CHP 42 Plant Reproduction
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KristinP1713 on March 4, 2012
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205 terms
Terms | Definitions |
|---|---|
 what is phase change | internal development changes that allow plants to obtain competence to respond to external or internal signals (or both) that triggers flower formation |
| true or false: it is easier to get a plant to revert from an adult to juvenile state than to induce phase change experimentally | true |
| describe the experiment done with the embyronic flower (emf) mutant of Arabidopsis flowers | it flowers almost immediately which is consistent with the hypothesis that the wild-type allele suppresses flowering; as wild type plant matures, the EMF expression decreases; findings suggested that flowering is the default state, and that mechanisms have evolved to delay flowering (allows the plant to store more energy to be allocated for reproduction) |
| what does phase change require | a sufficiently strong promotive signal and the ability to percieve the signal |
| what does phase change result in | results in an adult plant, but not necessarily a flowering plant |
| true or false: the ability to reproduce is distinct from actual reprodcutive development | true |
| what are the four genetically regulated pathways to flowering that have been identified | 1.) light-dependant pathway 2.) temperature-dependent pathway 3.) gibberellin-dependant pathway 4.) autonomous pathway |
| what can promote or repress flowering | the environment |
| what is vernalization | the requirement for a period of chilling of seeds or shoots for flowering |
| what does vernalization affect | the temperature-dependant pathway |
| what is the photoperiodic pathway | the light-dependant pathway; aspects of growht and development are keyed to changes in the proportion of light to dark in teh daily 24-hr cycle (Day length) |
| describe the flowering responses of plants to day length that are short-day plants | flowering is initiated when daylight becomes shorter than a critical lenght |
| describe the flowering responses of plants to day length that are long-day plants | flowering begins when daylight becomes longer |
| what are day-neutral plants | flower when mature regardless of day length, as long as they have recieved enough light for normal growth; snapdragons and roses are examples |
| is it the amount of light or darkness that determines whether a plant flowers? | the amount of darkness |
| when does flowering occur in obligate long day plants | when the night length is less that the maximal amount of required darkness (critical night length) for hte species |
| when does flowering occur in obligate short day plants | amount of darkness must exceed the critical night lenght for the species |
| flowering occurs more rapidly or slowly depending on what | the lenght of the day |
| what are facultative long- or short-day plants | when flowering occurs more rapidly or slowly depending on the length of the day but these plants rely on other flowering pathways as well; their photoperiodic requirements is not absolute |
| what are the advantages of photoperiodic control of flowering | permits plants to flowers when abiotic environmental conditions are optimal, pollinators are available, and competition for resources with other plants may be less |
| at middle latitdues, when do most long-day plants flower | in the spring and early summer |
| when do most short-day plants flower | in late summer and fall |
| what can the flowering responses to day length determine | the geographic distribution of certain plants |
| what is photoperiod perceived by | several different forms of phytochrome and by a blue-light sensitive molecule cryptochrome |
| what does phototropin affect | photomophogenesis |
| what does cryptochrome affect | photoperiodic responses |
| what is light linked to | the circadian rhythm regulated by an internal clock that facilitates or inhibits flowering |
| what light receptor is phytochrome | red-light receptor |
| what light receptor is cryptochrome | blue-light receptor |
| what gene do phytochrome and cryptochrome use to regulate flowering | the CONSTANS (CO) gene |
| how are CO protein levels modulated | through the action of cryptochrome |
| what does CO do | it is an important protein because it links the perception of day length with the production of a signal that moves from the leaves to the shoot where a change in gene transcription leads to the production of flowers |
| when are levels of CO lower | levels of CO are lower at night because of targeted protein degradation |
| what stabilizes CO during the day and protects it from ubiquitination and subsequent degradation | blue light acting via cryptochrome |
| what does CO result in the expression of | it is a transcription factor that results in the expression of LFY |
| what is LFY | one of the key genes that tells a meristem to switch over to flowering |
| what are three possibilities about the existence of a flowering hormone | that CO protein is a graft-transmissable flowering signal or that it affects such a signal; because that CO is found in the phloem it is possible that this is the protein that moves in the grafted plant to cause flowering; possibility that CO directly or indirectly affects a separate graft-transmissable factor that is essential for flowering |
| how does cold temperature affect flowering | can accelerate or permit flowering in many species |
| what is vernalization | when plants require a period of chilling before flowering |
| who discovered vernalization | T. D. Lysenko; ukranian scientist |
