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The most foul-smelling flower in the world is going extinct

  It is the largest flower in the world, and perhaps the smelliest flower. In the past 200 years, large flowers and plants have always been the focus of the world; but in the future, it may go extinct in our eyes.
  In 1818, the British botanist Joseph Arnold was on an expedition with the newly appointed Lieutenant Stamford Raffles in the British Bengulian area (now Bengkulu Province) on the island of Sumatra. A strange giant flower was found. “To be honest, if there are no bystanders around, I might not be able to believe what I saw. The size of this flower is far larger than any flower I have seen or heard of before…” Arnold wrote to a friend Wrote, “It is 1 yard (about 92 cm) wide; its red petals are 12 inches (about 30 cm) long from root to tip.”
  The instinct of the botanist made Arnold cut the flower quickly , And make it into a specimen. Unfortunately, not long after this, Arnold died of fever. The specimen and its corresponding illustrated book were then sent back to the UK for research by Scottish botanist Robert Brown. To commemorate Raffles and Arnold, Brown named this plant Rafflesia arnoldii (Rafflesia arnoldii).
  In the following years, people have discovered other species of large flowers and plants, which are very similar in appearance, smell, and growth cycle. Today, this magical plant combines honor and notoriety. In Indonesia, large flowers and plants are regarded as one of the three national flowers; for ordinary people, their more widely known titles may be “the biggest flower” and “the smelliest flower”; in the eyes of geneticists, they are not. The mystery contained in the genome of the uncompromising “thief in the flower” has not yet been fully solved to this day.
  Rare flower
  In 1993, Arnold large flowers and plants, Phalaenopsis amabilis (Phalaenopsis amabilis), and Jasmine (Jasminum sambac) were jointly selected as the three national flowers of Indonesia. The latter two were awarded this honor for their beautiful appearance, but Arnold’s Big Flower was selected because of its rarity. The Bengkulu province of Sumatra is the main growing area of ​​Arnold’s large flowers and plants. In addition, a few Arnold’s large flowers and plants are also distributed on Kalimantan Island.
  In addition to the limited distribution range, the fleeting flowering of large flowers and plants also makes this kind of flower even rarer. In the life cycle of large flowers and plants that last for several years, the flowering period of 5 to 7 days can only be regarded as a glimpse of it in the long years. Before flowering, large flowers and plants have been “latent” in the host plant for 2 to 3 years. After the orderly completion of sowing and fertilization, the big flowers and plants appeared in people’s field of vision. Then, after another 1 to 2 years of bud and tepal period, about 1% to 18% of large flowers and plants can survive and bloom. As if waking up, the large flowers and plants will bloom suddenly within 1 to 2 days, and then the flowers will wither quickly within 1 week. Within a month, the flowers disappeared without a trace, leaving only the styles of female large flowers and plants, waiting for the birth of new life in solitude. After 6 to 8 months, the fruits of the big flowers and plants mature, and the life picture of silently waiting and suddenly blooming will be staged again.
  Arnold large flowering plants at different stages of the process
  strange flower
  perhaps because silence for too long, large flowers and raring, one stroke out of the world’s largest flower. At present, the largest flower on record comes from Arnold’s large flower grass, which can reach 106.7 cm in diameter and weigh about 11 kg. The center of the flower can even hold a baby. “It is difficult for me to describe the first time I saw the big flowers and plants, because compared to the flowers we are familiar with, the flowers of the big flowers and plants are really too big.” said Charles Davis, a professor of biology at Harvard University. Davis first saw large flowers and plants when he was studying the biodiversity of the area in northern Kalimantan. Now he has been studying large flowers and plants for nearly 15 years. He added: “The color of the large flowers and plants is also very strange, probably between red and brown, and the petals are covered with small white spots. This is completely inconsistent with most people’s imagination of flowers.”
