lecture 8: angiosperms - dispersal

Question 1

pericarp

Answer 1

◆ component of fruit – it’s “walll”
- the ovary wall becomes the thickened wall of the fruit

Question 2

dispersal (abiotic + biotic)

Answer 2

abiotic mechanisms:
◆ wind (winged or dust-like seeds)
◆ water (float on oceans, rivers, creeks)
◆ active propulsion (explosive dispersal)
◆ whole plant movement

biotic mechanisms:
◆ passively by adherence
◆ passively by consumption and excretion
◆ actively by nutrient provisioning
- cached fr seed reward and forgotten
- for a distinct nutrient reward
- by deception

Question 3

growth (building a sporophyte)

Answer 3

growth = increase in size of a tissue

occurs by one of two mechanisms:
(1) cell division – increasing cell number
(2) cell elongation – increasing cell size

two types:
a) primary growth – tissue elongation
b) indeterminate growth – a group of cells are self-renewing, and divide to produce new cells

Question 4

differentiation

Answer 4

the process of expressing the characteristics of a particular cell fate or tissue identity

• differentiation of the shoot and root systems occurs very early in embryonic development

Question 5

apical meristem (SAM / RAM)

Answer 5

two primary sites of cell division (at tips of the shoot and root apices (tops)):
1) shoot apical meristem
2) root apical meristem

◆ meristems contain plant stem cells
◆ origins of all new plant cells involved in primary growth are traced directly to either the SAM or the RAM

Question 6

germination (hypocotyl, epicotyl, radicle, coleoptile, apical hook)

Answer 6

hypocotyl:
- embryonic shoot below (“hypo”) the cotyledons
- emerges bent in an apical hook, protecting SAM as shoot grows to soil surface
- remains within seed during monocot germination

epicotyl:
- embryonic shoot above (“epi”) the cotyledons (tipped by SAM)
- emerges from seed coat during monocot germination sheathed by coleoptile (protective covering)

radicle:
- embryonic root (tipped by RAM)
- emerges from seed coat first during dicot and monocot germination

Question 7

the stem (nodes, internodes)

Answer 7

◆ nodes = sites where structures extend from the stem
◆ internodes = spans of stem betweed nodes

Question 8

the leaf (blade, petiole, axil)

Answer 8

• composed of blade and petiole (stem-like structure supporting the blade)
• axil: intersections where leaf meets stem