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Questions and Answers
What is the primary function of trichomes in the epidermis?
What is the primary function of trichomes in the epidermis?
Which type of mesophyll cell is primarily responsible for photosynthesis?
Which type of mesophyll cell is primarily responsible for photosynthesis?
What is the primary role of the spongy mesophyll?
What is the primary role of the spongy mesophyll?
In vascular bundles, what two components are primarily involved in the transport of water and nutrients?
In vascular bundles, what two components are primarily involved in the transport of water and nutrients?
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What is a significant histologic difference between dicots and monocots regarding epidermal cells?
What is a significant histologic difference between dicots and monocots regarding epidermal cells?
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What is a disadvantage of transpiration in plants?
What is a disadvantage of transpiration in plants?
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Where does guttation occur on a plant?
Where does guttation occur on a plant?
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Which process involves the reabsorption of sugars and minerals in plants?
Which process involves the reabsorption of sugars and minerals in plants?
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What structural change occurs in the abscission zone?
What structural change occurs in the abscission zone?
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What pigment replaces chlorophyll during the abscission process?
What pigment replaces chlorophyll during the abscission process?
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What is the primary function of leaves in terms of energy conversion?
What is the primary function of leaves in terms of energy conversion?
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Which type of leaf duration describes leaves that remain green for a year or more?
Which type of leaf duration describes leaves that remain green for a year or more?
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What tissue gives rise to the mesophyll in leaf development?
What tissue gives rise to the mesophyll in leaf development?
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Which leaf texture is described as being thick and fleshy?
Which leaf texture is described as being thick and fleshy?
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What structures in the leaf epidermis are responsible for gas exchange?
What structures in the leaf epidermis are responsible for gas exchange?
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Which type of leaf will unfold in spring and fall in autumn?
Which type of leaf will unfold in spring and fall in autumn?
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What provides additional protection against injury and water loss in leaves?
What provides additional protection against injury and water loss in leaves?
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Which cells are involved in regulating the opening and closing of stomata?
Which cells are involved in regulating the opening and closing of stomata?
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Which of the following is NOT classified as a type of floral leaf?
Which of the following is NOT classified as a type of floral leaf?
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What characterizes a petiolate leaf?
What characterizes a petiolate leaf?
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Which specialized leaf structure is designed for trapping insects?
Which specialized leaf structure is designed for trapping insects?
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What is a common effect of transpiration in plants?
What is a common effect of transpiration in plants?
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Which of the following helps to describe the morphology of leaves based on their attachment to the stem?
Which of the following helps to describe the morphology of leaves based on their attachment to the stem?
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Which type of leaf is characterized by the presence of hooks or tendrils?
Which type of leaf is characterized by the presence of hooks or tendrils?
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Which of the following environmental conditions influences transpiration rates in plants?
Which of the following environmental conditions influences transpiration rates in plants?
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Which of the following structures is NOT a type of leaf apex?
Which of the following structures is NOT a type of leaf apex?
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What distinguishes dicots from monocots regarding leaf glands?
What distinguishes dicots from monocots regarding leaf glands?
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Which statement about the palisade and spongy parenchyma of dicots and monocots is true?
Which statement about the palisade and spongy parenchyma of dicots and monocots is true?
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Which statement correctly describes the vascular bundles in dicots compared to monocots?
Which statement correctly describes the vascular bundles in dicots compared to monocots?
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What type of leaf is characterized as reduced foliage leaves in certain rhizomes and bulbs?
What type of leaf is characterized as reduced foliage leaves in certain rhizomes and bulbs?
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Which of the following leaf types serves as a common source of drugs?
Which of the following leaf types serves as a common source of drugs?
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What is the primary function of cotyledons in angiosperms?
What is the primary function of cotyledons in angiosperms?
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Which of the following statements regarding the product variety in dicots is accurate?
Which of the following statements regarding the product variety in dicots is accurate?
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In which type of leaves are modified leaves found that appear on the inflorescence axis?
In which type of leaves are modified leaves found that appear on the inflorescence axis?