  What is even more strange is that large flowers and plants do not have common plant organs such as roots, stems and leaves. This is not because large flowers and plants use all the nutrients for the development of flowers, but it is closely related to its way of life. Large flowers and grasses are a type of typical parasitic organisms, and their nutrients come from the host plant, so no additional organs are needed to synthesize and transport nutrients. In terms of host selection, large flowers and plants are quite picky, and most of the large flowers and plants in the family Botrytis cinerea take the Vitisaceae creeper as the only host. “If you have ever been trapped in the woods, you will know that one of the best sources of water is the vines of plants… This may be one of the reasons why big flowers and plants choose the creeper genus as their host.” Davis said. In fact, water is the main component of large flowers and plants. It is precisely because a large amount of water is transported to large flowers and plants that they can grow rapidly in the final stage of flower development.
  But what makes the big flowers and plants famous all over the world is not only their monster-like size and peculiar appearance, but also the weird smell similar to carrion they emit-the alias of “Carrion Flower” also comes from this. Davis used a vacuum pump to capture gas molecules emitted from large flowers and sent them to Cornell University for testing. The results of mass spectrometry analysis showed that the chemical characteristics of these gas molecules matched very closely with the gas molecules emitted by rotten flesh.
  This smell is most obvious at noon on the 3rd and 4th day of the flowering period of large flowers and plants, which is also the best period for large flowers and plants to pollinate. For humans, this smell can be described as stinking, but the carnivorous fly insects are eager for it-they are carefully selected pollinators of large flowers and plants, and the maximum distance of a single flight can reach 19-22 kilometers. In order to attract these small flies, the big flowers and plants take great pains: they will increase their own metabolism, so as to emit heat to accelerate the spread of odor molecules; the appropriate temperature can also help the flies to reduce the calorie consumption when visiting the big flowers and plants. When these flies leave large flowers and plants, they carry a very viscous liquid containing pollen on their backs. These fluids can remain active in vitro for several weeks, until the flies bring them to the female flowers. Field surveys conducted by Davis showed that large flowers rarely bloom, so the probability of successful pollination and fertilization is also low. “But if successful,” Davis said, “It was like in a lottery, because the female flowers produce fruit in pregnant with hundreds of seeds.”
  Rafflesia
  But how do these seeds enter the host’s body? This issue is still unresolved. Some scientists believe that these seeds may be eaten by tree shrews, and then expelled by tree shrews and then stick to the feet of elephants to spread. Some scientists believe that ants play an important role in this. Ants may have bitten off the vines of creeper plants or were attracted by the gaps in the vines that ooze sugar water, so that their own large flowers and grass seeds can infect their hosts from the “wounds” of these plants to achieve parasitism.
  Gene thieves
  from form to smell and then way of life, a large number of flowers and the body hidden mysteries. But for scientists, what attracts them the most is the secrets hidden in their genomes.
  In 2014, Jeanmaire Molina, a biologist at Long Island University Brooklyn, decided to study the genes of large flowers. What she wants to know is whether the peculiarities of the big flowers and plants are also reflected on the genetic level. After sequencing the genome of the large flower grass, Molina was surprised to find that they could not detect the presence of the chloroplast genome or other chromosomal genomes. For botanists, this is an incredible discovery, because chromosome-mediated photosynthesis is one of the hallmarks of plants. Protists obtained photosynthesis by swallowing cyanobacteria about 1.5 billion years ago. ability. “Even the plasmodium contains a chromosomal genome, and they have been separated from their photosynthetic ancestors hundreds of millions of years ago.” Molina said. In fact, Dahuacao was the first plant whose chromosomal genome was not detected.

  But this discovery is only the beginning. This year, Davis and his team discovered that the parasitic flowers (Sapria himalayana) not only do not contain chromosomal genomes, but they also lost nearly half of the conserved genes that are widespread in plants. “We know that they must have gene loss,” Davis said, “but we did not expect the loss rate to be as high as 44%.” This study pointed out that the loss rate of catabolic-related genes in parasitic flowers was the highest, reaching 81%. %, and many genes in intron regions that do not code for proteins have also been deleted. You might think that this is to make the genome as small as possible to reduce unnecessary metabolic burden. But in fact, the genome size of parasitic flowers is about 3.2 to 3.5 billion bases, which is almost the same size as the human genome. So, where do these extra genes come from?
