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Podophyllum peltatun (Mayapple) Berberidaceae
The mayapple is an herbaceous perennial plant native to deciduous forests of eastern North America. It is a very unique plant that has two leaves when it produces a flower under the leaves, and has only one leaf when it does not produce flower.
The mayapple is a spring ephemeral emerging before the canopy of the forest closes and withering later in the summer.
The mayapple grows from below the ground to 30–40 cm tall. They reproduce asexually underground so there are usually many plants growing together that are actually one individual.
Leaf: The leaves are palmately lobed up to 20–30 cm diameter with 5–9 deeply cut lobes. The reproductive plants have 2 or occasionally 3 leaves, and sterile plants only have one leaf. When there is only one leaf, the leaf looks round, and when there are two, the two leaves look like two halves of a round leaf.
Flower: There is one flower maximun on one plant. The flower is white and 3–5 cm diameter with 6–9 petals (most often 6). The stamens are yellow, and there are twice as many stamens as there are petals. The pistil is very thick in the center of the flower with 15–100 ovules. The flower is protandrous, meaning the anthers mature earlier than the stigma. The anthers often dehisce before the flower has opened, and the stigma remains receptive even when the stamens and petals begin to fall from the flower. The flower grows from in between two leaves under the leaves, so it is often not easily seen.
Fruits: The fruits are formed from sexual reproduction for distance dispersal. The fruits are yellow-greenish and 2–5 cm long. It is the flower that shows up in May, not the “apple.” The “apple,” which does not look too much like an actual apple, appears later in summer.
Rhizome: The mayapple reproduces sexually and asexually. It grows rhizomes underground, and new plants grow from the thick rhizomes. Asexual reproduction allows dense local population of clones and costs less.
Life span: The mayapple is a perennial plant.
Toxicity and edibility
The whole plant of mayapple contains toxic substance podophyllotoxin, otherwise known as podofilox, a toxin extracted from the roots and rhizomes of Podophyllum species. The roots and the rhizomes contain 0.3% to 1% by mass of podophyllotoxin. This toxin can be used as a medicine to externally treat genital warts caused by human papillomavirus (HPV). Although the fruits are edible when ripened and soft in moderate amount, immature green fruits are toxic and when consumed in large amounts. The ripened fruits are definitely poisonous as well as being a laxative. Do not consume when pregnant.
The fruits are very sweet and have fragrance like tropical fruits and can be eaten raw like other fruits. When cooking the mayapple, remove the poisonous seeds. It is very hard to separate the seed and pulp, so if seeds are not taken, do not chew on the seeds so the seeds do not break.
Click here for recipes for making Mayapple jelly, Mayapple jam and Mayapple punch.
Mystery about pollination
The Mayapple does not have native pollinators, and it does not self-pollinate
The mayapple is an unusual plant. It has a flower under its leaves so it does not get pollinated by wind; it has no native pollinators because it does not reward pollinators by providing nectar. It is a highly clonal plant, meaning in one population most plants are actually one genetic individual connected by rhizomes, while it is self-incompatible, meaning it does not fruit if the stigma receives pollen from itself. What is going on here?
Self-incompatibility and environmental factors
Since more ovules are always produced than can mature in plants due to limited resources and need for selection, after the ovule is pollinated the flower starts to selectively abort some ovules. The abundance of resource here is the key, so with poor resource the flowers are highly self-incompatible, and with rich resource the flowers shows some self-compatibility.
Non-rewarding and self-incompatible at the same time
Most non-rewarding flowering plants do not have to worry about pollination, because they normally are self-compatible, meaning that their own pollen can pollinate their own ovules. The mayapple, interestingly, has very low self-compatibility while being an extensive clonal plant, which means that one patch of plants is usually one genetic individual, and they cannot provide pollen to each other. The self pollens that fall on the stigma can grow and reach the ovary, showing that the selection for non-self pollen is genetic, and this mechanism is not well-known now.
Observed pollinators of mayapple
The two common observed pollinators are honeybees and bumblebees. Although some pollinators are observed, the visit rate is as low as 0.03-0.06 visit/flower/hour. The mayapple does not provide nectar, but it has copious pollen, which could be what some pollinators seek, like honeybees, which collect pollen and nectar as their food. Honeybees are not native to North America where the Mayapple grows, but they do help the pollination of the species. Some native bumblebee queens are also observed to visit mayapple flowers. The bumblebee queens are nectar-seeking, and the mayapple does not provide nectar, so they are said to be “decieved” to visit the flower.
Plants like the mayapple that does not provide nectar to pollinators are said to get pollinated by deceiving the pollinators, and this is also called deceptive pollination. Deceptive pollination is not uncommon in plants. Some plants get pollinators by mimicking another plant that provides nectar; some plants grow close to other plants that provide nectar so they can also get some pollinator visits; some plants make their flowers look like bodies of certain insects, so the pollinators come to try to copulate but they only get pollen grains on their bodies.
Down-facing flowers: What pollinators does it want to attract?
Most flowers face up to attract high-flying insect pollinators like bees. The flowers of the mayapple hide themselves under the big palm-like leaves and face down. What kind of pollinators does it want to attract?
Facilitated pollination by nearby plants?
One theory about the mayapple is that their pollination is facilitated by nearby plants. In several studies testing this hypothesis, the result turned out to be that nearby plants of different species do not facilitate nor hinder mayapple’s pollination. Growing near other plants do not always facilitate pollination; it can also cause competition for pollinators and increase heterospecific pollen transfer which does not help fruiting.
So, how does the mayapple get pollinated?
The pollination of the mayapple still sounds more like a mystery to me after reading primary resources for many hours. My research so far has made me more confused but more curious too. The orchid family is known for its diverse mechanism of pollination, especially different kinds of deceptive pollination. Looking into other deceptive pollination mechanism might help the understanding of the pollination of the mayapple, and further research is needed to give a clear answer to the question.
Sexual or asexual reproduction?
Some plants have a flower and two leaves, and others only have a big leaf without flower and reproduce asexually by rhizomes. How do they decide?
Page drafted by Wendy Deng