looking good! I like the concept...the alchemist needs his/her ingredients = )
Couple of things that if changed, i think would benefit the game:
have the items needed to collect count upwards rather than downwards (3/3 to me means ive got them all)
the plants shoot seemingly random, should be a pattern to help the player time their movements
the jumping doesnt feel like there is gravity but instead a linear movement up to a fixed point and then back down (feels very strange)
add sound and music (they make a huge difference and you dont have to go all out. try audacity and use sound effects from your mouth/or things around you ie: breaking celery makes a good bone breaking noise)
when you die...restart that mission instead of the whole game...i wouldnt of minded playing the whole thing but because of the seemingly random shooting from the plants it got me