TwoOldGuys™ Study Guides
BI-125 Botany
Leaf
Overview
- primary photosynthetic organ of plants
- epidermis
- mesophyll
- veins [vascular bundles]
Development
- pumule of embryo becomes first leaves
- cotyledons of embryo may emerge as embryo leaves
Anatomy, gross
Anatomy, tissue level
- growth from apical meristems on vein tips
- intercalary meristems of grasses at leaf base
- seasonal, deciduous leaves
- abcisson layer at base of petiole
- chlorophyll typically withdrawn prior to leaf fall
- accessory pigments may not be withdrawn
- summer-green leaves with leaf fall before winter
- wet season leaves with leaf fall at start of dry season
- some tropical deciduous species have synchronous leaf fall [1 day]
blade
upper epidermis with cuticle
palisade mesophyll, photsynthetic
spongy mesophyll, photsynthetic with air spaces
vascular bundles [veins]
lower epidermis
- thin cuticle
- stomata, except in grasses where stomata in upper epidermis
Petiole
- simple leaves
- compound leaves
- pinnate [with rachis]
- palmate
- double compound (pinnate)
- bulliform cells
- abcission layer at base of petiole
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