chapter 24 - reproduction and development of flowering plants Flashcards
What adaptations contribute to the reproductive success of angiosperms?
pollen, seeds, and flowers that develop into fruits
What are some examples of asexual reproduction in plants?
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
When are sexual and asexual reproduction each adaptive?
Sexual reproduction is adaptive when the environment is variable
Asexual reproduction is adaptive in a more stable environment
Describe alternation of generations in the plant life cycle
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
Describe the difference between pollination and seed dispersal
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.
What process begins endosperm formation?
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
How is the endosperm important to plants?
The endosperm nourishes the young plant until it begins producing its own food by photosynthesis
What are the components of a seed?
the seed is embryo and stored food surrounded by a seed coat
What are the two main functions of fruits?
Fruits protect developing seeds and promote their dispersal once they are mature
Why must seeds absorb water before germinating?
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
What are the events of early seedling development?
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
How does natural selection influence seed size?
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
What is a hormone?
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
How does a plant hormone exert its effects?
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
Describe the functions of the five major plant hormones.
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.
