Lecture: Reproductive Redundancy: Narrator: Listen to part of a lecture in a botany class. Professor: Another thing about the reproductive adaptations of plants is that these adaptations are often redundant. Some plants use a variety of different mechanisms, not just a single method to pass the genes along to the next generation. Steve: So it's like having a plan B in case plan A fails. Professor: Precisely. Good analogy, Steve. To illustrate reproductive redundancy, let's look at one flowering plant that's pretty famous in scientific circles for its reproductive fitness. And that's the Viola or violet as it's commonly called. For instance, one strategy violets use is cross-pollination by insects and not just bees. Violets rely on a variety of insects to spread their pollen to other violets and fertilize them. To attract pollinators, many violets produce colorful fragrant flowers like these. Now there are about 500 species of violet and many produce blooms from late February through mid-July, longer than many other perennials. So that provides a large window of time for pollination. But there's more to it than that. With some of these species, several times during the life of the flowers, the stalk changes positions. And the petals themselves actually shift very gradually. Why does this happen do you think? Steve: To take advantage of the available sunlight? Professor: No, though some plants do that. Okay. Picture a bee, a wasp, a pollinating fly, and a butterfly all with different maturations and enemies, each foraging for nectar in its own particular way and at a slightly different time of year. Now over the course of a long flowering season, violets that change petal positions from horizontal to vertical for instance, that sort of customized feeding platforms, their blossoms to accommodate whatever's flying around at a particular time. They are going to be the most successful. Okay. But even after the blooming season is over, the strategies continue. Some violet species start producing another kind of flower, fat green buds that never open. These buds are called cryptic flowers. Cryptic flowers form at the bottom near the base of the plant between the leaves, but they never bloom. So cross-pollination by insects isn't possible. Instead, cryptic flowers self-pollinate to produce seeds. So even if cross-pollination gets disrupted by frost or droughts or pest or by a low number of pollinators, violets with cryptic flowers can still reproduce. Now, violets tend to produce lots of seeds. But seeds are even more useful if they get spread out, because ... Female Student: Well, if the seeds just fell in a pile at the base of the plant, they could be eaten all at once if a bird or a mouse found them, right? Professor: Yes. Or if the seeds do germinate, they wind up competing for nutrients with each other and with their parent plant. To avoid this, many violets produce their seeds in a dry fruit called the capsule. As this capsule ripens, its walls dry out and eventually the seeds are expelled under pressure and shoot into the air. This reminds me of the story about one violet species that can supposedly shoot its seeds almost 5 meters away from the parent plant. And that had always seemed pretty out there to me. But one day when I was expecting one of my ivy-leaf violet, I noticed an open seed capsule. I could see the brown seeds all lined up on the margins. I decided to bring the plant upstairs to show a colleague, but as I was walking I heard this pop and ping. The seed capsules from my little ivy-leaf violet had released the seeds, which burst out and actually hit the ceiling almost 2 meters above my head. Now let's look at the design of the seeds themselves. A lot of violet species produce seeds that are tipped with a tiny oil gland. So basically you have these oil tip seeds. And this oil is very attractive food for certain kinds of foraging ants. So what happens is the oils collect these seeds, take them into their underground colony, scrabble the oil with their mandibles, their jaws, and then dump the remains of the seeds in a pile. And this is where they sprout again far away from the parent plant.