The calla lily with a comet-like long tail turns out to be poisonous!

Produced by: Science Popularization China

Author: Qin Yalong (Institute of Botany, Chinese Academy of Sciences, Jiangsu Province, Nanjing Zhongshan Botanical Garden)

Producer: China Science Expo

Editor's note: In order to decode the latest mysteries of life science, the China Science Popularization Frontier Science Project has launched a series of articles called "New Knowledge of Life" to interpret life phenomena and reveal biological mysteries from a unique perspective. Let us delve into the world of life and explore infinite possibilities.

In the wild or parks in southern my country, one often encounters the perennial foliage plant Alocasia odora (Roxb.) K. Koch of the Araceae family. It is evergreen, has an elegant shape, and is of great ornamental value.

As an understory herb, the leaves of calla lily have undergone long-term evolution to capture the light spots shining through the forest canopy. Their leaves have become larger and larger, and now can reach more than one meter in length and width.

Calla Lily

(Photo credit: Photo taken by the author)

In the early morning or evening, in a specific environment of high humidity, in order to expel excess water from the body, the edge of the calla lily leaves will "spit out" liquid water droplets, which will condense at the tip of the leaf and then drip. In addition, the inflorescence of the calla lily resembles Guanyin, so it has the nickname "Dripping Guanyin". In the plant world, if you observe carefully, the phenomenon of spitting water is still very common. Even some fungi (mushrooms) sometimes "spit water", which is called the fungal "drip phenomenon".

The phenomenon of "water spitting" of Phyllostachys olgensis

(Photo credit: Photo taken by the author)

Alocasia is poisonous

Calla lilies contain toxic ingredients such as calcium oxalate needle crystals, saponin glycosides, and calla lilies. If you are not careful, the juice of calla lilies will cause itching when it touches the skin, and it may cause blindness if it drips into the eyes. Ingestion of calla lily rhizomes may even lead to death due to suffocation or cardiac arrest. There are occasional reports of calla lily poisoning in life, so when you see a calla lily, you can watch it from a distance and not touch it.

In the wild, some calla lilies have regular circular holes on their leaves, which are the masterpieces left by leaf beetles eating the calla lily leaves. When the calla lily is eaten or damaged, the toxin is released through the leaf vein system.

Although calla lilies are poisonous, when leaf beetles eat calla lily leaves, they will quickly nibble a circle of leaflets on the large leaf before the toxins are transmitted, cutting off the transmission of toxins through the leaf veins, and then enjoy the leaves with peace of mind. The amazing thing is that the regular circle is the largest leaf area that leaf beetles can obtain by nibbling the same length, so every bite is not in vain.

Holes on the leaves of calla lily

(Photo credit: Photo taken by the author)

Inflorescence structure and flowering phenology of Alocasia lily

As a plant of the Araceae family, the monoecious spadix of Alocasia is protected in a spathe. The spathe is divided into two parts: the lower part is closed, ovate or short elliptical, and the upper part is boat-shaped and oblong.

Calla lilies bloom all year round and have their own fragrance. The inflorescence is dysgenic , and from top to bottom, they are appendages, fertile male flowers, sterile male flowers, and female flowers . The appendages are located at the top of the inflorescence and are cone-shaped.

Alocasia inflorescence structure and flowering phenology, a: inflorescence structure;

b‒e: Inflorescence development process (b: bud stage; c: female flower stage; d: male flower stage; e: fruiting stage)

(Image source: References)

When the calla lily blooms, the male flowers are responsible for producing pollen, the sterile male flowers provide food for pollinating insects, and the female flowers receive pollen and produce fruits.

The inflorescence of calla lily also has the characteristic of dioecious sex . The female flowers in the inflorescence mature first, and the male flowers mature later . There is a constriction between the upper and lower bracts of the spathe outside the inflorescence, which separates the fertile male flowers in the upper part of the inflorescence from the female flowers in the lower part.

The inflorescence of calla lilies has a flowering thermogenic effect. During the flowering period, the inflorescence attracts pollinating insects and provides them with shelter by raising the temperature. At the same time, the temperature rise of the inflorescence can also enhance the fragrance of the flowers and promote the development of flower organs, which is relatively consistent with the flowering thermogenic phenomenon of magnolia and lotus.