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Study Notes
Leaves
- Flattened, rarely semi-centric or centric lateral expanse
- Seldom develops buds
- Located on the growing stem apex
Leaf Functions
- Conversion of inorganic matter to organic foliage
- Photosynthesis (sugar, starch, other complex substances)
- Assimilation (taking in of substances)
- Respiration
- Transpiration
Origin and Development of Leaves
- Dermatogen: located on the growing stem apex
- Periblem: gives rise to mesophyll
- Plerome: vascular tissue within the mesophyll
Leaf Texture
- Membranous: thin and pliable
- Succulent: thick and fleshy
- Coriaceous: thick and leathery
Leaf Duration
- Persistent/Evergreen: remains green for a year or more
- Deciduous: unfolding in spring, falling in autumn
- Caducous/Fugacious: falling early in the season
Epidermis
- Upper and lower surfaces of leaf blades
- Additional protection against injury
- Water loss
- Upper and lower epidermis
- Cuticle: waxy layer composed of cutin, varies in thickness
- Stomata: minute openings in the lower epidermis for gas exchange (average of 100 square millimeters)
- Guard cells: open and close stomata, lack chloroplasts
- Subsidiary cells: reservoir of water and ions
- Trichomes: hair-like structures, help reduce water loss, retain moisture, reflect sunlight, secrete irritants/excess salts
Mesophyll
- Gk. "middle of the leaf"
- Between epidermal layers
- Parenchyma cells with chloroplasts
- Palisade mesophyll: columnar cells, main site for photosynthesis, thicker when exposed to sunlight
- Spongy mesophyll: loosely and irregularly arranged, allows diffusion of gases
Veins/Vascular Bundle
- Extends through the mesophyll
- Extensive branching
- Xylem
- Phloem
- Bundle sheaths: one or more layers of non-vascular cells, surround larger cells, composed of parenchyma or sclerenchyma
Histologic Difference Between Dicots and Monocots
-
Dicots:
- Epidermal cells usually isodiametric
- Numerous but small stomata
- Non-glandular and glandular hairs are frequent
- Abundant leaf glands
- Water stomata over the upper surface are frequent
- Palisade and spongy parenchyma are distinct and former is denser
- Indurated vascular bundles
- Greater variety of accessory products of assimilation are developed
-
Monocots:
- Epidermal cells are elongated and equilateral
- Large stomata
- Hairs are rare
- Rare leaf glands
- Water stomata are absent or rare
- Palisade and spongy parenchyma are less dense and distinct
- Less indurated vascular bundles
- Comparatively small variety of accessory products of assimilation are developed
Types of Leaves
- Cotyledons: embryonic leaves, initial leaves
- Scale leaves: reduced foliage, certain rhizomes, above ground stems, and on bulbs
- Foliage leaves: common green leaves, photosynthesis, common source of drugs
- Bract leaves: modified leaves, appears on inflorescence axis
- Floral leaves: sepals, petals, microsporophyll, megasporophyll
According to Completeness
- Complete: lamina or leaf blade, petiole or leaf stalk, stipule
- Sessile: lamina directly attached to stem
- Petiolate
- Stipulate
- Exstipulate
Specialized Leaves
- Leaf tendrils, Hooks, Spines, Bud scales, Bracts, Bladder, Prophyll, Storage, Cotyledons, Insect-trapping, Reproductive, Phyllode, Flowerpot
According to Venation
- Cross-Venulate, Palmate, Longitudinal, Pinnate, Parallel (a), Dichotomous, Parallel (b), Arcuate, Reticulate, Rotate
According to Phyllotaxy
- Leaf arrangement (opposite, alternate, cauline leaves, decussate, whorled, distichous, clustered, scattered, rosulate, radical leaves, equitant, imbricate)
According to Leaf Apex
- Accuminate, Aristate, Obcordate, Acute, Cuspidate, Retuse, Obtuse, Mucreonate, Truncate, Caudate, Apiculate
According to Margin
- Entire, Crisped, Sinuate, Undulate, Lobed, Pinnatifid, Pinnatisect, Palmatifid, Crenate, Serrate, Serrulate, Dentate, Ciliate, Spinose, Runcinate, Incised, Laciniate, Dissected
Leaf Forms
- Linear, Oblong, Lanceolate, Oblanceolate, Cuneate, Spathulate, Ovate, Obovate, Elliptical, Rhomboid, Deltoid, Orbicular (also Peltate), Reniform, Cordate
Leaf Base
- Gradually tapering, Attenuate, Cuneate, Obtuse, Oblique, Rounded, Cordate, Sagittate, Hastate, Auriculate, Truncate, Divergent, Cleft
Physiology
Transpiration
- Water loss in plants, occurs through stomata
- Affected by environmental conditions (wind, temperature, relative humidity)
- Benefits: water movement, cooling off plants, accumulation of minerals
- Disadvantage: may cause wilting
Guttation
- Water is forced out of leaves, occurs at the tips of leaf veins known as hydathodes
Abscission
- Normal and seasonal falling off leaves or other plant parts
- Helps plants survive in low temperatures
- Process: plant reabsorbs sugar and essential minerals, Chlorophyll broken down, Red water-soluble pigments are synthesized, Stored in vacuole of leaf cells, Replaced by carotenoids and/or anthocyanins, Zone where leaves fall off, Structurally different from surrounding tissues, Development of suberized cork cells, Enzyme dissolve the middle lamella before the winter
Photosynthesis and Respiration
(Diagram shown)
End of Lecture
- Next topic: Metabolic Process in Plant Cells
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Description
Test your knowledge on plant structure and function with this quiz focusing on trichomes, mesophyll cells, vascular bundles, and photosynthesis. Explore the various roles of leaves and understand the differences between dicots and monocots. Challenge yourself with questions about transpiration and abscission processes.
