

Palisade mesophyll tissue

positioned at the top of the leaf to receive a lot of light; lots of chloroplasts means more photosynthesis

Spongy mesophyll tissue

allows gases to diffuse in and out of cells due to the large air spaces

Guard cells

control the opening and closing of stomata depending on water availability

Xylem

transports water from roots to leaves in one direction as part of the transpiration stream; strong and waterproof due to lignin

Phloem

transports food substances (like sugars) to where they are needed in the plant; food can move in both directions (translocation)

Root hair cells

absorb more water and minerals due to their large surface area

Translocation

moves food substances made in the leaves up or down the phloem to parts of the plant where they are needed; driven by pressure differences

Transpiration

process where water is absorbed by roots, travels through the plant, and evaporates from the leaves via stomata

Light intensity

increases transpiration because more photosynthesis means stomata open wider, leading to more water loss

Temperature

increases transpiration by raising the rate of evaporation

Humidity

decreases transpiration by reducing the concentration gradient so less water diffuses out of the leaf

Wind speed

increases transpiration by removing humid air from around the leaf, increasing the concentration gradient

Water supply

affects transpiration; if water is low, the plant closes stomata to reduce water loss

Importance of transpiration

transports nutrients, cools the plant, and maintains turgor pressure

Xylem adaptation to form a continuous tube for water flow

consists of dead, hollow cells with no end walls

Xylem walls adaptation

walls are thickened with lignin, which strengthens them and makes them waterproof

Xylem adaptation flow

allows one-way flow of water from roots to leaves, matching the direction of transpiration

Phloem adaptation structure

made of living cells called sieve tube elements, with perforated end walls (sieve plates) to allow flow of sugars

Phloem adaptation flow

allows two-way flow of food substances depending on where they are needed in the plant