During the female flowering period, the fragrance of the calla lily inflorescence is the strongest, the stigma is the most sticky and contains a small amount of secretions. At this time, the flowering heat effect of the appendages and male flower area is significant, and the contraction of the spathe has not yet completely tightened. All flower visitors can enter the female flower area through the contraction, including pollinators carrying foreign pollen to help pollinate the female flowers.

During the male flowering period, the fragrance and heat generation of the inflorescence gradually weaken. At this time, the spathe has completely contracted, and mature pollen and all flower visitors can no longer reach the female flower area, so whether the inflorescence will bear fruit is a foregone conclusion.

Calla lily berries

(Photo credit: Photo taken by the author)

When pollination of the female flowers of the calla lily is complete, the red berries inside will appear as the infructescence matures. Birds are attracted by the bright colors of the berries to eat them, and then excrete the calla lily seeds in their feces, helping the calla lily to spread its seeds over long distances.

Flower Visitors and Pollinators

During the pollination period, plants use floral signals such as color, smell and shape to attract insects, birds and other species to visit. Depending on the functions of the visiting insects, they can be divided into flower visitors and pollinators.

Flower visitors mostly come to eat pollen, nectar, secretions or floral tissues, or stay at the inflorescence ovipositor or occasionally. Among them, flower visitors who truly help plants complete pollination as effective carriers of pollen transfer can be called pollinators.

Generalized pollination system

For those pollinators and plants whose pollination relationship is not exclusive, it belongs to the generalized pollination system. For some generalized pollinated plants, most flowers will produce a large amount of pollen, which can not only meet the pollination and feeding needs of pollinators, but also meet the pollen loss caused by a large number of flower visitors, resulting in low pollination efficiency. Most flowering plants in nature belong to the generalized pollination system.

Specialized pollination system

The latest research by Ding Xiang and others points out that the calla lily fruit fly C. alocasia and the calla lily fruit fly C. xenalocasiae of the genus Colocasiomyia are highly specialized pollinating insects in the pollination process of calla lilies, and they have established a specialized pollination system with calla lilies.

During the female flowering period, taro fruit flies carry foreign pollen through the contraction of the spathe into the female flower area for pollination. During this process, they feed on the secretions of the stigma of the male sterile area and the female flower area. During the male flowering period, taro fruit flies move in the fertile area of ​​the male flower, feeding on pollen and mating, and then carry pollen from the fertile male flower area to another calla lily inflorescence for pollination.

In this pollination system, although 10 species of non-pollinating insects such as the family Apidae, family Pederidae and family Tarsonematidae often visit the inflorescences, they do not participate in pollination. Instead, they compete with pollinators for pollen and inflorescence secretions, and even reproduce, thus competing with the pollination and reproduction of the taro fruit fly.

Common activities of insects and their offspring visiting calla lilies: a‒c: Activities of offspring of taro fruit flies in the inflorescence at different periods;

a: Taro fruit fly eggs (female flower stage); b: Taro fruit fly larvae (male flower stage);

c: taro fruit fly pupa (fruiting stage); d: flower visitors transfer pollen to stigma (female flower stage);

e: Apidae flower visitors collect pollen (male flowering period); f: Apidae flower visitors nibble on sterile flowers (female flowering period);

g: traces of gnawing on sterile flowers; h: hatched larvae of the family Pseudocercidae (sterile area of ​​male flowers).

(Image source: References)

Amazingly, the reproduction process of taro fruit flies in the inflorescence of calla lilies matches the growth stage of the inflorescence of calla lilies. The taro fruit flies lay eggs during the female flowering period, develop into larvae during the male flowering period, and grow into pupae during the fruiting period.

In nature, many plants have established specialized pollination systems with specialized pollinators.

Banyan tree-fig wasp specialized pollination system

There are more than 800 species of banyan trees in nature. They have undergone about 75 million years of co-evolution with fig wasps, gradually forming a highly specialized mutualistic symbiotic system, which has become the most specialized pollination and symbiotic system known to date.

Due to the unique "hidden inflorescence" structure of the banyan tree, only fig wasps can help it with pollination in nature.

Symbiotic relationship between fig and fig wasp

(Photo source: World Knowledge Pictorial)

Fig wasps are divided into pollinating fig wasps and non-pollinating fig wasps. Usually, each fig tree has only one specific pollinating fig wasp for pollination. Although some figs may coexist with several to dozens of non-pollinating fig wasps, they almost never pollinate female flowers.

Similar to calla lilies, for monoecious banyan trees, the female and male flowers in the same inflorescence mature at different times. The figs in the female flowering period will release special volatiles to attract specific pollinating fig wasps that carry male flower pollen and drill into the new inflorescence in the female flowering period to complete pollination.

