Bryophyte Study Guide

📖 Core Concepts Bryophytes: Non‑vascular land plants (liverworts, hornworts, mosses). Dominant life‑stage: The multicellular haploid gametophyte is the conspicuous phase; the diploid sporophyte is dependent on the gametophyte. Sporophyte: Unbranched, single sporangium (capsule) on a seta; produces haploid spores by meiosis. Sexuality terms Monoicous = both antheridia (male) & archegonia (female) on one gametophyte. Dioicous = male and female organs on separate gametophytes. Monoecious/dioecious refer to seed‑plant sporophytes – not bryophytes. Phylogeny: Modern molecular data support a monophyletic Bryophyta (all three groups share loss of lignified vascular tissue and a simple sporophyte). Habitat: Small, moist‑dependent plants; can colonize bare rock, soil, or substrates where vascular roots are absent. 📌 Must Remember Dominant stage: Haploid gametophyte (✓). Sporophyte traits: Diploid, unbranched, 1 sporangium, seta + capsule (✓). Sexual systems: Monoicous = same gametophyte; Dioicous = separate gametophytes (✓). Classification: Marchantiophyta = liverworts Bryophyta = mosses Anthocerotophyta = hornworts (✓). Key distinction from vascular plants: No true lignified vascular tissue; water conducts through specialized cells only. Spore dispersal: Wind‑borne haploid spores released after capsule dehiscence (✓). 🔄 Key Processes Sexual reproduction Male antheridia release flagellated sperm → swim in water film → fertilize egg in archegonia. Zygote → diploid sporophyte embryo develops inside archegonia. Sporophyte development Embryo forms foot, seta, and capsule. Basal meristem in seta pushes capsule upward. Meiosis in capsule → haploid spores. Spore dispersal Capsule opens → wind carries spores → germinate into new gametophytes. Asexual propagation (optional) Fragmentation of thallus or stem, or production of gemmae (tiny propagules). 🔍 Key Comparisons Monoicous vs Dioicous Monoicous: both sex organs on one plant → higher self‑fertilization chance. Dioicous: separate male & female plants → obligate outcrossing. Bryophyte vs Vascular Plant Sporophyte Bryophyte: single sporangium, unbranched, nutritionally dependent. Vascular: multiple sporangia, branched, independent photosynthetic tissues. Moss vs Liverwort vs Hornwort Gametophyte Moss: leafy, often many sporophytes per plant. Liverwort: thalloid or leafy, may have distinct gametangiophores. Hornwort: thalloid, often hosts cyanobacterial symbionts. ⚠️ Common Misunderstandings “Bryophytes are non‑vascular” → “they have no water transport.” They lack lignified vascular tissue but may have specialized water‑conducting cells. Confusing monoicous/dioicous with monoecious/dioecious. The latter apply to seed‑plant sporophytes, not to bryophyte gametophytes. Assuming all bryophytes need saturated water. They need a thin water film for sperm motility, but many tolerate periods of dryness thanks to cuticle and poikilohydry. 🧠 Mental Models / Intuition “One‑spore‑one‑capsule” model: Every capsule is a single‑sporangium, diploid organ that only produces spores—think of it as a miniature mushroom that cannot feed itself. “Gametophyte‑centric” view: Treat the visible plant you see as the haploid stage; the sporophyte is just a “fruit” hanging off it. 🚩 Exceptions & Edge Cases Autoicous, Paroicous, Synoicous arrangements: All are forms of monoicous sexuality, differing in spatial arrangement of organs on the same gametophyte. Some mosses produce multiple sporophytes per gametophyte – not all mosses follow the “one‑capsule per plant” rule. 📍 When to Use Which Identify a bryophyte group Look at gametophyte morphology (thalloid vs leafy) → liverwort vs moss vs hornwort. Check sporophyte traits: presence of a seta, capsule shape, and whether a basal meristem is evident. Determine sexuality Find both antheridia & archegonia on the same plant → monoicous. Find them on separate plants → dioicous. Apply phylogenetic evidence Use molecular markers (amino‑acid, nuclear, chloroplast genes) when asked about monophyly vs paraphyly. 👀 Patterns to Recognize Single sporangium + unbranched sporophyte → always a bryophyte (vs polysporangiophytes). Flagellated sperm + water film requirement → indicates a bryophyte reproductive strategy. Cuticle + absence of lignin → typical of early‑diverging land plants. 🗂️ Exam Traps Option that says “Bryophytes have true xylem/phloem.” – Wrong; they lack lignified vascular tissue. Choice describing “dioecious” in bryophytes – Misleads; correct term is dioicous (gametophyte level). Statement that all bryophytes are obligate aquatic. – Incorrect; they can survive on rocks and soils with only brief water films. Answer claiming multiple sporangia per sporophyte in bryophytes. – Only polysporangiophytes have that; bryophyte sporophytes bear a single sporangium. --- Use this guide for a quick, high‑yield review before your exam – focus on the bolded keywords and the contrast tables to lock the concepts in place.