Irregardless of Final Phase's interpretation of photosynthesis ("Photo synthesis" sic), any plant is carrying out a lot of activity during the dark period of a 24 hour cycle.
"It can take in a watering before it goes to sleep and it will swell... I think it's best to water when at the beginning of a light period."
WOW Final Phase - My plants do not ever "go to sleep, nor do they "Swell". And why do you "Think" it's best to water at the beginning of a light period.
Oh yeah, the internet.