This lesson introduces the defining features of gymnosperms and follows the reproductive cycle of a pine, a familiar conifer. Understanding this cycle shows how seed plants reproduce without enclosing their seeds in fruits.
Gymnosperms are seed plants whose seeds are not enclosed within an ovary. The word means “naked seeds.” In many species, modified leaves called sporophylls partly shelter the seeds. Sporophylls may be arranged around a central stalk in a structure called a strobilus; pine cones are familiar examples. The protective layer of sporophyte tissue surrounding the megasporangium, and later the embryo, is the integument.
All flashcards
What is a gymnosperm?
A seed plant whose seeds are not enclosed within an ovary; the name means “naked seeds.”
What are heterospory and its two spore types?
Heterospory is the production of two kinds of spores: microspores, which give rise to male gametophytes, and megaspores, which give rise to female gametophytes.
How do monoecious and dioecious plants differ?
A monoecious plant bears male and female reproductive structures on the same plant. A dioecious species has male and female structures on separate plants.
What happens during pollination in a pine?
Pollination is the initiation of pollen-tube growth. Fertilization occurs later, when a sperm nucleus fuses with an egg nucleus.
What are the three generations of tissue in a pine seed?
The seed coat comes from the parent sporophyte, nutritive tissue comes from the female gametophyte, and the embryo is the developing next sporophyte.
Quiz questions
What distinguishes gymnosperm seeds from seeds enclosed in fruits?Answer: Gymnosperm seeds are not enclosed within an ovary.
What is the main function of tracheids in gymnosperm vascular tissue?Answer: They transport water and solutes through the plant.
Why is a pine described as monoecious?Answer: One plant bears both male and female reproductive structures.
How does a male gametophyte develop in a pine?Answer: A microsporocyte undergoes meiosis, and its microspores develop into pollen grains.
Which tissues are typically present in a mature pine seed?Answer: A sporophyte-derived seed coat, nutritive female gametophyte tissue, and an embryo.
Based on Biology 2e by Mary Ann Clark, Matthew Douglas, Jung Choi (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.