Flowers and Pollination
What are the four floral whorls, listed from the outside inward?
1. Calyx: sepals, which protect the flower bud. 2. Corolla: petals, which often attract pollinators. 3. Androecium: stamens, the male reproductive structures. 4. Gynoecium: carpels, the female reproductive structures.
What is the difference between gymnosperm and angiosperm seeds?
Gymnosperms produce seeds that are not enclosed within an ovary-derived fruit. Angiosperms produce seeds enclosed within fruits that develop from the ovary.
What two developmental patterns are established during embryogenesis?
Apical–basal polarity establishes the shoot-to-root axis. Radial patterning establishes the organization of tissues from the outside toward the center.
What are the four regions of a growing root, and what does each do?
1. Root cap: protects the growing tip. 2. Zone of cell division: meristematic cells divide by mitosis. 3. Zone of elongation: cells lengthen, extending the root. 4. Zone of maturation/differentiation: cells specialize and root hairs develop.
What do xylem and phloem transport?
Xylem transports water and dissolved mineral ions, mainly from roots toward shoots. Phloem transports sugars, especially sucrose, and other organic solutes from sources to sinks.
Define pollination, and distinguish self-pollination from cross-pollination.
Pollination is the transfer of pollen from an anther to a stigma. Self-pollination occurs within the same flower or plant. Cross-pollination transfers pollen between different plants of the same species. Self-pollination is reliable but reduces genetic diversity; cross-pollination generally increases genetic variation.
Distinguish quiescent seeds, dormant seeds, and vivipary.
Quiescent seeds do not germinate because environmental conditions are unsuitable and can germinate when conditions improve. Dormant seeds remain unable to germinate even under otherwise favorable conditions until dormancy-breaking requirements are met. Vivipary occurs when a seed begins germinating while still attached to the parent plant.
The first zygotic division produces apical and basal cells. What does each primarily contribute to?
The apical cell primarily forms the embryo proper. The basal cell primarily forms the suspensor-->helps position the embryo and transfer nutrients. its uppermost cell can also contribute to the embryo in many plants.
How are vascular bundles arranged in monocot versus eudicot stems?
In a typical herbaceous eudicot stem, vascular bundles form a ring. In a typical monocot stem, bundles are scattered throughout the ground tissue. This arrangement helps distinguish the two in cross section.
What are heartwood and sapwood? What happens when a tree is girdled?
Heartwood is older, generally nonconducting inner xylem that provides structural support.
Sapwood is the younger, conducting outer xylem.
Girdling removes a strip of bark containing phloem and interrupts sugar transport to roots; the roots eventually starve, potentially killing the tree. If severe, girdling can also disrupt other tissues.
What is coevolution, and how do pollination syndromes demonstrate it? Give two examples.
Coevolution occurs when interacting species exert reciprocal selective pressures on one another. Pollination syndromes are combinations of floral traits associated with particular pollinators. Bees are attracted to many blue or yellow flowers with nectar and scent; wind-pollinated plants often have inconspicuous flowers, little or no nectar, and abundant lightweight pollen.
What is imbibition? Compare epigeous and hypogeous germination.
Imbibition is the initial uptake of water by a dry seed. In epigeous germination, the cotyledons are carried above ground, often by hypocotyl elongation. In hypogeous germination, the cotyledons remain below ground.
Name the three primary meristems and the tissues each produces.
Protoderm produces the dermal tissue system, including the epidermis. Ground meristem produces ground tissues, including parenchyma, collenchyma, and sclerenchyma. Procambium produces primary vascular tissues: primary xylem and primary phloem.
Compare primary growth and secondary growth. Which meristems are responsible?
Primary growth increases length through apical meristems and produces primary tissues. Secondary growth increases girth through lateral meristems. Vascular cambium produces secondary xylem inward and secondary phloem outward. Cork cambium produces the periderm, a protective covering that replaces the epidermis in woody organs.
Explain the tension–cohesion mechanism of water transport and the pressure-flow mechanism of phloem transport. I'd recommend drawing it. If this question is on exam, draw it on paper and turn it in with exam.
Tension–cohesion: evaporation from leaves during transpiration creates negative pressure that pulls a continuous column of water upward through xylem. Cohesion between water molecules and adhesion to xylem walls help maintain the column.
Pressure flow: sugars are loaded into phloem at a source, water enters osmotically, and positive pressure drives sap toward sinks, where sugars are unloaded. Both mechanisms operate together to distribute water and nutrients.
Explain protandry and buzz pollination
Protandry=male reproductive structures mature before female structures, reducing self-pollination. In buzz pollination, bees vibrate flowers to release pollen from specialized anthers.
Define heterospory, homospory, microspore, megaspore, and sporophyte dominance.
