Lab 4 Flashcards
what is phyllotaxy? What does it show?
Phyllotaxy is the the arrangement of leaves on a stem and shows certain patterns that allow leaves to take maximum advantage of available sunlight
what are the three types of phyllotaxy?
alternate: one leaf per node
opposite: two leaves attach at a node
whorled: three or more leaves per node
what are the two types of alternate phyllotaxy?
alternate distichous: leaves at 180 degrees from each other
alternate spiral (helical): leaves spiral around the stem
what are the two types of opposite phyllotaxy?
opposite distichous: pairs of leaves are in a single plane
opposite decussate: successive pairs of leaves are at right angles to one another
what does venation refer to?
the patterns of veins within the leaf
what is the purpose of branching veins in a leaf?
to provide “skeletal” support for the leaf and ensure that no leaf cell is far from a source of water and mineral nutrients or from a delivery point for the sugars produced by photosynthesis
what is usually found in the adaxial surface of a leaf?
more photosynthetic cells, with more chloroplasts per cell, making it a darker green
what is a ligule?
a flap-like structure found on some monocot leaves where the leaf blade meets the leaf sheath
what makes a leaf sessile?
lack of a petiole
what are stipules?
small flaps of tissue found on some eudicot leaves where the petiole joins to the stem
simple leaves
leaves have a single leaf blade which is not divided
compound leaves
the leaf blade is divided into two or more distinct leaflets
what are the two types of compound leaves?
pinnatley compound: leaflets are arranged like a feather along a common stalk called the rachis
palmately compound: all leaflets radiate out from a common point of attachment at the tip of the petiole. there is no rachis
how can you tell the difference between a leaf and a leaflet?
the presence of axillary buds: axillary buds are only produced in the axils of leaves where the petiole meets the stem. Axillary buds will not be present in the axils of leaflets
what are the main functions of the stomata?
- gas exchange (CO2 for photosynthesis)
- creates major force for transporting water upward in the plant when water is lost through the stomata by transpiration
what is an onion bulb? what is its purpose?
a modified bud with a very short underground stem which stores its food in thick, overlapping leaves
what are bud scales? what are their functions?
short sessile leaves that are often hairy, hard, or resinous. function in protecting vegetative buds
what is the function of guard cells?
regulate the opening and closing of the stoma, which allows gas exchange
what is the function of the cuticle?
prevents excess water loss from leaf tissue exposed to sunlight and drying winds
what are the characteristics of palisade mesophyll?
- tightly packed cells with many chloroplasts
- closest to the upper surface of the leaf and thus receive the greatest exposure to sunlight and are the major site for photosynthesis
what are the characteristics of spongy mesophyll?
- loosely packed cells that fill the area between the palisade mesophyll and the lower epidermis of the leaf
- connected with the stomata of the lower epidermis, allowing for efficient gas exchange
- also responsible for a considerable amount of photosynthesis
what does the vascular tissue system in leaves consist of?
veins of various sizes that branch throughout the palisade and spongy mesophyll layers
what are the two types of ground tissue within the midrib?
- collenchyma (a mass lying just under the upper epidermis, and a single row just above the lower epidermis)
-parenchyma (surrounds the midvein and other smaller veins) `
what are xerophytes?
plants which grow under conditions of limited water availability
what are the characteristics of the pine leaf?
- a small surface area for its size
- a thick cuticle
- recessed stomata
what is required for photosynthesis to occur?
sunlight, carbon dioxide, water, and plant pigments
what is the function of the xylem in leaf veins?
brings water from the roots to the leaf tissue
what is chlorophyll a?
the primary pigment involved in photosynthesis. absorbs light of violet, blue, and red wavelengths
what is chlorophyll b?
an accessory pigment that absorbs light of blue, green, and orange wavelengths
what are carotenoids (carotenes and xanthophylls)?
accessory pigments that absorb light of violet, blue, and green wavelengths
