Connect the ground wire to the metal box.
The green wire on the light fixture is a ground wire. If there is no ground wire in the conduit, the green wire should be attached to the metal box with a screw.
Connect the ground wire in wall to the base of fixture
If you are talking about the lamp then the answer is no. If you are talking about the fluorescent fixture, it should be. It is the fixture grounding that helps the tube to ignite. because of the close proximity to the metal of the fixture. There are many occasions when the fixture will not operate, but as soon as the ground is connected the fixture operates fine.
If you're asking whether you have to connect the fixture ground to the house ground, you do. The idea is to connect any exposed portion of a metal fixture to ground, keeping anything you would be able to touch from having a hazardous potential on it. The way to do this is to connect the fixture ground (which is connected to the metal chassis) to the building ground (which comes from your electrical panel).
Normally the fixtures come with a grounding screw that you attach the grounding wire to. If the box you attaching the fixture to is metal and there is no grounding wire present then the grounded conduit should ground you fixture.
I always connect the ground wire to the box. However, if there is no real ground wire running back to the panel it really does you no good. The NEC requires that you rewire the circuit with the proper conductors. Remember that the ground is for your protection. Without a proper ground, you run the risk of injury or death if the fixture wiring fails.
The bare copper wire is a ground wire. if your old electrical system only has black and white, then you don't have a ground wire to hook the new fixture's ground to. Safest bet is to run a ground wire to that junction box (or hire an electrician to do that). If the box in the ceiling (I'm assuming its a ceiling fixture) is metal, the home's electrical system ground wire may be attached to the metal box itself. If that's the case, you simply need to attach your new fixture's ground wire (the bare copper one) to the metal box. If in doubt -- have an electrician look at it.
If the fluorescent lighting ballast is attached to a metal lighting fixture the grounding occurs through the metal of the fixture and the screw that holds the ballast in place. Other wise you need to add a gounding clamp or a grounding pig tail to the metal of the ballast. This would only be done in custom installations.
Any fixture containing metal other than the conductors should be grounded. It ensures the proper operation of the over current device, which is the breaker or fuse.
Don't worry about it some fixtures have no ground terminals. just shove the groung wire to the back of the box. Correction, if the fixture is metal and it shorts out, the metal surrounding the fixture could become electrified. That's why fixtures today are normally grounded to their mounting plates and then the lead is attached to the incoming romex. In the past, attaching these plates to metal boxes (either grounded by an incoming wire or grounded to the BX cable) eliminated the need for a ground wire. If the hot wire hit or shorted to the fixture, it would blow a fuse or circuit breaker. Many electrocutions and fires later, the folks at Underwriters realized that even that method of grounding wasn't sufficent (the old aluminum boxes and bx cables were crappy conductors. Solution; (and I practice what I preach because I remodel many old homes) get a little creative and spend the extra time to wrap a little ground wire to a mounting screw, or piece of metal, on the mounting plate of the fixture and then attach it to your incoming romex ground. On an old fixture, it could mean the difference between a fire and a tripped circuit breaker. If you have any metal boxes, old or new, ground to those too. <><><> Connect a pigtail to the metal canopy, and use a wire nut to connect the safety ground to it.
Just tuck it away in the box. Unless you run ground wires throughout the house it won't serve any purpose.
Porcelain is ceramic so it's a nonmetal.