well one of the factors to help plants grow is the light. And you really need at least 2 Watts per gallon. That bit should be very easy for you to work out.
Add some
reflectors and they double your watts per gallon.
But then you need to have the right kind of tubes / light for plants.
As per the last link I gave you, here are some examples of tubes for a planted tank - your lfs should stock some of these though unlikely the whole range :
Dennerle - Special-Plant 3000K Warm, yellow/orange
Hagen - Life-Glo 6700K Bright, cool white
Arcadia - Freshwater Lamp 7500K Cool white/green
Zoo Med - Tropic-Sun 5500K Warm white
Zoo Med - Ultra-Sun 6500K Bright Cool white
Interpet - Triton/Triplus 8300K Bright white/purple
Interpet - Daylight Plus 6500K Cool white