The fall semester has begun and I am looking forward to my Plants and People class at Queensborough Community College. This is a course for non-science majors and teaches about all the ways we use plants and why plants are so important in our lives. We cover many topics and the labs are a lot of fun.
One of the main themes throughout the semester is that plants make chemicals we call secondary metabolites. Plants cannot run away from danger, so they protect themselves using chemicals. In some of the images below you can see oil glands. These glands are filled with these metabolites. Imagine a small insect feeding on these leaves and getting a mouthful of some distasteful or poisonous chemical!
The plant makes these chemicals for its own protection, but we take advantage of them for various purposes such as making medicines, perfumes and flavoring our food.
The main difference between herbs and spices is that herbs come from the leaves of plants and spices come from other parts of the plant (seeds, fruit, flowers, roots). Here are a few samples we put under the microscopes.
Oil glands in a mint leaf (Mentha sp.)
Saffron is the stigma (female organ) of the saffron crocus (Crocus sativa)
Oil glands and trichomes (hairs) on the underside of a rosemary leaf (Rosmarinus sp.)
Cloves are the dried unopened flower bud of Syzygium aromaticum
Anise seed with the stigma (female organ) still persisting (Pimpinella anisum)
Oil glands on the leaf of Thyme (Thymus vulgaris)