Monday, July 08, 2013

Behavior of wheat awn


Recently, an interesting discussion was active in GrainGenes mailgroup, describing about an unusual behavior of wheat awn asking for further explanation on the phenomenon. The story went like this:
During a recent trip Mr Norman Rossen and colleagues met a lady who was a worker at a US Department of Agriculture facility where she did chemical research on wheat components. Mr Rossen happened to relate an experience about wheat to this lady which she never had heard and did not believe. When he was a young boy, while traveling with his dad along rural Pennsylvania they happened to stop along a wheat field. His father broke off an awn of wheat, put it on his bare, but hairy, forearm and told him to watch what happened. The head of wheat very slowly moved up his fathers arm. He recalls that the same movement repeated when they put the head of wheat on his not-quite-so-hairy arm too.

I believed this is a common phenomenon with dry awns of many grass species, especially the ones which make longer awns. I have seen kids playing with some grass species whose awns are long and 'L' shaped which spin around when they wet them. Such grass species are common in tropical South India, which is not a wheat growing region. Nevertheless the phenomenon was very similar to what Mr Norman experienced with the wheat awn.

The reason for the movement is nothing but moisture. The dry awn must be having its cells under tension because of the loss of moisture and when it absorbs water it probably must be expanding causing the movement. For the grass awns, wetting is must for the rotation. So the movement Mr Nornam observed on his dad's and his arms could have been caused by the perspiration which the wheat awns absorbed causing the movement.

Dr Maarten van Ginkel of the Plant Genetics and Genomic Division of the Primary Industries Research Victoria (PIRVic) says he has regularly demonstrated this phenomenon to interested parties using wild oats. Hold the separated seed-filled floret by the tip of the L shaped twisted awn, wet the twisted region at the base of the awn with some spittle and the floret will make a 360-degree turn in the air and sometimes more as the awn unwinds. The assumption is that lying on the ground the L-shaped tip is lodged in between some rocks or soil clods, and when the first rains set in or even excessive dew, the seed drills itself into the soil by the spring-loaded action of the trapped awn unwinding. The tips of wild oat seeds are heavily bristled forming an arrow-shaped projectile of the glumes closely adhering to the seed. Thus a handful of oat seeds (rather seeds plus fused-glumes) on the open soil one day the next morning can have fully drilled themselves into the soil, leaving no trace.

In a recently published article in Science Elbaum et al., (2007) explains the phenomenon of movement of the awns. The dispersal unit of wild wheat bears two pronounced awns that balance the unit as it falls. They discovered that the awns are also able to propel the seeds on and into the ground. The arrangement of cellulose fibrils causes bending of the awns with changes in humidity. Silicified hairs that cover the awns allow propulsion of the unit only in the direction of the seeds. This suggests that the dead tissue is analogous to a motor. Fueled by the daily humidity cycle, the awns induce the motility required for seed dispersal.

Elbaum,R., Zaltzman,L., Burgert,I., Fratzl,P. (2007) The Role of Wheat Awns in the Seed Dispersal Unit. Science 316: 884 - 886

More references:

Peart, M.H. 1979. Experiments on the biological significance of the morphology of seed dispersal units in grasses. J. Ecol. 67: 843-163.
Peart, M.H. 1981. Further experiments on the biological significance of the morphology of seed dispersal units in grasses. J. Ecol. 69:425-436.
Peart, M.H. 1984. The effects of morphology, orientation, and position of grass diaspores on seedling survival. J. Ecol. 69:425-436.

Saturday, January 26, 2013

A tribute to Nikolai Ivanovich Vavilov (1887-1943)


I thought my next post should be a tribute to Nikolai Ivanovich Vavilov. Today (26 Jan 2013) marks the 70th death anniversary of this legend. The great who led us to the depths of origin of cultivated species... A great warrior like Gregor Mendel, who lost to the bureaucracy of science. Did he really lose?

Nikolai Ivanovich Vavilov (1887 - 1943)

A pioneer geneticist and the person who organised the earliest potato-collecting expeditions to the Andes after 1926, when many species and varieties were lodged in the then Horticultural Research Institute of St. Petersburg, where he and others carried out genetic analyses and field trials.

Founder-Director of the Soviet Academy of Agricultural Sciences

From 1920 to 1930, Vavilov organised and participated in several scientific expeditions to collect culturally important and cultivated plants from Afghanistan, Japan, China, Central and South America, Europe, North Africa, the Middle East, Ethiopia, Eritrea and Yemen. After 1938 he collected widely in the then U.S.S.R. By 1940 some 200 thousand plant species had been lodged in Russia, many sown annually in some 150 field research stations, some outside Russia.

