Gymnosperms Plant King. Flashcards
What does ‘gymnosperm’ mean?
‘Gymnosperm’ means ‘naked seeds.’ It refers to plants where the ovules and seeds are not enclosed by an ovary wall and remain exposed.
What are the types of plants included in gymnosperms?
Gymnosperms include medium-sized trees, tall trees, and shrubs. An example is the giant redwood tree Sequoia, one of the tallest tree species.
What type of roots do gymnosperms have?
Gymnosperms have tap roots. Some, like Pinus, have fungal associations (mycorrhiza), while others, like Cycas, have coralloid roots associated with nitrogen-fixing cyanobacteria.
How do stems differ in gymnosperms?
Stems in gymnosperms can be unbranched (Cycas) or branched (Pinus, Cedrus).
How are the leaves of gymnosperms adapted to their environment?
Gymnosperm leaves are adapted to withstand extreme temperatures, humidity, and wind. For example, conifers have needle-like leaves with a thick cuticle and sunken stomata to reduce water loss.
What type of spores do gymnosperms produce?
Gymnosperms are heterosporous (micro and macrospores), producing haploid microspores and megaspores.
What are strobili in gymnosperms?
Strobili (cones) are structures where sporophylls bearing sporangia are arranged spirally. Male cones are called microsporangiate, and female cones are called macrosporangiate.
How does the male gametophyte develop in gymnosperms?
The male gametophyte develops from microspores within the microsporangia, forming a pollen grain. It is highly reduced and limited to a few cells.
What is the female gametophyte’s development process in gymnosperms?
The megaspore mother cell undergoes meiosis to form four megaspores. One megaspore develops into a multicellular female gametophyte, which bears archegonia and remains within the megasporangium.
How does fertilization occur in gymnosperms?
Pollen grains are released, carried by air currents, and come in contact with ovules. The pollen tube grows toward the archegonia, discharges male gametes, and fertilization occurs.
How are seeds formed in gymnosperms?
After fertilization, the zygote develops into an embryo, and the ovules develop into seeds. These seeds remain naked (uncovered).
How do gymnosperms differ from bryophytes and pteridophytes?
In gymnosperms, the male and female gametophytes are not free-living. They remain within the sporangia on the sporophyte.