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प्रश्न
Describe the important characteristics of gymnosperms.
उत्तर
Important features of gymnosperms:
- The term gymnosperm refers to plants with naked seeds (gymnos – naked, sperma – seeds), i.e., the seeds of these plants are not enclosed in fruits.
- The plant-body ranges from medium to tall trees and shrubs. The giant redwood tree Sequoia is one of the tallest trees in the world.
- The root system consists of tap roots. The coralloid roots present in Cycas are associated with nitrogen-fixing cyanobacteria.
- The stem can be branched (as in Pinus and Cedrus) or unbranched (as in Cycas).
- The leaves can be simple (as in Pinus) or compound (pinnate in Cycas). The leaves are needle-like, with a thick cuticle and sunken stomata. These help in preventing water loss.
- Gymnosperms are heterosporous. They bear two kinds of spores – microspores and megaspores.
- Flowers are absent. The microsporophylls and megasporophylls are arranged to form coGnetummpact male and female cones.
- Pollination occurs mostly through wind and pollen grains reach the pollen chamber of the ovule through the micropyle.
- The male and female gametophytes are dependent on the sporophyte.
- The seeds contain haploid endosperms and remain uncovered.
APPEARS IN
संबंधित प्रश्न
Write a note on the economic importance of gymnosperms.
Endosperm in gymnosperm is formed ______.
What do you infer from the term pycnoxylic?
Mention two characters shared by gymnosperms and angiosperms.
Read the following five statements (i to v) and select the option with all correct statements:
- Mosses and lichens are the first organisms to colonise a bare rock.
- Selaginella is a homosporous pteridophyte.
- Coralloid roots in Cycas have V AM.
- Main plant body in bryophytes is gametophytic, whereas in pteridophytes it is sporophytic.
- In gymnosperms, male and female gametophytes are present within sporangia located on sporophyte.
In gymnosperms, megaspore mother cell divides meiotically to form four megaspores. Out of four megaspores, one develops into a multicellular structure termed as : ·
Gymnosperms are called naked seeded plants due to the absence of
Which of the following is not found in gymnosperms?
Plants of this group are diploid and well adapted to extreme conditions. They grow bearing sporophylls in compact structures called cones. The group in reference is ______.
The giant Redwood tree (Sequoia sempervirens) is a/an ______.
Each plant or group of plants has some phylogenetic significance in relation to evolution: Cycas, one of the few living members of gymnosperms is called as the ‘relic of past’. Can you establish a phylogenetic relationship of Cycas with any other group of plants that justifies the above statement?
In which plant will you look for mycorrhiza and corolloid roots? Also explain what these terms mean.
Lichen is usually cited as an example of ‘symbiosis’ in plants where an algal and a fungal species live together for their mutual benefit. Which of the following will happen if algal and fungal partners are separated from each other?
- Both will survive and grow normally and independent from each other.
- Both will die
- Algal component will survive while the fungal component will die.
- Fungal component will survive while algal partner will die.
Based on your answer how do you justify this association as symbiosis.