A pioneer plant geographer, Vavilov published in 1924 a very important work The Centres of Cultivated Plant Origins - today known to biographers as "The Vavilov Centres", seven in number, and essentially the origins of most important agricultural plants. There are a few smaller centres recognised. Thus it was with great gratitude that in 1991 the writer received both membership of the then U.S.S.R. (Soviet) Academy of Agricultural Sciences and, the foundation gold Vavilov medal, a likeness of Vavilov. My own major is also in Biogeography, but the honours bestowed on me by the Academy are for my publications in Permaculture (1978 - 2000), as pioneer work on the conscious design of sustainable agricultural systems. A brief biography of Vavilov, forwarded to me by Bogdan Popov of Kiev, who was my student and interpreter for courses in Russia and elsewhere (abridged here) follows:

Vavilov was born in Moscow, his family were merchants. An elder brother was the famous physicist Sergei Ivanovich Vavilov. In 1906 Vavilov graduated from the Moscow College of Commerce, then joined the Moscow Agricultural Institute under the scientists K.A. Timiryasev, D.N. Pryanishnikov and V.R. Villiamo. At this Institute Vavilov studied in diverse disciplines, and published on the molluscan predators (snails, slugs) of plants in the Moscow province. He graduated in 1911 and worked on plant breeding, then transferred to the Bureau of Applied Botany (Director R.E. Regel) and the Laboratory of Mycology and Phytopathology (Director A.A. Yachevskiy).

From 1913 to 1914 Vavilov studied at the University of Cambridge in England under Prof. W. Bateson, and at the John Innes Horticultural Institute in London, a centre of composting research. There he published on the development of plant immunity to fungal diseases. In 1914, he went to France to study at the seed company of Vilmorin, and then to Germany ( E.Gekkel). At the outbreak of war he left Germany after great difficulty and returned to Russia, there publishing on plant immunity to viral infections.

In 1916, collecting in Fergana, Northern Iran, and the Pamirs, his material allowed him to discover the laws of homological series, hence to trace the origins of the cultivated varieties of plants. In 1917, Vavilov became Professor of Botany at the University of Saratov, but in 1921, he and colleagues moved to St. Petersberg where they set up the Horticultural Research Institute specifically intended to centre the collection of the species of cultivated plants in the world. Accessions were available for growing trials and genetic studies in the U.S.S.R. and elsewhere, but the collections have never been equalled.
In 1929 Vavilov and others founded the Lenin Academy of Sciences in Agriculture, forerunner of the U.S.S.R. Academy of Agricultural Sciences, and finally (after Glasnost) the Russian Academy of Agricultural Sciences. Vavilov was founder-president.

In the mid 1930s, Lysenko and his supporters developed a group of "Agro-biologists" who promised rapid crop improvement; their theories attracted Stalin and his secret police chief Beria, so that the "neo-Lamarkians" were in fact destroying support for Soviet genetic sciences in the scientific mode. Lysenko was able to instigate the arrest of Vavilov and his friends on 6th August, 1940, when he was collecting in the western Ukraine.

In prison, Vavilov was subjected to severe interrogations - a total duration of 1,700 hours - and was eventually sentenced to death in July 1941, later reduced to twenty years in a death cell, underground and without windows. There he contracted scurvy and developed severe dystrophy, dying on the morning of January 26th, 1943, still in Moscow. His family nearby were not told of his fate.

As a member of the Royal Society of London, he and others published The Origin, Variation, Immunity and Breeding of Cultivated Plants, translated and edited by K.S. Chester (English edition 1951).

All evidence of Vavilov's tenure at the Moscow headquarters of the Academy was removed by his fellow scientists on his arrest, and remained hidden until Stalin had died and Beria was replaced in the 1950s.

Today, Academy members (Nikinov was President in my day) speak openly and with great affection of Vavilov; Lysenko and his works are buried. The K.G.B. (then N.K.V.D.) destroyed Vavilov's manuscript A World History of Agricultural Development in 1941 as being of no value to his case!

So, a true world patriot and pioneer plant explorer was killed, aged 66 years, by jealous and vicious enemies, isolated from friends and family. He is survived by his successors and the seven hundred members of the Academy. Many scientists starved to death among the bags of grain and potatoes at the Academy in St. Petersburg during the 900-day seige by the Nazis. They died, preserving for the future the seeds of survival. We owe them all our thanks.

Vavilov died because he asserted the truth.

