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Questions and Answers
What type of meristem is responsible for secondary growth in stems?
What is the function of cork tissue in plants?
Which cells are produced by the cork cambium?
Where is the vascular cambium located in the stem cross-section?
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Which cells contribute to the girth of the stem?
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What type of growth does the vascular cambium promote in stems?
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Terminal buds are responsible for which stem function?
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Which kind of meristem is primarily involved in stem elongation?
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What is the main function of the epidermis in stems?
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What type of cells have angular walls and are always present towards the upper epidermis in the distribution of water and food in leaves?
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Which part of the leaf is characterized by having thinner cuticle and larger pores that control gas exchange and water loss?
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What differentiates the internal structure of a monocot leaf from a dicot leaf in terms of mesophyll?
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What is the main function of the stomata in leaves?
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Which leaf structure is responsible for preventing excessive water loss in plants?
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In the internal anatomy of leaves, what is the main characteristic of phloem cells located below the xylem?
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Which cells are not generally differentiated into palisade and spongy mesophyll in a monocot leaf?
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What characteristic distinguishes the lower epidermis of a leaf from the upper epidermis?
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Which structure in leaves controls the exchange of gases and loss of water vapor?
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What is the primary function of the cuticle layer in leaves?
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Study Notes
External Structure of Stems
- A twig has nodes and internodes
- Node: the area where leaves are attached
- Internode: the area between nodes
- Petiole: the stalk that attaches the leaf blade to the stem
- Stipules: paired leaf-like appendages at the base of the petiole
- Lenticels: dark spots or elevations that allow gas exchange in the stem
Origin and Development of Stems
- Apical meristem: tissue in which cells actively divide, contributing to the increase in stem length
- Leaf primordia: tiny embryonic leaves that will develop into mature leaves
- The cells of the apical meristem undergo mitosis, giving rise to three primary meristems:
- Protoderm: gives rise to epidermis
- Procambium: produces primary xylem and primary phloem
- Ground meristem: produces two tissues composed of parenchyma cells, including pith and parenchyma tissue
Stem Functions
- Support leaves and reproductive structures
- Provide internal transport
- Produce new living tissues as roots do
Woody Twig
- Bud: an undeveloped shoot containing embryonic meristem
- Axillary bud: bud located in the axil, may develop into branches or flowers
- Terminal bud: often present at the tip of each twig
- Cork cambium: produces box-like cork cells impregnated with suberin, reducing water loss and protecting the stem
Herbaceous Eudicots
- Vascular bundle arrangement: in a circle around a central pith
- Epidermis: outer covering, provides protection
- Cuticle: waxy layer reducing water loss from the stem surface
- Cortex: a cylinder several cells thick, part of the plant's ground tissue system
- Vascular tissues: provide conduction and support
- Stele: central cylinder of a stem, includes xylem, phloem, and often pith
- Vascular cambium: single layer of cells sandwiched between xylem and phloem, responsible for secondary growth
Transpiration
- 90% of water loss occurs through stomata, mostly located on the lower epidermis of the leaf
- Guard cells regulate stomatal size
- Transpiration increases with:
- Low humidity
- High temperature
- Light
- Wind velocity
Guttation
- Exudation of water in the form of droplets from leaves through hydathodes
- Mostly noticeable in the early morning when grassy fields are moist with dew
Specialized Leaves
- Reproduction: plantlets or buds growing along notches, bases, apices, and tips of blades and petioles
- Aeration: enlarged petiole for buoyancy
- Support: presence of tendrils, hooks, and supporting leaf bases
- Protection: presence of bud scales, motile leaves, spines, stipules, and bracts
- Storage: dessert plants with succulent leaves that retain water
- Attraction: petaloid flower bracts or brightly-variegated leaves
- Absorption: insectivorous leaves; uncutinized leaves especially in some aquatic plants
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Description
Test your knowledge on the structure and development of stems, including topics like apical meristem, leaf primordia, leaf scars, and bundle scars. Learn about how tissue extends the length of twigs and the role of different cells in stem growth.
