Page 23 - Ranger SPM 2022 Biology

Biologi SPM Bab 2 Struktur dan Fungsi daun

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Palisade mesophyll cell • Long cylinder shaped cells which are vertically and closely arranged • Have highly packed chloroplasts to maximise absorption of sunlight • Cell wall covered with a layer of water to dissolve carbon dioxide before it is absorbed Spongy mesophyll cell • Uneven shaped cells which increase surface area for gaseous exchange • Cells are loosely arranged with lots of air s

into cell

Stomata • Opening for gaseous exchange between leaf and atmosphere • Most stomata are on lower epidermis to reduce water loss from leaf

• Protect leaves from physical injury and pathogen attacks • No chlorophyll • One cell thick layer which is transparent to allow sunlight to reach chloroplasts of cells beneath it Guard cells • Consist of chloroplasts to carry out photosynthesis • Regulate transpiration rate by controlling the opening and closing of stomata
Form 5

Upper epidermis Figure 2.7 Adaptations of leaf structure for photosynthesis

• A layer of water impermeable of sunlight Xylem • Transport water and minerals from roots to leaves for photosynthesis Phloem • Transport products of photosynthesis from leaves to other part of plant Lower epidermis • No chlorophyll except in guard cells

Cuticle wax to reduce water loss from • Transparent to allow penetration

leaf

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