The Vavilov Centres

From Symons (1967) Agricultural Geography pp 11 to 12:

Vavilov listed eight independent centres of origin of the world's most important cultivated plants, based on expeditions he and other Russian scientists made throughout the world between 1916 and 1934:

1. China: The earliest and largest independent centre . . . consists of the mountainous regions of central and western China, together with the adjacent lowlands. Vavilov credited this region with important millets, buckwheat, soya beans, legumes and fruits and listed 136 endemic species.

2. India, including Burma and Assam, excluding north west India: 'India is undoubtedly the birthplace of rice, sugar cane, a large number of legumes and many tropical fruit plants, including the mango and numerous citrus plants. . .' Pulses, gourds and vegetables including cucumber, lettuce and radish were among the 117 listed species.

Also, the Indo-Malayan centre, including Indonesia and the Philippines: 55 species were listed by Vavilov.

3. Central Asia, including north west India, Afghanistan, Tadjikistan, Uzbekistan and western Tian-Shan: To this region were attributed a range of wheats, important legumes including peas, lentils and beans, and cotton. 42 species were listed.

4. The Near East, including the interior of Asia Minor, Transcaucasia, Iran and the highlands of Turkmenistan: Nine botanical species of wheat and rye, the grape, pear, cherry, fig, walnut, almond and alfalfa were among the 83 species listed.

5. The Mediterranean: home of the olive and many vegetables, was an important secondary source, in which man's part in selecting the more promising varieties for cultivation is particularly notable. 84 species were listed.

6. Ethiopia: Vavilov's expedition in 1927 established the importance of this area as an independent centre of origin, important especially for varieties of wheat, barley, sorghum and millet. 38 species were listed.

7. South Mexico and Central America (including the Antilles): Here was placed the primary centre of maize (corn), the sweet potato and upland cotton, and 49 endemic species were listed.

8. South America: The Russian expedition of 1932-1933 stressed the importance of the high mountainous area of Peru, Bolivia and part of Ecuador, remarkable for its endemic plants, notably numerous species of potato. Other centres distinguished were the island of Chiloe and the Brazilian-Paraguayan area. A total of 62 species were listed.

Major N.I.Vavilov's Expeditions

Expedition to Iran (Hamadan and Khorasan) and Pamir (Shungan, Rushan and Khorog).

Acquaintance trip to Canada (Ontario) and USA (New York, Pennsylvania, Maryland, Virginia, North and South Carolina, Kentucky, Indiana, Illinois, Iowa, Wisconsin, Minnesota, North and South Dakota, Wyoming, Colorado, Arizona, California, Oregon, Maine).

Expedition to Afghanistan (Herat, Afghan Turkestan, Gaimag, Bamian, Hindu Kush, Badakhshan, Kafiristan, Jalalabad, Kabul, Herat, Kandahar, Baquia, Helmand, Farakh, Sehistan), accompanied by D.D. Bukinich and V.N. Lebedev.

Expedition to Khoresm (Khiva, Novyi Urgench, Gurlen, Tashauz).

Expedition to Mediterranean countries (France, Syria, Palestine, Transjordan, Algeria, Morocco, Tunisia, Greece, Sicily, Sardinia, Cyprus and Crete, Italy, Spain, Portugal, and Egypt, where Gudzoni was explored by Vavilov's request) and to Abyssinia (Djibouti, Addis Ababa, banks of Nile, Tsana Lake), Eritrea (Massaua) and Yemen (Hodeida, Jidda, Hedjas).

Exploration of mountainous regions in Wuertemberg (Bavaria, Germany).

Expedition to China (Xinjiang - Kashgar, Uch-Turfan, Aksu, Kucha, Urumchi, Kulja, Yarkand, Hotan) together with M.G. Popov, then alone to Chine (Taiwan), Japan (Honshu, Kyushu and Hokkaido) and Korea.

Expedition to USA (Florida, Louisiana, Arizona, Texas, California), Mexico, Guatemala and Honduras.

Trip to Canada (Ontario, Manitoba, Saskatchewan, Alberta, British Columbia), USA (Washington, Colorado, Montana, Kansas, Idaho, Louisiana, Arkansas, Arizona, California, Nebraska, Nevada, New Mexico, North and South Dakotas, Oklahoma, Oregon, Texas, Utah); Expedition to Cuba, Mexico (Yucatan), Ecuador (Cordilleras), Peru (Lake Titicaca, Puno Mt., Cordilleras), Bolivia (Cordilleras), Chile (Panama River). Brazil (Rio de Janeiro, Amazon), Argentina, Uruguay, Trinidad and Porto Rico.

Systematic explorations of the European part of Russia and the whole regions of the Caucasus and the Middle Asia.

(partially adapted from