Today we will discuss about the Gymnosperm.
Basically, Gymnosperms are eukaryotic plants, which have naked seed and fertilization takes place after one year of fertilization.
- They are eukaryotic in nature
- They are autotrophic
- Roots,stem and leaf are distinct
- Woody stem and xylem are present
- Naked seeds are present
- Spiny leaves are present
- Fertilisation takes place after one year of pollination
- Male cone and female cone are present
- They are evergreen and perennial
- Eg. Pinus and Cycas, etc.
1. Name one gymnosperm where xylem vessels and companion cells are present. (1)
2. Differentiate between bract scale and ovuliferous scale. (2)
|Bract scale||Ovuliferous scale|
|1. They are located at the base of the microsporophyll.
2. They have a membranous structure.
3. They protect the base of the megasporophyll and provide their attachment with the axis.
|1. They are the upper lateral projections of the megasporophyll.
2. They have a more woody structure.
3. They provide support and protection to the ovules.
- Differentiate between endosperm of gymnosperm and endosperm of angiosperm. (2)
|Endosperm of gymnosperm||Endosperm of angiosperm|
|1. It is haploid in nature.
2. It is formed by the free division of the haploid megaspore nucleus.3. It is a pre-fertilization development.
|1. It is triploid in nature.
2. It is formed by the fusion of the second male gamete with the diploid definitive nucleus.
3. It is post fertilization development formed as a result of double fertilization.
- State two diagnostic features of Pinus leaf. (2)
The leaves of Pinus is needle shaped with undifferentiated mesophyll tissue. They either triangular or semi-circular in outline.
5. What is amber?
Ans. The fossilized resin of the extinct plant Pinitis succinifera is called amber, which is important in jewellery.
- Name four Indian species of Pinus. (2)
Ans. Pinus gerardiana, Pinus wallichiana, Pinus armandi and Pinus roxburghii.
- Name a gymnosperm that produces edible oil. (1)
Ans. Gnetum ula
8. Name a living fossil under Gymnosperm. (1)
Ans. Ginkgo biloba
9. What is polyembyony? What are its various types? (1+1)Ans. The phenomenon by which more than one functional embryo is formed within the seed is called polyembryony. It is of two types:
a) Adventitive polyembryony: There are fusion of additional eggs, arising fro nucellar cells of the megaspore by male gametes.
b) Cleavage polyembryony: In cleavage polyembryony, the embryo undergoes complete cleavage to produce more embryos.
10. What is pycnoxylic wood? b) What is perisperm? (1+1)
a) The wood of Pinus is compact and devoid of xylem parenchyma elements and is called pycnoxylic wood.
b) It is the nutritive tissue surrounding the embryo.
11. What are the fern characters of Pinus? (2)
Ans. The fern characters of Pinus:
a) Presence of scale leaves.
b) Presence of archegonium without neck canal cells.
c) The xylem vessels are absent.
d) Presence of tapetum in the microsporangium.
12. What is shower of sulphur? (2)
Ans. The longitudinal dehiscence of the microsporangia produce the large number of yellow microspores or pollen grains, which cover the lower part of the pine tree including the female cones and is called shower of sulphur.
13. What do you mean by mycorrhizal root? (2)
Ans. The ectotrophic mycorrhizal fungal colony develops a symbiotic association with the Pinus roots. The fungal colony gets shelter in the plant root, while the fungal mycelia procure nourishment from the soil and helps in the plant growth.
14. Enumerate the structure of microsporophyll? (2)
Ans. Microsporophyll: Each microsporophyll shows the following structures.
i) It consists of a short stalk and an expanded upper portion with a slightly bent upward apex (apophysis).
ii) Two sac-like microsporangia are borne on the lower (abaxial surface) of the expanded leafy portion.
15. Enumerate the structure of megasporophyll? (2)
Ans. Each megasporophyll shows the following structures.
i) The megasporophyll consists of a short-stalked, triangular expanded structure called ovuliferous scale and a thin, membranous structure at the base called bract scale.
ii) The bract scales remain at the base of the ovuliferous scale and have the supply of vascular traces.
iii) The ovuliferous scale consists of a short stalk and an upper expanded portion called apophysis
iv) Each ovuliferous scale bears two anatropous megasporangia or ovule on the dorsal surface near the base.
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