Cactus / grafted agavoides

I sowed seeds collected from my plants on 23/ 09/2011.
One dozen of very young seedlings were grafted on Pereskiopsis stocks.
The photo is one of them, 2 years old.
Since daylight time has been shorter, the plant lifts several buds up but they may not be opened because the temperature of outside is very high, 41 'C.
Tubercles of agavoides are very short when it was grafted.