Lecture 6 Flashcards
what roles does a fruit play in the life cycle of an angiosperm
protection of seeds, dispersal of seed (abiotic and biotic)
what is the placenta
portion of the ovary where ovules originate to and which they remain attached after fertilization
what is the parietal arrangement of seeds
ovules borne on ovary wall or its extension
- mustard, cucumber
what is the axile arrangement of seeds
ovules borne on central tissue in a partitioned ovary with as many locules (sections) as the carpels
- citrus, tomato, okra
what is the free central arrangement of seeds
ovules borne on central tissue not connected to ovary wall
- bell pepper
what is the marginal arrangement of seeds
placenta formed as a ridge along ventral suture of ovary. ovules borne in two rows
- beans, peas
what is basal arrangement of seeds
placentation in a unilocular ovary
- sunflower
what are cotyledons
embryonic leaves, different from a post germinative true leaf
differentiate between monocots and dicot embryos
monocots have one cotyledons, dicots have two cotyledons
what happens in many dicots
the nutritive endosperm gets used up by the developing embryo and results in large cotyledons as food stores
what is different about endospermic dicots
they have thin cotyledons
what is the epicotyl vs hypocotyl
epicotyl above cotyledon; is stemlike with one of more leaves, the hypocotyl is stemlike portion between the primary shoot and primary root
what is the poaceae family
includes some grasses such as wheat, rice, maize
what is the scrutellum
large cotyledon attached to one side of the embryo axis in poaceae
- absorbative and in contact with endosperm
what is the radicle
the root pole at the lower end with sheathing coleorhiza
what is the plumule
the shoot end at the upper side with sheathing coleoptile
coleorhiza vs coleoptile
coleorhiza is at the radicle (root end) and coleoptile is at the plumule (shoot end)
what is the aleurone
living outermost cell layer of the endosperm
how do things like corn become a single seeded fruit
the testa fuses with the pericarp
what happens to seeds in order for them to enter quiescence
the testa hardens, becomes impervious and looses water so the embryo exists in a highly dessicated and anoxic state
what is quiescence
a state of minimal or basal activity - resting
is quiescence the same as dormancy
NO!
what makes dormancy different from quiescence
dormancy involves a very precise combination of factors
what is imbibition
uptake of water by a seed to cause swelling and rupture of the seed coat
what is the role of mucilage
plays an important role in germination and seedling establishment
what is GA and where is it synthesized
gibberellic acid, regulates reserve mobilization, is synthesized in the cotyledon and embryo
what is skotomorphogenesis
morphogenesis in absence of light - results in etiolated seedlings
what is photomorphogenesis
morphogenesis in the presence of light - doesn’t result in etiolation
why is the hypocotyl bent during morphogenesis
to protect the SAM from injury
what are phytochromes
light responsive pigment proteins which sense the presence, intensity, duration, direction, and quality of light - they play a huge roll in de-etiolation
what is cryptochrome
absorbs UV and blue parts of the spectrum and affects the process of photosynthesis
what is epigeal vs hypogeal
epigeous germination: cotyledons are lifted out of the soil as the apical hook becomes straight and epicotyl bearing foliage grows upwards (bean)
hypogea’s germination: cotyledons borne on the hypocotyl remain below the soil while the epicotyl emerge above (pea)
what is the difference between monocot and dicot roots
monocots have multiple/fibruous roots; dicots have a single tap root with lateral extension
what are adventitious meristems
non-embryonic, meristems arising in positions other than normal; supportive of vegetative growth and part of the asexual strategy of propagation
what is an example of adventitious roots
the roots on the branches of ivy, roots on the babies of a spider plant (come off of a shoot)
what is an example of adventitious shoots
bryophyllum leaves
- an asexual strategy occurring on the notches of the leaves ; shoots lying all around the parent plant on agave plants
