Here, the form is restricted by для, which always requires the Genitive. Each preposition has its own case requirements: some only want one case regardless of the meaning, some can use two cases depending on the meaning. Let me illustrate this for с and на:
- с тарелки = from/off the plate / с тарелкой = with the plate
- на тарелке = on the plate (location) / на тарелку = onto the plate (direction)
Whenever you have a situation like this, you do not have much choice, really.
нет + noun ("no something") requires the Genitive.
Now, here is the list of all forms тарелка can have:
It should be fairly clear from this table which form works.
Note how тарелки is the Genitive singular and the Nominative plural. This discrepancy between the cases means that тарелки is singular and plural in different expressions , not unlike these English sentences:
- I removed my boots. ("boots" is a noun in the plural)
- My PC boots extremely fast. ("boots" is a verb, 3rd person singular)
A newbie might also be confused how "-s" means both singular and plural in English. However, this causes no confusion for the most part: English has a rather rigid word order, which makes it easy to tell verbs and nouns apart.
Same here: you would expect the Genitive in "there is no" structure, so any form нет modifies should be interpreted as the Genitive (otherwise they do not stick together):
- Дома нет таблеток
- У нас нет еды.
- У нас нет сыров.
- У учителей нет столов.
- В здании нет вентиляции.
The only nouns that have the same Nominative plural and Genitive plural are indeclinable loanwords (e.g., радио, пони, кенгуру, пюре, пальто etc.)
We don't have a plate for the rice. ‧ A dining menu entree calls for rice to be presented on a plate. A bowl, tray or some other serving dish may have to substitute for the plated rice presentation because the food service providers,
"don't have a plate for the rice" ‧
Additionally, they, "don't have a punch bowl for the punch" ‧ so dispensing the punch from pitchers or creatively, using hollowed out halved watermelons serve as substitute punch bowls.
Here рис is in the genitive because of the preposition для, which always takes the genitive. So the sentence is a plate FOR the rice (because of для), not a plate OF rice (which is what the genitive риса without для would mean). I hope this helps. I'm not entirely sure I understood your question.
нет тарелки (gen sing) : referring to one single plate ? Would it be нет тарелок (gen plur, according to Shady) or тарелк (according to BsTMQ ) if we meant we didn't have plates (one for each of us) ? I always used gen sing so far, because DL didn't address gen plur yet, but at this point конфет (gen plur) has been introduced...