This is not simply a picture of a flower with pretty colors and sweet fragrance. This is the sexual reproductive organ of a living organism!
Teaching high school I often try to find ways to engage students and find ways to make things sound more interesting than they might have thought. Plant reproduction is one example where I spice it up a little. I start my lesson with PLANT SEX!! This, of course, gets everyone’s attention and interest immediately.
Flowers are amazing structures that advertise sexual reproduction at its most refined and intricate level. The flower must advertise to a pollinator to complete the task and does so usually with the reward of a small amount of nectar or excess pollen. Too much nectar and the pollinator would only visit that one flower, too little and it might not be worth the pollinator’s effort. This symbiosis between plant and pollinator has lead to some extreme adaptations for both parties.
Orchids are at the forefront of flower technology. These intricate structures are designed to ensure the pollinator does its job efficiently and accurately. The small yellow sphere on the top picture is a prepackaged bundle of pollen covered in a sticky glue. The pink bulb shape petal is functionally a landing pad. When the insect lands it must crawl up into the flower to retrieve its nectar prize. In doing so it rubs it back on those sticky pollen packages, which readily attach to the unsuspecting insect. The trade has been made. The next flower that is visited by that insect will be fertilized with that pollen. Not to bad for a plant!
The pollen is accepted at the female part of the flower, the stigma. That is the longer pink structure in the picture above. The pollen, the male reproductive particle, is found on the stamen which is the bright yellow structures deeper in the flower. These different structures often mature at different times to avoid self pollination. Those of you with allergies to pollen, what are you really allergic to? Effectively it’s plant sperm! (the high schoolers love this) Just think about that next time you shove your nose into a flower!
The stigma is specifically designed to accept only a specific shape and size of pollen. In this picture you can see the tiny end of the stigma is ready to receive any wayward pollen grains. This selectivity is why we don’t end up with lots of weird hybrid plants running around. The microscopic structure of pollen is incredible. A quick internet search will show you some great examples. My favorite is the pollen from pine trees. It looks like it has little wings to ride the air currents for miles! Natural selection at its finest!!
Tomorrow: More Plant Sex!