chapter 24 - reproduction and development of flowering plants Flashcards

1
Q

What adaptations contribute to the reproductive success of angiosperms?

A

pollen, seeds, and flowers that develop into fruits

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2
Q

What are some examples of asexual reproduction in plants?

A

some plants, like aspen trees, can form clones called suckers that are connected to a common root system. Kalanchoe plants produce identical plantlets from portions of their leaves. In many plants, a severed stem can grow roots and develop into a new plant that is a clone of the parent

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3
Q

When are sexual and asexual reproduction each adaptive?

A

Sexual reproduction is adaptive when the environment is variable

Asexual reproduction is adaptive in a more stable environment

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4
Q

Describe alternation of generations in the plant life cycle

A

plants have a haploid gametophyte generation and a diploid sporophyte generation. the gametophyte generation produces haploid gametes by mitosis. Male and female gametes fuse in fertilization. The product of fertilization is the zygote, which develops into the mature sporophyte. Meiosis in the sporophyte produces haploid spores, which develop into gametophytes

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5
Q

Describe the difference between pollination and seed dispersal

A

pollination is the transfer of pollen from an anther to a stigma; the result of pollination is fertilization.

Seed dispersal is the transport of seeds from the parent plant via animals, wind, or water. the result of seed dispersal is minimal competition between parent and offspring.

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6
Q

What process begins endosperm formation?

A

Endosperm forms by double fertilization, during which one sperm nucleus fertilizes the egg and the other sperm nucleus fertilizes the central cell forming the endosperm

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7
Q

How is the endosperm important to plants?

A

The endosperm nourishes the young plant until it begins producing its own food by photosynthesis

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8
Q

What are the components of a seed?

A

the seed is embryo and stored food surrounded by a seed coat

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9
Q

What are the two main functions of fruits?

A

Fruits protect developing seeds and promote their dispersal once they are mature

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10
Q

Why must seeds absorb water before germinating?

A

the seed expands as it absorbs water, which helps the seed coat to split and exposes the embryo to release hormones that trigger the production of enzymes that digest stored starch, which will nourish the young seed until it begins to produce its own food by ps

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11
Q

What are the events of early seedling development?

A

after seed germination, cells in the embryo’s apical meristems divide to form shoots and roots. gravity stimulates the downward growth of roots. at first, the only source of energy is stored food from the seed. but the seedling produces its own food by ps once leaves form on the seedling’s stem

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12
Q

How does natural selection influence seed size?

A

seed size reflects a trade-off between nutrient storage and dispersal. small seeds can disperse far away from the parent plant, but they contain little energy to sustain early seedling growth. conversely, large seeds contain abundant energy but may not disperse easily to new habitats

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13
Q

What is a hormone?

A

a hormone is a biochemical synthesized in small quantities that is transported to other locations in the organism, where it stimulates or inhabits a response in target cells

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14
Q

How does a plant hormone exert its effects?

A

plant hormones bind to a receptor protein on or in a target cell. stimulating chemical reactions that alter the expression of one or more genes

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15
Q

Describe the functions of the five major plant hormones.

A

auxins stimulate cell elongation in stems and fruits; participate in tropisms, stimulate growth of roots from stems cuttings; and inhibit growth of lateral buds, and they delay leaf senescence.
Cytokinin stimulate cell division and the growth of lateral buds, and they delay leaf senescence
gibberellins stimulate cell division and cell elongation in roots, shoots, and young leaves, and they trigger seed germination. ethylene ripens fruits and stimulates leaves and flowers to senesce and drop from the plant; it also participates in thigmotropism.

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16
Q

Pruning stimulates the growth of new branches. What hormonal changes occur in the lateral buds after the shoot tip is pruned?

A

removal of a shoot tip decreases the concentration of auxins and increases the concentrations of cytokinin’s at the lateral buds. this hormonal signal triggers cell division in the lateral buds, which eventually develop into new branches

17
Q

What is auxin’s role in phototropism?

A

auxin moves to the shaded side of a shoot, where it triggers cell elongation. by causing unequal cell growth on opposite sides of a shoot, auxins cause the plant to bend toward light.

18
Q

How do photoreceptors help regulate seed germination, circadian rhythms, and flowering?

A

germination: ps is a photoreceptor turned to red light and wavelengths. red light causes the inactive P form of phytochrome to convert to active P that travels to the nucleus and influences expression of key genes
circadian rhythms: phytochrome and cryptochrome help to reset a plant’s biological clock as light conditions change
flowering; phytochrome informs the plant of the length of an uninterrupted dark period, stimulating the release of the flowering hormone at the appropriate time of yr

19
Q

How do long-day plants differ from short-day plants?

A

long-day (short-night) plants flower only when nights are shorter. short day (long night) plants flower only when uninterrupted dark periods become longer than some. long day plants usually bloom in the spring or early summer and short day plants flower in late summer or fall

20
Q

How do statoliths and auxins participate in gravitropism?

A

starch-rich plastids called statoliths are the gravity detectors in the root cap cells. the statoliths sink to the bottom of the cells, redistributing auxins, which inhibit cell elongation in roots. if a plant is turned on its side, the root turns downward as cells on the upper side of the root elongate more rapidly than those on the lower side

21
Q

How does thigmotropism help some plants climb?

A

thigmotropism is a response to touch in a specialized structure such as a tendril. hormones cause differential growth in the tendril, allowing it to encircle physical supports such as a trellis or the branches of another plant

22
Q

How does seed dormancy promote reproductive success?

A

seed dormancy allows a seed to germinate in favorable conditions, rather than in the cold winter months when sunlight is scarce and water is frozen in the soil

22
Q

How does seasonal dormancy in deciduous plants promote reproductive success?

A

allows a plant to withstand the freezing temperatures of winter by reducing water loss, slowing metabolism, and producing sugars and amino acids that act as an antifreeze

23
Q

What are some conditions that can release a plant from dormancy?

A

longer days, warmer temperatures, and moisture can release a plant from dormancy