| how did Lysenko discover vernalization | while trying to solve the problem of winter wheat rotting in the fields; chilled the seeds and then planted them in the spring causing them to sprout and grow; however he incorrectly concluded that he had converted one species, winter wheat, into another, spring wheat, by simply altering the environment |
| when is vernalization necessary for plants | in later stages of development |
| what is the effect of decreased levels of gibberellins | delays flowering |
| what does gibberellins do | enhance the expression of LFY; it actually binds the promoter of the LFY gene so its effect on flowering is direct |
| is the effect of gibberellins on flowering direct or indirect | direct |
| what does the autonomous pathway to flowering depend on | it does not depend on external cues except for basic nutrition |
| what was the first pathway to evolve | autonomous pathway |
| what type of plants depend primarily on the autonomous pathway | day-neutral plants |
| what delays flowers in relation to roots and stems | the addition of roots, and not the loss of leaves, delays flowering |
| what may regulate when flowering occurs | balance between floral promoting and inhibiting signals |
| what do the four flowering pathways lead to | an adult meristem becoming a floral meristem by either activating or repressing the inhibition of floral meristem identity genes |
| what are two of the key floral meristem identity genes | LFY and AP1 |
| what do LFY and AP1 establish | the meristem as a flower meristem; they turn on floral organ identity genes |
| what do the floral organ identity genes define | four concentric whorls, moving inward in the floral meristem |
| what are the four concentric whorls | sepal, petal, stamen, and carpal |
| what is the ABC model developed for | to explain how three classes of floral organ identity genes could specify four distinct organ types |
| what does the ABC model propose | that three classes of organ identity genes (a, b, and c) specify the floral organs in the four floral whorls |
| what are four points researchers have determined from the about the ABC model | 1.) Class A genes alone specify the sepals 2.) Class A and B genes together specify the petals 3.) class b and c genes together specify the stamens 4.) class c genes alone specify the carpals |
| what are floral parts thought o have evolved from | leaves |
| what would be predicted if the floral organ identity genes are removed | whorls of leaves, rather than sepals |
| what are the ABCDE organ identity genes? | transcription factors that turn on many more genes that actually give rise to the three-dimensional flower |
| what does the flower house | the haploid generations that will produce gametes |
| what does the flower function to increase | functions to increase the probability that male and female gametes from different plants will unite |
| what is the diversity of angiosperms partly due to | the evolution of a great variety of floral phenotypes that may enhance the effectiveness of pollination |
| how many whorls does a complete flower have | four whorls |
| what are the four whorls in a complete flower | calyx, corolla, androecium, and gynoecium |
| what is different about an incomplete flower | lacks one or more of the whorls |
| what is the calyx | the outermost whorl; it consists of flattened appendages, called sepals, which protect the flower in the bud |
| what are sepals | flattened appendages that make up a calyx |
| what is a corolla | a collection of petals; may be fused |
| what is the function of petals mainly | to attract pollinators |
| what do the calyx and corolla do | they are not directly involved in gamete production or fertilization but they enhance reproductive success |
| what is androecium | collective term for all the stamens (male structures) of a flower |
| what are stamens | all the male structures of a flower; bear the angiosperm microsporangia |
| what is the anther | a swollen portion in the apex of a filament that contains four microsporangia |
| describe a stamen in an angiosperm | has filaments (stalks) that are slender and often threadlike; four microsporangia are evident at the apex in a swollen portion called the anther |
| what is the gynoecium | a collective term for all the female parts of a flower; consists of a single carpel or two or more fused carpels |
| what are single or fused carpels referred to as | simple or compound pistils |
| what kind of pistils do tomatoes and oranges have | compound pistil |
| what do ovule develop into | seeds |
| where are ovule produced | in the pistils swollen lower portion, the ovary |
| what is the ovary | the pistils lower swollen portion |
| describe the ovary | narrows at the top into a slender, necklike style with a pollen receptive stigma at its apex |
| what are carpels essentially | rolled floral leaves with ovules along the margins |
| what does fusing of the carpel margins ultimately result in | a pistil |
| what are the two major evolutionary trends that led to the wide diversity of modern flowering plants | 1.) separate floral parts have grouped together, or fused 2.) floral parts have been lost or reduced |
| what is unique about the number of parts in each whorl in more advanced angiosperms | the number of parts in each whorl has often been reduced from many to few |
| describe the trends in floral specialization | given way to single whorl at each level; central axis of many flowers has shortened; whorls are close to one another; members of one or more whorls have fused with one another, sometimes joining into a tube; different whorls may be fused together; whole whorls may be lost from the flower |
| what do modifications often relate to | pollination mechanisms |
| what kind of symmetry are primitive flowers | radially symmetrical |
