Leaf adaptations Flashcards
why are leaf adaptations important
the leaf of the plant functions as the food factory so therefore most of photosynthesis occurs in the leaf. Leaves are adapted in a specific way to make photosynthesis easir
what are some clever adaptations on the leaf
Leaves generally have athin,flatlamina(blade). This allows for anincreasedsurface area, increasing the amount ofsunlightthat can beabsorbed.Thethinnessof leaves allows foreasyandfastgas exchange to occur.
what do we know about the cross section of a leaf
Theuppersurfaceof the leaf is covered by awaxy cuticlelayer. This structureprevents water lossfrom the leaf during hot weather. It is important to note that the waxy cuticle istransparent– this means that thesunlightcan pass through it to the cells lower down wherephotosynthesisoccurs.
Theundersideof the leaf contains many smallopenings. These are calledstomata(singular: stoma). Stomata allowgas exchangeto occur, taking incarbon dioxideand releasingoxygenback into the atmosphere. The openings of the stomata are controlled byguard cells. The guard cells open the stomata when carbon dioxide is needed but close them when water loss needs to be prevented.
structure of the leaf (continued)
Thedermaltissueof a leaf is theepidermis. Theupper epidermisis found directly below the waxy cuticle, and thelower epidermisis on the underside of the leaf, surrounding the stomata. The epidermis protectsthe leaf but is a verythinlayer. This allows thesunlightto pass through to the lower cells.
Below the upper epidermis is thepalisade mesophylllayer. This is part of thegroundtissue. The palisade cells contain manychloroplastsand it is here where the majority ofphotosynthesisoccurs. These are found on the upper side of leaf so that they can easily obtain thesunlightthat is needed for photosynthesis!
Beneath thepalisade mesophyll layer, and above the lower epidermis, is thespongy mesophyll. This also forms part of theground tissue.There are manyair spacesbetween thespongy mesophyllcells. These air spaces allow for therapid diffusionof gases.Oxygendiffuses out of the cells and is released back into the atmosphere, whilecarbon dioxidediffuses into the cells where it will be used for photosynthesis.
The final tissue type found in leaves is thevascular tissuewhich is found invascular bundles. The vascular bundles are essential fortransportin plants.
Xylemvessels transportwateraround the plant, from the roots and into the leaves, where it enters the palisade mesophyll cells and is used forphotosynthesis.
Phloemvessels transportfoodaround the plant. Onceglucosehas been synthesised in the leaves duringphotosynthesis, it must be transported to cells around the plant forcellular respiration.
