i need help! understanding

can any one please help me, i was reading an article about advantages and disadvantages of T5 and LED technology but what i fail to understand is this lm/W rating there talking about , for example LED lamp was only
78.5 lm/W. please help

First link on a google search: http://en.wikipedia.org/wiki/Luminous_efficacy

Someone correct me if im wrong, but lumens isnt an important factor when using a lamp for growing purposes.
Its only importent when you are using your light for illuminating a room.

The lm/W just tells you how much light from the visible spectre you will get and not necessarily the spectres that are important to plants.

When looking for grow light it is the spectres around 450nm (blue) and around 660nm (red) that are the important ones, because it is the light the plant uses for growing.