its in the datasheet but you might not understand all of it if you dont read a bit into eletronics.
the thing is, leds are not manufactured for the aquarium industry, they are just made, mostly for flashlights now as far as i know, and trying to break into house lighting, but the aquarium trade is rather small they would not cater to us. if keno or myself get readings im sure they will be some of the first led for planted tank readings we've seen.
the datasheet does have information in the form of lumens, but only the total emission, not the lux at certian distances, and especially not through water. i would say leds can definateley grow plants, and with no need for dimming and fewer number of leds, the build could cost half of what a saltwater build for the same size would cost
sorry keno, didnt mean to hijack, ill cut it out =)