| what is radial symmetry | one could draw a line anywhere through the center and have two roughly equal halves |
| what kind of symmetry do advanced flower groups have | bilaterally symmetrical |
| what is bilateral symmetry | divisible into two equal parts along only a single plane |
| what is bilateral symmetry often associated with | advanced and highly precise pollination systems |
| what gene regulates floral symmetry | CYCLOIDIA |
| what happens to flowers in the absence of CYCLOIDIA | flowers are more radial |
| how have humans influenced floral diversity | humans have selected for practical or aesthetic traits that may have little adaptive value to species in the wild |
| what does reproductive success depend upon | uniting the gametes found in the embryo sacs and pollen grains of flowers |
| what is alternation of generations | in which a diploid sporophyte generation gives rise to a haploid gametophyte generation |
| describe the gametophyte generation in angiosperms | the gametophyte generation is very small and is completely enclosed withing the tissues of the parent sporophyte |
| what are the male gametophytes (microgametophytes) in angiosperms | pollen grains |
| what are the female gametophytes (megagametophytes) in angiosperms | embryo sac |
| true or false: angiosperms have separate structures for producing male and female gametes | true |
| what are two ways that the reproductive organs of angiosperms are different from those of animals | 1.) both male and female structures usually occur together in the same individual flower 2.) angiosperm reproductive structures are not permanent parts of the adult individual |
| describe anthers | they contain four microsporangia that produce microspore mother cells (2n) |
| describe pollen formation | anthers contain four microsporangia that produce microspore mother cells (2n); microspore mother cells produce microspores (n) through meiotic cell division; these become pollen through mitosis and wall differentiation; inside each pollen grain is a generative cell that later divides into two sperm cells |
| what does fertilzation require of the pollen grain | that the pollen grain grow a tube that penetrates the style until it encounters the ovary |
| describe embryo sac formation | eggs develop in the ovules of the angiosperm flower; within each ovule is a megaspore mother cell; megaspore mother cell undergoes meiosis to produce four haploid megaspores; only one megaspore survives while the rest are absorbed by the ovule; lone megaspore enlarges and undergoes repeated mitotic divisions to produce eight haploid nuclei that are enclosed within a seven-celled embyro sac |
| describe the arrangement of the embryo sac | one nucleus is located near the opening of the embryo sac in the egg cell; two others are located together in a single cell in the middle of the embryo sac (polar nuclei); two more nuclei are contained in individual cells called synergids that flank the egg cell; the other three nuclei reside in cells called the antipodals located at the end of the sac, opposite the egg cell |
| where are the polar nuclei located | together in a single cell in the middle of the embryo sac |
| what are the synergids | individual cells that each contain a nuclei and flank the egg cell |
| what is the first step in uniting the two sperm cells in the pollen grain with the egg and polar nuclei | germination of pollen on the stigma of the carpel and it growth toward the embryo sac |
| what is pollination | the process by which pollen is placed on the stigma |
| what is self-pollination | when pollen from a flower's anther pollinates the same flower's stigma |
| what is cross-pollination (outcrossing) | when pollen from the anther of one flower pollinates the stigma of a different flower |
| describe pollination in angiosperms | when pollen reaches the stigma, it germinates, and a pollen tube grows down, carrying the sperm nuclei to the embryo sac; after double fertilization takes place, development of the embryo and endosperm begins |
| what are pollinators | insects, birds, or other animals which transfer pollen between plants of the same species |
| what can block reproduction | mutations in either parent; physical barriers to pollination; |
| what has coevolved with floral morphology | pollinators have coevolved with pollinators |
| how were early seed plants pollinated | passively by the action of the wind |
| how must individual plants of any wind-pollinated species grow | they must grow relatively close to one another for such a system to operate efficiently |
| what has played an important role in the evolutionary success of the group | the spreading of pollen from plant to plant by pollinators visiting flowers of an angiosperm species |
| how were earliest angiosperms and perhaps their ancestors pollinated | they were insect-pollinataed |
| among insect-pollinated angiosperms, what are the most numerous groups pollinated by | bees |
| how do bees find plants | initially locate sources of food by odor, and then orient themselves on flower by its shape, color, and texture |
| describe the flowers that bees charactersitically visit | often blue or yellow; lines or dots that indicate nectaries |
| what are nectaries | often occur within the throats of specialized flowers |
| what can the relationship between bees and flowers result in | can lead to modifications over time in both the flowers and bees; provide both an efficient mechanism for pollination for flowers and a constant source of food for the bees that "specialize" on them |
| how do solitary bees often use flowers | they often use flowers of a particular group of plants almost exclusively as sources of their larval food |
| what is the name of a flower often visited by butterflies | phlox |
