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標題: [植物保育] 美植物學家發現 全球「第一朵花」
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發表於 2015-8-19 11:04  資料 文集 短消息 
美植物學家發現 全球「第一朵花」

19 August 2015

【明報專訊】美國植物學家周一發表研究指出,他們發現了可能是全球「第一朵花」,這種古植物距今1.25億至1.3億年,生長在西班牙湖水中,沒有花瓣,只有一粒種子。
沒明顯「花的構造」

該植物學名為Montsechia vidalii,是專家們研究了1000多塊化石後確認。其實科學家早就知道有Montsechia vidalii存在,Montsechia vidalii的化石一個多世紀前就在西班牙中部伊比利山脈(Iberian Range)以及庇里牛斯山(Pyrenees)蒙特塞克山脈(Montsec Range)的石灰岩沉澱物中發現。有份撰寫今次研究的專家迪爾切(David Dilcher)表示,以前的科學家沒有正確解讀這些化石,因為Montsechia vidalii「沒有明顯『花的構造』,例如花瓣或是製造花蜜的構造來吸引昆蟲,且終其一生生長在水下」。

專家指出,Montsechia vidalii可能像水草,生長在淡水中,它只有單一種子,這是稱為「被子植物」(angiosperm)的開花植物特徵。它的歷史可溯及1.25億至1.3億年前,大約是禽龍和腕龍等恐龍生活在地球的年代。迪爾切(David Dilcher)說﹕「根據最新的分析,我們現在知道,Montsechiavidalii就算不比『中華古果』更古老,至少也屬同一年代。」此前在中國遼寧發現的有花植物化石「中華古果」,距今約1.45億年。

(法新社/BBC)

http://news.mingpao.com/pns/%E7% ... 00014/1439921176706


圖片: [Montsechia vidalii的化石] Ming Pao.jpg (2015-8-19 11:04, 327.2 K)

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發表於 2015-8-19 11:09  資料 文集 短消息 
Fossilised remains of world’s oldest flower discovered in Spain

Ancient aquatic plant thought to be world’s first flower; studying it could provide a solution to modern pollination issues linked to decline of bee population

A beautiful aquatic plant, dating back to the start of the Cretaceous period, is believed by scientists to be the oldest flowering plant on Earth.

New analysis of the fossilised remains from central Spain and the Pyrenees show that the plant is about 130 million-years-old, meaning it was around at the same time as feathered dinosaurs.

The plant, Montsechia vidalii, resembles the modern-day coontail - commonly used to populate aquariums - and is thought to have grown underwater in shallow lakes.

The plant snatches the title of world’s oldest flower from the hands of another ancient plant, Archaefructus sinensis, discovered in 125 million-year-old fossils from Liaoning Province in China.

“The ‘first flower’ is a bit of a poetic concept, but that aside, we do believe this is the oldest we have discovered so far,” says David Dilcher at Indiana University, who led the analysis.

To study the ancient plant, Dilcher and his team slowly dissolved the limestone around more than 1000 fossils. This left them with small fragments of the plant that could then be bleached and their structure examined using powerful microscopes.

The plant appears to have had no roots or petals. Its leaves were arranged in two forms: either in a spiral or opposite one another along an axis. The plant sprouted several tiny flowers, each of which contained a single seed.

Animals in this time period hadn’t developed any role in the dispersal of seeds, says Dilcher. Instead, the plant is thought to have separate male and female flowers. It seems likely that the seeds were released straight into the water, where they floated off to fertilise another plant.

“This is a fascinating and provocative analysis of the new fossils,” says Sam Brockington, a research fellow in the department of plant sciences at Cambridge University. “It has always been difficult to say whether the first flowering plants emerged in aquatic conditions, but this paper emphasises how important aquatic environments were for the earliest flowering plants.”

Sometime in the middle of the Cretaceous period the diversification of the flowering plant population exploded, developing into the beautiful blooms we know today, as well as influencing the wildlife that evolved alongside. Dilcher says that we wouldn’t be here at all if it weren’t for plants like Montsechia vidalii. “We are a product of the many stages of evolution that went hand-in-hand with the evolution of flowering plants,” he says.

Bernard Gomez of Claude Bernard University, Lyon, and co-author of the paper, which is published today in PNAS, says that there may yet be an even older flowering plant. There’s evidence of pollen dispersed in fossils that are around 140 million years old, he says.

One thing is for sure, says Dilcher, “we need to understand as much as we can about flowering plant evolution because right now we’re facing a world crisis.” Most modern flowering plants need animal pollinators to reproduce, with bees serving that role for many of our most important crops. Yet bees are declining in the US and Europe.