  Parasitic flower
  when Davis and his team analyzed the genomes of parasitic flower, they found clues issues: the genome of the parasitic flower full of many genes of other organisms. They estimate that about 1.2% of the genes in its genome come from other organisms. This ratio may seem trivial, but for plants, even 1% is quite surprising. Because the transfer of genes between different species is not mediated by sexual mating, but by a phenomenon called horizontal gene transfer. The frequency of horizontal transfer of bacteria and other prokaryotes is relatively high, which can reach 10% to 20%. But in eukaryotes, horizontal transfer occurs less frequently. Even in the genomes of relatively simple single-celled eukaryotes, genes from other organisms account for less than 1%.
  However, 1.2% of foreign genes still cannot explain why the large flowers and plants have such a huge genome. In this study, Tim Sackton, director of the bioinformatics department of the FAS Informatics Group, helped Davis and his team analyze the sequencing results. He said: “90% of parasitic flower genes are made up of a large number of repetitive fragments.” And, about 60% of the repetitive fragments are freely movable DNA fragments, this element is called a transposon . No one knows why there are so many transposons in the parasitic flower genome.
  For a long time, transposons have been regarded as a kind of “selfish” elements, which are not beneficial to the host, and “to keep these elements silent, organisms need to consume a lot of energy”, Donald Danforth Plant Science Center’s Botany Saima Shahid (Saima Shahid) said. She believes that these elements may help parasitic flowers to acquire some necessary genes: “They may be able to carry some gene fragments and insert these fragments into the genome of parasitic flowers.” Sackton believes that the large number of these elements is due to the existence of these elements. The parasitic flower cannot prevent it from moving around and copying, because some elements come from the host plant, and the parasitic flower may not be able to recognize and silence these elements. “They are like invasive creatures.” Sackton said.
  To solve this puzzle, a more detailed analysis of the genome is required, such as analyzing the connection between transposable elements and other characteristic elements of the genome. But it is precisely because of the existence of these repetitive fragments that it is not easy to analyze the genome of large flowers and plants. In fact, Davis and his team have been trying to unravel the gene mystery of large flowers for the past 15 years, but the highly repetitive gene fragments of large flowers have made genome assembly very difficult. “It’s like completing a jigsaw puzzle. The picture shows a blue sky, and each piece of the puzzle has the same shape and color.” Sackton said metaphorically. It wasn’t until the last 10 years that the emergence of next-generation sequencing technology made it possible to sequence longer DNA fragments, thus getting out of the nightmare of repeated fragments. But even so, according to estimates by Davis and his team, they only resolved 40% of the parasitic flower genome, and the remaining 60% of the genome fragments are still hidden in the fog of repetitive sequences.
  The crisis of big flowers
  In any case, there may not be much time left for Davis and other scientists. The long growth cycle, short flowering period, human activities, and the collection of local residents and scientists have all made large flowers and plants on the brink of extinction. For example, Rafflesia magnifica (Rafflesia magnifica) has been included in the IUCN Red List of Endangered Species since 2008, and the number of this species is still declining. As the first officially named big flower and grass, the survival situation of Arnold big flower and grass is also not optimistic. Agus Susatya, a conservation biologist from Benkulu University in Indonesia, visited three large Arnold flowers and plants in Bengkulu province in 2003. But by 2014, there were no traces of Arnold’s flowers in these three growing areas.
  Molina is now collaborating with the American Botanic Garden to achieve artificial cultivation of large flowers and plants. She hopes that one day the large flowers and plants blooming in the botanical garden may surprise the world with their unique charm. When people stop to admire its beauty, they may also think of the scientific mystery it carries and the survival crisis it faces.

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