| how do flowers visited by butterflies often look | often have flat "landing platform" |
| describe flowers that are visited by moths | they are often white, yellow, or some other pale color; heavily scented; examples are jimsonweed and evening primrose |
| what must plants do to ensure birds will continue to visit them | plants must produce large amounts of nectar because birds will not continue to visit flowers if they do not find enough food to maintain themselves |
| why do flowers that produce large amounts of nectar not have an advantage | they have no advantage in being visited by insects, because an insect could obtain its energy requirement at a single flower and would not cross-pollinate the flower |
| what have flowers adapted to be appealing to insects and birds | evolution of flower color; ultraviolet light is highly visible to insects |
| what pigment is responsible for the colors of many flowers | carotenoids |
| what forms the distinctive color called "bee's purple" | carotenoids reflect both in the yellow range and in the ultraviolet range creating this mixture color |
| what does not stand out as a distinct color to most insects but is a very conspicuous to birds | red |
| what does the color red do for flowers | signals to birds the presence of abundant nectar and makes that nectar as inconspicuous as possible to insects |
| where is red also seen | in fruits that are dispersed by birds |
| what other kinds of animals aid in pollination | bats and small rodents and monkeys |
| where is wind-pollination typically seen | in early seed plants |
| describe flowers of early seed plants that were wind-pollinated | small, greenish, and odorless; their corollas are reduced or absent; grouped together in fairly large numbers and may hang down in tassels that wave about in the wind and shed pollen freely |
| describe wind-pollinated plants | stamen and carpel-containing flowers separated between individuals or physically separated on a single individual |
| what strategy promotes outcrossing in plants that use wind pollination | separation of pollen producing and ovule-bearing flowers; |
| describe how separation of pollen-producing and ovule-bearing flowers allows for more outcrossing | promotes outcrossing since pollen from one flower must land on a different flower for fertilization to have any chance of occuring |
| what is a survival advantage of being wind-pollinated | these species do not depend on the persence of a pollinator for species survival |
| for who is outcrossing highly advantageous for | plants and for eukaryotic organisms |
| describe how most self-pollinating plants reproductive structures look | have small, relatively inconspicuous flowers that shed pollen directly onto the stigma, sometimes even before the bud opens |
| what are the two basic reasons for the frequent occurrence of self-pollinated angiosperms | 1.) self-pollinators do not need to be visited by animals to produce seeds; they can expend less energy on pollinator attractants and can grow in areas where the kinds of insects that might visit them are absent or scarce 2.) self-pollination produces progenies that are more uniform than those that result from outcrossing because meiosis is involved (recombination still takes place); offspring will not be identical to the parent; progenies may contain high proportions of individuals well-adapted to particular habitats |
| what are two strategies to promote outcrossing | to separate the stamens and pistils; another strategy involves self-incompatibility that prevents self-fertilization |
| what are dioecious plants (two houses) | staminate and pistillate flowers may occur on separate plants; produce only ovules or only pollen; rely exclusively on outcrossing |
| describe monoecious plants (one house) | separate male and female flowers may both be produced on the same plant; separation of pistillate and staminate flowers, which may mature at different times, greatly enhances the probability of outcrossing |
| examples of dioecious plants | willows and mulberries |
| examples of monoecious plants | oaks, birches, corn, and pumpkins |
| what are dichogamous plants | when the stamens and pistils are present in each flower of a particular species but these organs reach maturity at different times |
| what is the effect of being dichogamous | separation in time has same effect as if individuals were dioecious; outcrossing rate is increased significantly |
| how are many flowers constructed | so that stamens and stigmas do not come in contact with each other |
| what is the natural tendency in plants that have stamen and stigmas that do not come in contact with each other | for pollen to be transferred to the stigma of another flower, rather than to the stigma of its own flower, thereby promoting outcrossing |
| what does self-incompatibility increase | outcrossing |
| when does self-incompatibility occur | when the pollen and stigma recognize each other as being genetically related, and pollen tube growth is blocked |
| what is self-incompatibility controlled by | the S (self incompatibility) locus |
| what do many alleles at the S locus regulate | recognition responses between pollen and stigma |
| what are the two types of self-incompatibility | gametophytic self-incompatibility and sporophytic self-incompatibility |
| describe gametophytic self-incompatibility | depends on the haploid S locus of the pollen and the diploid S locus of the stigma; if either of the S alleles in the stigma matches the pollen's S allele, pollen tube growth stops before it reaches the embryo sac |
| describe sporophytic self-incompatibility | both S alleles of the pollen parent, not just the S allele of the pollen itself, are important; if the alleles in the stigma match either of the pollen parent's S alleles, the haploid pollen will not germinate |
