Study "Plants (3) - Bryophytes", a flashcard deck on FORKSAI.
Define bryophytes and explain the primary reason for their limited size and preference for moist environments.
Bryophytes are nonvascular land plants, meaning they lack specialized tissues like xylem for water transport. This absence, along with their inability to produce lignin, restricts their height to only a few centimeters and necessitates moist environments for survival and reproduction.
How do rhizoids in bryophytes differ from true roots found in vascular plants?
Rhizoids in bryophytes serve primarily to anchor the plant to the soil but do not absorb water or nutrients. In contrast, true roots in vascular plants contain xylem and phloem, allowing them to efficiently absorb and transport water and nutrients throughout the plant.
Explain the significance of the gametophyte being the dominant, visible plant in bryophytes.
The dominant, visible plant in bryophytes is the haploid gametophyte, which is responsible for photosynthesis and overall plant structure. The sporophyte, which produces spores, is typically smaller, short-lived, and nutritionally dependent on the gametophyte for its development and survival.
In what specific way does the reproductive strategy of bryophytes necessitate the presence of moisture?
Bryophytes require moisture for sperm transfer during reproduction. Sperm produced in the antheridia are flagellated and must swim through a film of water to reach the egg located within the archegonium, enabling fertilization.
Distinguish between thalloid liverworts and leafy liverworts based on their gametophyte structure.
Thalloid liverworts have a gametophyte composed of a flattened, irregular body of green tissue called a thallus, which does not form distinct leaves or stems. Leafy liverworts, however, have a gametophyte that consists of an axis with leaf-like structures, typically one cell thick.
Describe the role of gemma cups and gemmae in Marchantia.
Gemma cups are structures found on the thallus of Marchantia that produce gemmae. Gemmae are small, disc-shaped multicellular bodies that are dispersed by raindrops and can develop into new, genetically identical gametophytes, facilitating asexual reproduction.
How does the sporophyte of Marchantia obtain its nutrition, and what structures comprise it?
The sporophyte of Marchantia is nutritionally dependent on the gametophyte, anchoring to it via a foot. The mature sporophyte consists of three main structures: the foot, which attaches it to the gametophyte; the seta, a stalk that elongates; and the capsule (sporangium), where spores are produced by meiosis.
What is the primary function of the capsule (sporangium) in a bryophyte sporophyte?
The primary function of the capsule (sporangium) in a bryophyte sporophyte is to produce spores through the process of meiosis. These spores are then dispersed, and under suitable conditions, they can germinate and develop into new haploid gametophytes.
Explain why bryophytes are considered 'low growing' and cannot achieve the height of vascular plants.
Bryophytes are low growing because they lack lignin, a rigid polymer that provides structural support in vascular plants, and specialized vascular tissues (xylem) for efficient water transport. Without these, they cannot support tall structures or move water against gravity over significant distances.
What does it mean for Marchantia to be 'dioecious,' and how does this impact its reproduction?
Marchantia is dioecious, meaning it has separate male and female plants. This implies that for sexual reproduction to occur, sperm from a male plant must be transferred to an egg on a female plant, often facilitated by external agents like raindrops splashing sperm.