Heterospory produces two spore types: microspores and megaspores. Homospory produces one spore type, developing into bisexual gametophytes. Microspores develop into male gametophytes; megaspores develop into female gametophytes. Sporophyte dominance means the diploid sporophyte is the large, independent, dominant generation, as in vascular plants.
Put the major eudicot embryo stages in order. How many cotyledons do monocots and eudicots develop?
The major stages are globular → heart → torpedo. The heart stage reflects cotyledon development. Monocots develop one cotyledon, eudicots develop two. The hypocotyl is the embryonic axis below the cotyledons, the radicle is the embryonic root.
Define pneumatophores, buttress roots, haustoria, lenticels, and mycorrhizae. Explain the benefit of each.
Pneumatophores are aerial roots that help oxygen reach roots in waterlogged soils.
Buttress roots stabilize large trees in shallow soils.
Haustoria penetrate host tissues to obtain water and nutrients in parasitic plants.
Lenticels are openings in woody bark that allow gas exchange.
Mycorrhizae are mutualistic root–fungus associations: fungi improve water and mineral uptake, while plants provide carbohydrates.
Explain the Janzen–Connell hypothesis and how it can promote plant diversity.
Seeds and seedlings close to a parent plant may experience greater attack from specialized herbivores or pathogens, or stronger competition. Seed survival often increases farther from the parent, although the pattern varies by species and environment. This distance- or density-dependent mortality can prevent one species from dominating and help maintain plant diversity. Seed dispersal by animals, wind, or water can move seeds away from parent plants.
Explain how male and female gametophytes develop in flowering plants, and describe how pollination leads to double fertilization.
In the anther, meiosis produces haploid microspores that develop into pollen grains containing two sperm. In the ovule, meiosis produces megaspores, one of which develops into the embryo sac. One sperm fertilizes the egg to form a diploid zygote; the other fuses with two polar nuclei to form triploid endosperm. This is called double fertilization.
Identify five evolutionary advantages or innovations associated with pollen and seeds that helped plants reproduce on land. Explain why they mattered.
Strong answers: (1) Pollen transports the male gametophyte without requiring free-standing water for sperm delivery. (2) A pollen wall protects the male gametophyte against desiccation. (3) Pollen tubes deliver sperm directly toward the egg. (4) Seeds protect the embryo with a seed coat. (5) Seeds store nutrients for embryonic development.
Explain how apical–basal polarity and the three primary meristems build a functional seedling. Include primary and secondary tissues and at least two examples.
Apical–basal polarity- establishes the shoot and root ends, organizing body plan. The protoderm--> epidermis. ground meristem forms ground tissues. procambium forms primary xylem and phloem. These primary tissues support protection, photosynthesis, storage, and transport.
Ex. leaf chlorenchyma carries out photosynthesis, while root xylem transports absorbed water. Later during secondary growth, vascular cambium forms secondary xylem and phloem, and cork cambium produces periderm. These lateral meristems increase girth and replace the original protective surface in woody organs.
DRAWING CHALLENGE YAY: Draw and fully label cross sections of a monocot root, eudicot root, monocot stem, and eudicot stem. Explain how to distinguish each.
MONOCOT ROOT: label epidermis, cortex, endodermis, pericycle, xylem, and phloem; vascular tissue typically surrounds a central pith, with numerous xylem poles.
EUDICOT ROOT: label the same tissues; xylem commonly forms a central star or X, with phloem between the arms and little or no central pith.
MONOCOT STEM: label epidermis, ground tissue, and scattered vascular bundles; within bundles, label xylem and phloem.
EUDICOT STEM: label epidermis, cortex/ground tissue, and vascular bundles arranged in a ring; label xylem toward the inside and phloem toward the outside. Add the vascular cambium between xylem and phloem in a typical eudicot bundle. Remember: these are typical patterns, and real species may vary.
A woody plant grows taller each year and its trunk thickens. Trace water from soil to leaves and sugars from leaves to storage roots. Identify the tissues and meristems involved.
LONG ANSWER, GOOD TO KNOW: Water enters root hairs by osmosis and moves through the epidermis and cortex toward the endodermis. The Casparian strip in the endodermis regulates entry into the stele; water then passes the pericycle and enters xylem. Transpiration from leaves creates tension that pulls water upward through xylem by the cohesion–tension mechanism. Leaves produce sugars by photosynthesis. Sucrose is loaded into phloem, water enters osmotically, and pressure flow moves sugars toward sink tissues such as storage roots. Apical meristems increase length and form primary tissues. Vascular cambium adds secondary xylem inward and secondary phloem outward; cork cambium forms protective periderm. The secondary xylem builds wood, while functional phloem distributes sugars to storage tissues.
SHORT ANSWER: Xylem moves water upward through transpiration, while phloem transports sugar from sources to sinks.