| what two key developments result from double fertilization | the fertilization of the egg and the formation of a nutrient substance called endosperm that nourishes the embryo |
| describe double fertilization in angiosperms | pollen grain adheres to the stigma and begins to grow a pollen tube that pierces the style; pollen tube grows until it reaches the ovule in the ovary; meanwhile the generative cell within the pollen grain tube cell divides to form two sperm cells; pollen tube reaches the embryo sac in the ovule; entry to embryo sac one of the nuclei flanking the egg cell degenerates and pollen tube enters that cell; tip of pollen tube bursts and releases the two sperm cells; one of the sperm cells fertilizes the egg cell, forming a zygote and the other sperm cell fuses with the two polar nuclei located at the center of the embryo sac forming the triploid primary endosperm nucleus; primary endosperm nucleus eventually develops into the endosperm; after fertilization the embryo develops as its cell divides numerous times; meanwhile protective tissues enclose the embryo resulting in formation of the seed; seed is enclosed in another structure called the fruit |
| what does asexual reproduction result in | genetically identical individuals because only mitotic cell divisions occur |
| where is asexual reproduction used | in agriculture and horticulture |
| what is apomixis asexual reproduction | when the embryos in the seeds may be produced asexually from the parent plant |
| what kind of individuals does apomixis asexual reproduction produce | gives rise to individuals that are genetically identical to their parents |
| describe apomixis asexual reproduction | plants reproduce by cloning diploid cells in the ovule |
| what is the advantage of apomixis asexual reproduction? | gain the advantage of seed dispersal because plants reproduce by cloning diploid cells in the ovule; common in harsh and marginal environments where there is little leeway for variation |
| what is vegetative reproduction | an asexual reproduction; new plant individuals are simply clones from parts of adults |
| what are four forms of vegetative reproduction in plants | runners/stolons, rhizomes, suckers, and adventitious plantlets |
| describe runners/stolons | long, slender stems that grow along the surface of the soil; just beyond each second node, the tip of the runner turns up and becomes thickened which first produces adventitous tissue and then a new shoot |
| describe rhizomes | underground horizontal stems; invade areas near the parent plant and each node can give rise to a new flowering shoot |
| what are corms and bulbs | vertical underground stems |
| what are tubers | stems specialized for storage and reproduction; terminal storage portion of a rhizome |
| describe suckers | the roots of some plants produce these; sprouts which give rise to new plants |
| describe adventitious plantlets | reproductive leaves |
| how can whole plants be cloned | by regenerating plant cells or tissues on nutrient medium with growth hormones (another form of asexual reproduction) |
| true or false: individual cells can give rise to whole plants in culture | true |
| what is protoplast | a plant cell enclosed only by a plasma membrane |
| describe how a single plant cell can produce whole plants | single plant cells are cultured, wall regeneration takes place; cell division follows to form a callus, an undifferentiated mass of cells; once a callus is formed whole plants can be produced in culture |
| what is a callus | an undifferentiated mass of cells |
| why do short-lived plants rarely become woody | there is not enough time for secondary tissues to accumulate |
| what are woody plants | perennial |
| what are perennial plants | continue to grow year after year and may be herbaceous, or woody; able to flower and produce seeds and fruit for an indefinite number of growing seasons |
| what are the majority of vascular plants | perennials |
| true or false: herbaceous perennials rarely experience any secondary growth in their stems | true |
| what does it mean to be deciduous | with all the leaves falling at one particular time of year and the plants remaining bare for a period |
| what does it mean to be evergreen | the leaves dropping throughout the year an the plants never appearing completely bare |
| what are generally either deciduous or evergreen | trees or shrubs |
| what are annual plants | they grow, flower, and form fruits and seeds within one growing season and die when the process is complete |
| how do annuals typically grow | they generally grow rapidly under favorable conditions and in proportion to the availability of water or nutrients |
| describe the death of annual plants | annuals typically die after flowering once; the developing flowers or embryos use hormonal signaling to reallocate nutrients, so the parent plant literally starves to death |
| what is senescence | the process that leads to the death of a plant |
| what are biennial plants | have life cycles that take two years to complete |
| describe the first year of biennial plants | store the products of photosynthesis in underground storage organs |
| describe the second year of biennial plants | flowering stems are produced using energy stored in the underground parts of plants |
| what are examples of wild biennials | evening primrose, queen anne's lace, and mullein |
| true or false: many plants that are considered biennials actually do not flower until they are three or more years of age, but all biennial plants flower only once before they die | true |
| how many times do biennial plants flower before they die | once |
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