Plant Biology - Bryophytes—The Non‐Vascular Plants - Quick Guides

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Study GuidePlant Biology–Bryophytes—The Non‐Vascular Plants1. A Typical Bryophyte Life CycleEven though mosses, liverworts, and hornworts look different,their life cycles follow the samebasic pattern. The diagram above shows a moss life cycle, which represents bryophytes in general.1.1Alternation of Generations: The Big IdeaBryophytes showalternation of generations. This means they have two main stages in their lifecycle:•Gametophyte (haploid, 1n)→ produces gametes (sperm and egg)•Sporophyte (diploid, 2n)→ produces sporesIn bryophytes, thegametophyte is the dominant, green, and independent plantyou usually see.

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Study Guide1.2 From Spores to Protonema(Refer to the upper-left part of the image)•The life cycle begins withhaploid spores (1n).•Each spore can grow into a thin, green, thread-like structure called aprotonema.•The protonema looks like algae and spreads over the surface.•In many mosses, protonemata formdense green matswith rhizoids and upright filaments.•Under suitable conditions (likered light and kinetin), cells of the protonema developbuds.These buds grow intoleafy shoots, which becomemature gametophytes.1.3 Gametophyte: The Main Plant(Refer to the central upper part of the image)•The mature gametophyte isphotosynthetic and independent.•It produces special reproductive structures calledgametangia.There are two types:•Antheridia (male)→ produce sperm•Archegonia (female)→ produce eggsThese structures may be found:•On thesame plant, or•Ondifferent plantsBoth antheridia and archegonia have aprotective sterile outer layer, which helps protect thegametes. This feature is an important evolutionary step compared to algae.

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Study Guide1.4. Fertilization Needs Water(Refer to the right side of the image)•Whenrain or dewis present, mature sperm are released from antheridia.•The sperm arebiflagellate and motile, meaning they can swim.•They swim through the thin film of water to reach the archegonium.•One sperm fuses with the egg → this process is calledfertilization.This type of reproduction is calledoogamy, where:•The egg is large and non-motile•The sperm is small and motileImportant point:Bryophytesrequire external water for fertilization, unlike higher plants wheresperm travel through pollen tubes.1.5Zygote and Embryo Formation(Refer to the lower-right part of the image)•Fertilization forms adiploid zygote (2n).•The zygote stays inside the archegonium.•It divides bymitosisto form amulticellular embryo.•This embryo develops into thesporophyte.The gametophyte supplies food to the developing sporophyte. This nourishment is calledmatrotrophy.•No plasmodesmata connect the two generations.•Nutrients move along thecell walls (apoplastic movement).

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Study Guide1.6Structure of the Sporophyte(Refer to the lower-left and central parts of the image)In mosses and liverworts, the mature sporophyte has three parts:•Foot→ anchors the sporophyte to the gametophyte•Seta→ stalk that lifts the capsule•Capsule (sporangium)→ produces sporesIn mosses:•A protective cap called thecalyptracovers the developing capsule.•The capsule has:oOperculum(lid)oPeristome teeththat help in controlled spore release•Inside the capsule, sterile cells calledelatersrespond to moisture.oThey twist and untwist as they absorb and lose water.oThis movement helps push spores out into the air.1.7Spore Formation and Release(Refer to the capsule region in the image)•Inside the capsule,spore mother cells undergo meiosis.•This produceshaploid spores (1n).•Spores are released and dispersed by wind.•When they land in a suitable place, the cycle begins again.1.8Special Case: Hornwort Sporophyte•In hornworts, the sporophyte is:oLong, green, and cylindricaloPhotosyntheticoProvided withstomata

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