Range Science 307
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D. Fruit
Ovary Ovule
The grass fruit is a caryopsis:
E. Cross-section of spikelet:
3. Sexuality of Reproductive Parts
B. Imperfect
Pistillate
Staminate
“Fertile”
“Sterile”
Neuter
Reduced florets (see Harrington, p. 30-31)
Monoecious = Having unisexual spikelets, with both sexes born on the same plant (corn). 31
Dioecious = Having unisexual spikelets, with the sexes born on different plants, the plants then staminate or pistillate (buffalograss, burrograss).
4. The Inflorescence
(See the lab exercise on inflorescences and the article “Describing the Grass Inflorescence” in this study guide.)
Correct: an panicle of spicate, digitate primary branches. Correct: an open panicle of rebranching branches; or, an open rebranching panicle.
Correct: a spicate panicle of weakly developed primary branches, the branches and spikelets appressed to the rachis.
Incorrect: a digitate panicle. Panicles are never digitate in grasses. They may have primary branches, however, that are digitate. The correct description would be: a panicle of digitate branches.
Incorrect: a panicle of spikes. An inflorescence type is never composed of another inflorescence type. The correct description would be: a panicle of spicate primary branches.
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STUDY QUESTIONS
1. Diagram completely a spikelet with 1 floret, one with 2 florets, one without glumes. Label and position all parts correctly.
2. How would you define the grass spikelet? It represents a highly modified ______________________. 3. List the parts of the grass floret.
4. Distinguish between rachis and rachilla, between pedicel and peduncle. 5. Describe the homology between palea and prophyll.
6. Diagram the gynoecium, androecium, and perianth of the typical grass flower. Label and position all parts correctly.
7. The ovule develops into the __________ and the ovary develops into the __________. 8. **This question will be on the first exam**: Define monoecious, as used in grasses. Here is the correct definition (do not use the definition given in Harrington): Monoecious = Having unisexual spikelets, with both sexes borne on the same plant.
9. What is the function of the lodicules? What is their homology? 10. Diagram the grass flower in cross-section (aerial view) with the associated lemma, palea, and rachilla. Label all the parts.
11. Define: plumose dioecious
monoecious reduced
rudimentary or vestigial sterile floret
fertile floret neuter
staminate pistillate
caryopsis achene
membranous hyaline / scarious
indurate cartilaginous
chartaceous 33
12. Diagram a spike, raceme, and panicles of various sorts.
13. Which spikelet part is most apt to be modified? Last to disappear? 14. Which spikelet part is almost always two-nerved?
15. Describe lateral and dorsal compression. 16. Describe 9 ways in which the grass inflorescence may disarticulate (articulate).
17. If only one glume is present, how do you tell which glume it is, the first or the second? 18. Why do grass bracts nearly always have an odd number of nerves?
19. Based on what you now know about the organization of the spikelet, what is incorrect about the diagram below (taken from the study guide from another university)?
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