Yucca serrata - Specialized pollination system of the yucca moth

The yucca plant is native to North America and blooms in August and September. The large panicles are closed during the day and open at night. The flowers of the yucca plant have no sepals, but have six tepals and six stamens, surrounded by a compound pistil formed by the union of three carpels. The lower half of the pistil is columnar, with the top split into three and turned outward.

Yucca

(Photo credit: Photo taken by the author)

In China, the Phoenix Yucca blooms every year but never bears fruit. This is because the only pollinating insect in its native North America is missing: the yucca moth. In China, the Phoenix Yucca blooms at night, emitting a unique fragrance that attracts yucca moths. At this time, the visiting yucca moths have already completed mating, and the female moth will first fly to the top of the stamens, collect pollen and roll it into a ball.

Afterwards, the female moth flies to another flower with the pollen mass and stops on the side of the pistil column. They will pierce the ovary wall with their ovipositor and lay 1-6 eggs. After laying eggs, the female moth will climb to the top of the stigma and insert the pollen mass collected from the previous flower as deep as possible through the hole at the top of the pistil to help the yucca complete pollination.

Yucca flowers

(Photo credit: Photo taken by the author)

After pollination, the ovary of the yucca gradually develops and expands. After the baby yucca moth hatches in the ovary, it feeds on some of the fresh seeds of the yucca, eventually breaking through the wall and burrowing into the soil to pupate. When the yucca blooms the following year, the yucca moth in the pupa breaks out of the cocoon, finds a partner to mate, flies to the yucca flower inflorescence to pollinate and lay eggs, and begins another cycle of life.

In this way, the yucca and the yucca moth underwent a long period of co-evolution, with the yucca moth becoming the only pollinator of the yucca. The yucca provided shelter and food for the moth's reproduction, and the two built a specialized pollination system and achieved an obligate symbiotic relationship.

Specialized pollination system of Aquilegia columbine

In life, there is another type of plants with very high appearance value, which have also established a specialized pollination system with pollinators. They are the Aquilegia plants of the Ranunculaceae family.

The name of Aquilegia serrata comes from the ancient Chinese farming and sowing tool - the plow, because the lower part of its petals often extends into tubular spurs, which look very much like the plow legs of a plow.

The nectar tissue inside the spur of Aquilegia secretes nectar that pollinators like, but this nectar is not prepared for all flower visitors. Only those flower visitors who help Aquilegia pollinate can obtain the delicious nectar after a long period of co-evolution.

Aquilegia

(Photo credit: Photo taken by the author)

The length and shape of the inflorescence of different species of Aquilegia vary. Through the inflorescence and the nectar at the bottom of the inflorescence, each type of Aquilegia has specific pollinators such as hawk moths, drones, hummingbirds, etc. to help it complete pollination, thus establishing a specialized pollination system.

Comet orchid - Specialized pollination system of long-beaked hawkmoth

In 1862, British naturalist Darwin received an orchid specimen from Madagascar, Africa. The flower of the specimen had a spur as long as 30 centimeters. He guessed that there must be a hawk moth with a mouthpart (beak) of comparable length that could suck the nectar at the end of the spur and pollinate it, so people called it Darwin's orchid. Because its flower shape looks like a comet with a long tail, it is named "Big Comet Orchid". Because of its extra-long spur, its scientific name is Angraecum sesquipedale Thouars.

Long-range comet blue

(Photo credit: Photo taken by the author)

It was not until 1903 that the long-beaked hawk moth predicted by Darwin was discovered in Madagascar, with a beak as long as 30 centimeters. In 1992, people first filmed the long-beaked hawk moth pollinating the long-spur comet orchid, perfectly illustrating the co-evolution of plants and pollinators, which built a specialized pollination system and reproduced together in Madagascar.

Conclusion

After a long period of evolution, about 90% of the world's angiosperms need insects, birds and mammals as media to spread pollen. They constitute unique generalized pollination systems and specialized pollination systems, which jointly promote the evolution and reproduction of animals and plants, and continue to tell the survival wisdom of all things in nature.

References:

1. Ding Xiang, Yu Yuanjun, Song Xiqiang, et al. Specialized pollination system of Alocasia with generalized flower visitors[J]. Biodiversity Science, 2024, 32 (6): 24069, pages 1-11.

Note: Latin text should be italicized