“This plant shows us where it all began,” says Dilcher. “If we know more about their evolution, we might come across alternative pollinators that are hidden out of sight today but played a role in the past that we could encourage again.”

http://www.theguardian.com/scien ... scovered-cretaceous


圖片: [An artist’s reconstruction of Montsechia vidalii. The plant is thought to have male and female flow] Theguardian1.jpg (2015-8-19 11:09, 216.03 K)



圖片: [Montsechia vidalii lived alongside the dinosaurs of the Cretaceous period. The researchers say the p] Theguardian2.jpg (2015-8-19 11:09, 78.76 K)

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發表於 2015-8-19 11:13  資料 文集 短消息 
Paleobotanist identifies what could be the mythical 'first flower'

New analysis represents major change in the presumed nature of the planet's earliest angiosperms
Date: August 17, 2015
Source: Indiana University
Summary: Paleobotanists in Europe have identified a 125 million- to 130 million-year-old freshwater plant as one of earliest flowering plants on Earth.

Indiana University paleobotanist David Dilcher and colleagues in Europe have identified a 125 million- to 130 million-year-old freshwater plant as one of earliest flowering plants on Earth.

The finding, reported Aug. 17 in the Proceedings of the National Academy of Sciences, represents a major change in the presumed form of one of the planet's earliest flowers, known as angiosperms.

"This discovery raises significant questions about the early evolutionary history of flowering plants, as well as the role of these plants in the evolution of other plant and animal life," said Dilcher, an emeritus professor in the IU Bloomington College of Arts and Sciences' Department of Geological Sciences.

The aquatic plant, Montsechia vidalii, once grew abundantly in freshwater lakes in what are now mountainous regions in Spain. Fossils of the plant were first discovered more than 100 years ago in the limestone deposits of the Iberian Range in central Spain and in the Montsec Range of the Pyrenees, near the country's border with France.

Also previously proposed as one of the earliest flowers is Archaefructus sinensis, an aquatic plant found in China.

"A 'first flower' is technically a myth, like the 'first human,'" said Dilcher, an internationally recognized expert on angiosperm anatomy and morphology who has studied the rise and spread of flowering plants for decades. "But based on this new analysis, we know now that Montsechia is contemporaneous, if not more ancient, than Archaefructus."

He also asserted that the fossils used in the study were "poorly understood and even misinterpreted" during previous analyses.

"The reinterpretation of these fossils provides a fascinating new perspective on a major mystery in plant biology," said Donald H. Les, a professor of ecology and evolutionary biology at the University of Connecticut, who is the author of a commentary on the discovery in the journal PNAS. "David's work is truly an important contribution to the continued quest to unravel the evolutionary and ecological events that accompanied the rise of flowering plants to global prominence."

The conclusions are based upon careful analyses of more than 1,000 fossilized remains of Montsechia, whose stems and leaf structures were coaxed from stone by applying hydrochloric acid on a drop-by-drop basis. The plant's cuticles -- the protective film covering the leaves that reveals their shape -- were also carefully bleached using a mixture of nitric acid and potassium chlorate.

Examination of the specimens was conducted under a stereomicroscope, light microscope and scanning electron microscope.

The age of the plant at 125 million to 130 million years is based upon comparisons to other fossils in the same area, notably the freshwater algae charophytes, which places Montsechia in the Barremian age of the early Cretaceous period, making this flowering plant a contemporary of dinosaurs such as the brachiosaurus and iguanodon.

The precise, painstaking analysis of fossilized structures remains crucial to paleobotany, in contrast to other biological fields, due to the current inability to know the molecular characters of ancient plants from millions of years ago, Dilcher said.

This careful examination was particularly important to Montsechia since most modern observers might not even recognize the fossil as a flowering plant.

"Montsechia possesses no obvious 'flower parts,' such as petals or nectar-producing structures for attracting insects, and lives out its entire life cycle under water," he said. "The fruit contains a single seed" -- the defining characteristic of an angiosperm -- "which is borne upside down."

In terms of appearance, Dilcher said, Montsechia resembles its most modern descendent, identified in the study as Ceratophyllum. Also known as coontails or hornworts, Ceratophyllum is a dark green aquatic plant whose coarse, tufty leaves make it a popular decoration in modern aquariums and koi ponds.

Next up, Dilcher and colleagues want to understand more about the species connecting Montsechia and Ceratophyllum, as well as delve deeper into when precisely other species of angiosperms branched off from their ancient forefathers.

"There's still much to be discovered about how a few early species of seed-bearing plants eventually gave rise to the enormous, and beautiful, variety of flowers that now populate nearly every environment on Earth," he said.

Story Source:

The above post is reprinted from materials provided by Indiana University. Note: Materials may be edited for content and length.

Journal Reference: David L. Dilcherd et al. Montsechia, an ancient aquatic angiosperm. PNAS, August 2015 DOI: 10.1073/pnas.1509241112

http://www.sciencedaily.com/releases/2015/08/150817160613.htm

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