Lab 4

Question 1

what is phyllotaxy? What does it show?

Answer 1

Phyllotaxy is the the arrangement of leaves on a stem and shows certain patterns that allow leaves to take maximum advantage of available sunlight

Question 2

what are the three types of phyllotaxy?

Answer 2

alternate: one leaf per node
opposite: two leaves attach at a node
whorled: three or more leaves per node

Question 3

what are the two types of alternate phyllotaxy?

Answer 3

alternate distichous: leaves at 180 degrees from each other
alternate spiral (helical): leaves spiral around the stem

Question 3

what are the two types of opposite phyllotaxy?

Answer 3

opposite distichous: pairs of leaves are in a single plane
opposite decussate: successive pairs of leaves are at right angles to one another

Question 4

what does venation refer to?

Answer 4

the patterns of veins within the leaf

Question 5

what is the purpose of branching veins in a leaf?

Answer 5

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

Question 6

what is usually found in the adaxial surface of a leaf?

Answer 6

more photosynthetic cells, with more chloroplasts per cell, making it a darker green

Question 7

what is a ligule?

Answer 7

a flap-like structure found on some monocot leaves where the leaf blade meets the leaf sheath

Question 8

what makes a leaf sessile?

Answer 8

lack of a petiole

Question 9

what are stipules?

Answer 9

small flaps of tissue found on some eudicot leaves where the petiole joins to the stem

Question 10

simple leaves

Answer 10

leaves have a single leaf blade which is not divided

Question 11

compound leaves

Answer 11

the leaf blade is divided into two or more distinct leaflets

Question 12

what are the two types of compound leaves?

Answer 12

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

Question 13

how can you tell the difference between a leaf and a leaflet?

Answer 13

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

Question 14

what are the main functions of the stomata?

Answer 14

• gas exchange (CO2 for photosynthesis)
• creates major force for transporting water upward in the plant when water is lost through the stomata by transpiration

Question 15

what is an onion bulb? what is its purpose?

Answer 15

a modified bud with a very short underground stem which stores its food in thick, overlapping leaves

Question 16

what are bud scales? what are their functions?

Answer 16

short sessile leaves that are often hairy, hard, or resinous. function in protecting vegetative buds

Question 17

what is the function of guard cells?

Answer 17

regulate the opening and closing of the stoma, which allows gas exchange

Question 18

what is the function of the cuticle?

Answer 18

prevents excess water loss from leaf tissue exposed to sunlight and drying winds

Question 19

what are the characteristics of palisade mesophyll?

Answer 19

• 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

Question 20

what are the characteristics of spongy mesophyll?

Answer 20

• 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

Question 21

what does the vascular tissue system in leaves consist of?

Answer 21

veins of various sizes that branch throughout the palisade and spongy mesophyll layers

Question 22

what are the two types of ground tissue within the midrib?

Answer 22

• 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) `

Question 23

what are xerophytes?

Answer 23

plants which grow under conditions of limited water availability

Question 24

what are the characteristics of the pine leaf?

Answer 24

• a small surface area for its size
• a thick cuticle
• recessed stomata

Question 25

what is required for photosynthesis to occur?

Answer 25

sunlight, carbon dioxide, water, and plant pigments

Question 26

what is the function of the xylem in leaf veins?

Answer 26

brings water from the roots to the leaf tissue

Question 27

what is chlorophyll a?

Answer 27

the primary pigment involved in photosynthesis. absorbs light of violet, blue, and red wavelengths

Question 28

what is chlorophyll b?

Answer 28

an accessory pigment that absorbs light of blue, green, and orange wavelengths

Question 29

what are carotenoids (carotenes and xanthophylls)?

Answer 29

accessory pigments that absorb light of violet, blue, and green wavelengths