Textbook (Raven Biology of Plants, 8th editions) 1. Formation of the Embryo; pp.
ID: 57659 • Letter: T
Question
Textbook (Raven Biology of Plants, 8th editions)
1. Formation of the Embryo; pp. 526–527, 529; moderate
Discuss the concept of polarity as it pertains to angiosperm embryogenesis.
2. Formation of the Embryo; p. 529; moderate
Define the term “primary meristem.” Name the three primary meristems, and name the tissue(s) into which each develops.
3. Formation of the Embryo; p. 529; moderate
List the principal stages of embryonic development in angiosperms, and describe the appearance of the embryo at each stage.
4. Formation of the Embryo; p. 530; difficult
The Arabidopsis gnom mutant (shown in Figure 22-5) consists of only a stem-like structure containing an epidermis, ground tissue, and vascular tissue. What typical embryonic parts is this seedling missing? What might be the function of the gnom gene in seedling development?
5. Formation of the Embryo; pp. 529–530; moderate
Give three examples of types of genes that govern Arabidopsis embryogenesis. What happens when these genes are mutated?
6. The Mature Embryo; pp. 530–531; difficult
A mutant garden bean seed is found that lacks endosperm. What would you expect this seed to look like? Name two other tissues that can have the same role as endosperm.
7. The Mature Embryo; p. 531; moderate
Explain the relationship between the epicotyl, the apical meristem, and the plumule.
8. The Mature Embryo; p. 531; moderate
Describe the various roles played by cotyledons in angiosperms.
9. Seed Maturation; p. 532; moderate
List the events that take place during the maturation phase of seed development. What is the difference between a dormant seed and a quiescent seed?
10. Requirements for Seed Germination; p. 533; moderate
Define seed dormancy. Are the packaged seeds that you buy at the store likely to be dormant? Why or why not?
11. Requirements for Seed Germination; pp. 533–534; moderate
What are the two most common causes of seed dormancy? Discuss some of the ways in which seeds can overcome dormancy.
12. From Embryo to Adult Plant; pp. 535–536; moderate
Onion (Allium cepa) and maize (Zea mays) are monocots, but they differ in certain features of germination. Outline these differences.
Explanation / Answer
Answer 1. Asymmetric cell division marks the beginning of embryogenesis in angiosperms.This asymmetric cell division is responsible for the concept of polarity. This division gives rise to apical (terminal) cells which are smaller and basal cells which are larger.The apical (terminal) cells gives rise to the plant embryo and the basal cells gives rise to the suspensor.
Answer 2. The primary meristem is mainly present at the tips of roots,axillary buds and stems and it results in increase in length and is present in the embryonic tissue.
The 3 primary meristems and the tissue into which it develops:
a). Protoderm- develops into dermal tissue.
b). Procambium-develops into vascular tissue and pericycle
c). Ground meristem-develops into cortex and endodermis.
Answer 3. Embryogenesis in angiosperms can be divided into the following satges:
a). Asymmetric cell division marks the beginning of embryogenesis in angiosperms.This division gives rise to apical (terminal) cells which are smaller and basal cells which are larger.The apical (terminal) cells gives rise to the plant embryo and the basal cells gives rise to the suspensor.
b). In the embryo specific pattern formation takes place.
c). Transition to the cotyledonary stage.
d).This is followed by root primordium initiation followed by shoot primordium initiation.
e).Germination of the matured embryo.
Answer 4. The Arabidopsis gnom mutant consists of only a stem-like structure containing an epidermis, ground tissue, and vascular tissue. The apical and basal regions of the embryo are missing.
The apical basal axis of polarity is determined by this gene.In membrane trafficking it regulates the formation of vesicles.
Answer 5. Gene At1g74960 encodes for keto acyl carrier protein synthase
Gene At1g34430 encodes for dihydro lipoamide S -acetyl transferase
Gene At1g33680 encodes for aminotransferase class I and II proteins.
Mutation of these genes results in abortion of embryo at preglobular stage.
Answer 6. Orchids lack endosperm.
The two other tissues that can have the same role as endosperm are cotyledons and perisperms.
Answer 7. The plumule is composed of epicotyl,apical meristem and leaves.All of them form parts of the embryo.
Answer 8. Roles played by cotyledons in angiosperms are as follows:
a). cotyledons are crucial for the growth of plants
b). cotyledon photosynthesis contributes to the axial growth in plants.
Answer 9. The events that take place during the maturation phase of seed development :
a). Loss of water
b).embryo becomes metabolically inactive
c).differentiation of storage cells and accumulation of storage compounds.
d) Transition from maternally controlled to filially controlled growth.
difference between a dormant seed and a quiescent seed:
the resting phase of a seed is called dormancy and there is no growth of the seed during this stage though favourable conditions for germination are present. It is due to the action of ABA hormone whereas a quiescent seed is unable to germinate due to adverse conditions for germination and is not due to any hormones.
Answer 10. the resting phase of a seed is called dormancy and there is no growth of the seed during this stage though favourable conditions for germination are present. It is due to the action of ABA hormone.
No, the packaged seeds are not dormant.because when they find favourable conditions they germinate which is not the case with dormant seeds.
Answer 11. two most common causes of seed dormancy:
a) Physical dormancy-some seeds have impermeable seed coat which is formed due to drying up of the seed or fruit.Common in angiosperms.
b)Chemical dormancy-some seeds become dormant due to presence of growth regulators in the coverings or around the embryo.
some of the ways in which seeds can overcome dormancy:
a)The growth regulators or chemicals present in dormant seed can be removed by washing the seeds or soaking them in water.
b)high temparature can be used to break dormancy
c)freezing can also be used
Answer12. Onion (Allium cepa) and maize (Zea mays) are monocots, but they differ in certain features of germination.
In Onion (Allium cepa) germination of seeds is epigeous whereas in maize (Zea mays) germination of seeds is hypogeous.
in maize (Zea mays) the stem comes out of the soil with leaves at the tip.
In Onion (Allium cepa) germination the stem comes out along with the cotyledons.these are not true leaves and they fall off when true leaves appear.
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