Tomato: Get into the Subway from any station (I'd recommend the one in the main Grass World/Grassland, it's the nearest to the Nexus), and get off at the fifth station (the one with the "!" sign). You'll arrive at the Grayscale Mall. Go up, then right. You should see a door emitting a faint orange light. Enter it to get to the Edible World. Go up until you see an horizontal "road". There should be a tomato rolling to the right. If not, wait or go left to find it more easily. Interact with the rolling tomato.
Wood: Space World, go left and a bit down until you find a blue teleporter among some gray asteroids. Use it. At the moon, walk left or right until you see another blue teleporter, and use it. You'll enter the Testing Area. Now now, this area has twenty tests. Only ten are available at the beginning (you find the Mercury effect in test number six, by the way), if you complete them a new teleporter will be there in the area's entrance, leading you directly to Test 11. Halfway through Test 14 you'll reach a dead end and a blue teleport. It leads you an island at the Grassland. Interact with the green fairy to get the Wood effect.
If you want to get the Wood effect you'll need the Scooter, the Fox, the Candle holder, the Megaphone, the Mercury and the TV.