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Leaf
,→Key Stage 4
===Meaning===
A [[leaf]] is an [[organ]] in the [[Shoot System|shoot system]] of a [[plant]] that uses [[photosynthesis]] to [[Producer|produce]] food for the [[plant]].
===About Leaves===
: The [[Cell (Biology)|cells]] in '''leaves''' have many [[chloroplast]]s inside them for [[photosynthesis]].
: '''Leaves''' produce food that is sent to the [[root]]s through the [[phloem]] by [[translocation]].
'''Leaves''' have many [[tissue]]s inside them found in layers:
*Upper Epidermis - A layer of cells at the top of the leaf that make a waxy cuticle on top to keep the [[leaf]] waterproof.
*[[Palisade Tissue]] - A layer of [[Palisade Cell|palisade cells]] which have lots of chloroplasts in them for [[photosynthesis]].
*[[Spongy Mesophyll Tissue]] - A layer of [[Spongy Mesophyll Cell|spongy mesophyll cells]] that have irregular shapes to allow [[air]] to pass through the [[leaf]].
*Lower Epidermis - A layer of [[Cell (Biology)|cells]] at the bottom of the [[leaf]] with [[Stoma|stomata]] to allow [[air]] into and out of the [[leaf]].
{| class="wikitable"
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|[[File:LeafCrossSectionDiagram.png|center|600px]]
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| style="height:20px; width:600px; text-align:center;" |A [[diagram]] of the cross section of a [[leaf]] showing [[Palisade Cell]]s, [[Spongy Mesophyll Cell]]s and [[Guard Cell]]s.
|}
===Adaptations for Photosynthesis===
: '''Leaves''' have [[air]] gaps between the [[Spongy Mesophyll Cell|spongy mesophyll cells]] to allow [[Gas Exchange in Plants|gas exchange]].
: [[Xylem Tissue]] transports [[water]] to the '''leaves''' for [[photosynthesis]].
: '''Leaves''' usually have more [[Guard Cell|guard cells]] and around a [[Stoma|stomatastoma]] on the underside (lower epidermis) than the top side (upper epidermis). These close which closes when the [[leaf]] gets [[dehydrate]]d, stopping [[Carbon Dioxide|carbon dioxide]] getting into the [[leaf]] which . This stops them using [[water]] for [[photosynthesis]]and helps protect the plant from further dehydration.: '''Leaves''' usually have more [[Guard Cell|guard cells]] and [[Stoma|stomata]] on the underside (lower epidermis) than the top side (upper epidermis) because [[stoma|stomata]] on the top side would lose [[water]] more quickly, increasing the rate of dehydration.