seeds and early development

Question 1

soil seed bank

Answer 1

all viable seeds found in the soil, duration of viability is variable anywhere from 5 to 2000 years

Question 2

seed composition

Answer 2

seed coat made of maternal tissue surrounding an embryo and a food source

Question 3

endosperm

Answer 3

food source found in the seeds of angiosperms, can be persistent or absorbed into the cotyledons which then become fleshy

Question 4

embryo

Answer 4

all contain a radicle (embryonic root), cotyledons (embryonic leaves), and a hypocotyl (embryo below cotyledons
some contain an epicotyl (embryo above cotyledons), and a plumule (tip of the epicotyl including true leaves and the apical meristem)

Question 5

funiculus

Answer 5

stalk that connects seeds to the ovary like an ambilocal cord

Question 6

hilum

Answer 6

scar on a seed coat where the funiculus was previously attached

Question 7

micropyle

Answer 7

small hole at the end of the hilum on the seed coat, functions in sperm entry to the ovule, water entry during development, and the weak point for radicle emergence

Question 8

advantages of seeds

Answer 8

they can wait to grow until the environment is more favorable, protect the embryo from harsh environments, allow the embryo to travel

Question 9

seed size

Answer 9

highly variable, smallest in orchids which have no endosperm and require a fungal partner to germinate, largest is the double coconut at 37lbs

Question 10

stages of embryo development

Answer 10

embryo growth and differentiation, seed expansion and endosperm accumulation, desiccation, quiescence, imbibition, germination

Question 11

desiccation

Answer 11

completely drying out of the seed to prevent rot

Question 12

quiescence

Answer 12

metabolically inactive state of seeds

Question 13

imbibition

Answer 13

rehydration that resumes metabolism

Question 14

germination

Answer 14

resumption of growth by a quiescent or dormant seed requiring at least, water, oxygen, and a minimum temperature

Question 15

dormancy

Answer 15

longer period of metabolic inactivity, that requires some extra step to germinate such as scarification, intense heat, stratification, alternating periods of cold and warm, chemical removal

Question 16

scarification

Answer 16

physical breakdown of the seed coat from a variety of sources such as animals digestion or repeated freeze thaw cycles

Question 17

intense heat

Answer 17

requirement to overcome dormancy that reduces the number of competitors and increases the nutrients in the soil

Question 18

stratification

Answer 18

requirement to overcome dormancy, extended period of cold

Question 19

seed coat dormancy

Answer 19

seed coat physically prevents water entry so germination cannot occur until it is removed

Question 20

embryonic dormancy

Answer 20

the embryo itself requires the required stimulus to germinate

Question 21

morphological dormancy

Answer 21

when the seed is fully developed the embryo is still in the globular stage

Question 22

photodormancy

Answer 22

embryo needs light

Question 23

thermal dormancy

Answer 23

embryo requires specific temperature conditions

Question 24

chemical dormancy

Answer 24

a chemical must be removed from the embryo

Question 25

viviparity

Answer 25

seed germinates while still in the fruit on the parent plant

Question 26

recalcitrant seeds

Answer 26

never fully desiccate, germinate as soon as the minimum requirements are met

Question 27

when germination occurs

Answer 27

seed imbibes water, embryonic root and shoot grow, radicle emerges, stem emerges, true leaves expand, there is a switch from stored nutrients to photosynthesis

Question 28

epigeous growth

Answer 28

cotyledons emerge above ground, hypocotyl forms a hook dragging cotyledons up, once above ground hook straightens and epicotyl grows

Question 29

hypogeous growth

Answer 29

cotyledons remain below ground and inside the seed coat, epicotyl forms a hook, emerges, straightens out, and the true leaves unfold

Question 30

elaiosome

Answer 30

fatty body on a seed attracts ants to carry seeds away

Question 31

non mutualistic seed dispersal

Answer 31

mechanisms of sticking to animals like burrs, ballistic, wind, or water dispersal