HardBiologyHigh School (11–12)Diversity of Living Organisms › Bryophytes and PteridophytesConceptualBoard Exam
Nisha cuts a moss plant just below the foot of its sporophyte, so that the sporophyte (seta and…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Nisha cuts a moss plant just below the foot of its sporophyte, so that the sporophyte (seta and capsule) is separated from the leafy shoot. She keeps both parts on damp soil in the light. A week later the leafy shoot is still green, but the sporophyte has dried up. (a) Explain the result. (b) Is the sporophyte haploid or diploid? (c) What would the capsule have made if it had matured?
Need a reminder? The key ideaShow
Bryophytes (liverworts and mosses) live in damp places and need water for fertilisation. The main plant body is the haploid gametophyte, held by rhizoids, with no vascular tissue. Antheridia make biflagellate antherozoids; archegonia make one egg. The zygote grows into a sporophyte (foot, seta, capsule) that depends on the gametophyte and makes spores by meiosis. Liverworts make gemmae in gemma cups; mosses grow from a protonema. Sphagnum holds much water and forms peat.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. Food. In a moss, the leafy shoot is the green gametophyte. It makes food and lives on its own. The sporophyte is not free-living: through its foot it takes food and water from the gametophyte. Cut off, it starves and dries up.
Step 2. Its chromosomes. The sporophyte grows from the zygote, so it is diploid.
Step 3. The capsule. Some of its cells would have divided by meiosis to make haploid spores, which grow into new protonemata.
Answer: (a) the sporophyte depends on the gametophyte for food and water, so it died when cut off; (b) diploid; (c) haploid spores, by meiosis.
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