Make observations of pine pollen under the microscope. (Use a prepared slide of
ID: 218008 • Letter: M
Question
Make observations of pine pollen under the microscope. (Use a prepared slide of pine pollen, if fresh pollen is not available for a wet mount). Notice the unusual structure of the pollen grains. 4. You probably noticed that pollen grains have wings on them. What is the purpose of the wings? Gymnosperms, like the conifers, are characterized by having wind-dispersed pollen. How was this method of pollen dispersal an important evolutionary adaptation for these plants? A major evolutionary trend in higher terrestrial plants is the reduction in size of the male and female gametophytes. Describe how the gametophytes of conifers follow this trend.
Explanation / Answer
a. Winged pollen grains are found only in extinct angiosperms. They are found in few living species of gymnosperms such as pinus. These pollen winds enable dispersal of pollen by the wind to longer distances.
b. Winged pollen grains enabled gymnosperms to enter new terrestrial habitats with dry climate. It is also helpful in increasing the genetic diversity of a species.
c. There is a gradual increase in the duration of sporophytic life stage and a gradual decrease in the gametophytic life stage from algae to angiosperms.
Algae and bryophytes = Dominant gametophyte and reduced sporophyte
Pteridophyte = Equal duration of sporophyte and gametophyte
Gymnosperms and angiosperms = Dominant sporophyte and reduced gametophyte
Conifers belong to gymnosperms. They exhibit dominant sporophytic stage. Gametophytic stage is only present in the gametes.
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