Dos diseños rivales de bioquímica de plantas compiten por dominar el
mundo. Uno, llamado C3 por del número de átomos de carbono en los azúcares
iniciales que forma, es viejo, pero todavía dominante. El arroz es una planta
C3. El otro, llamado C4, es más nuevo en la historia evolutiva, y ahora cuenta
con alrededor de 21% del "mercado" de la fotosíntesis. El maíz es una
planta C4. Cuando hace calor, el mecanismo de C3 se vuelve ineficiente en la
absorción de dióxido de carbono del aire, pero en un clima fresco, C4 deja de
funcionar por completo. Por lo tanto, a primera vista parece como si el
calentamiento global debiera beneficiar a C4.
Sin dudas, a pleno sol y cálidas temperaturas, las plantas C4 crecen más
rápido que las C3 y necesitan menos fertilizante nitrogenado. En esas
condiciones, un cultivo C4 como el maíz o la caña de azúcar puede lograr un
mayor rendimiento y tolerar mejor las sequías que un grano como el trigo o el
arroz. De las 86 especies de plantas que suministran la mayor parte de los
alimentos del mundo, sólo un puñado son C4, pero dominan la agricultura
tropical: los principales son el maíz, la caña de azúcar, el mijo y el sorgo.
Sin embargo, no es tan sencillo. Sorprendentemente, la estrategia de C4
primero se volvió común en las repetidas edades de hielo que comenzaron hace cuatro
millones de años. Eso se debió a que las edades de hielo fueron una época muy
seca en los trópicos y los niveles de carbono eran muy bajos, cerca de la mitad
de los niveles actuales. Las plantas C4 son mejores en captar dióxido de
carbono (la fuente de carbono para los azúcares) del aire y desperdician mucha
menos agua al hacerlo. En cada período de frío glacial, los bosques dieron paso
a praderas estacionales en una gran escala. Sólo cerca de 4% de las especies de
plantas usan C4, pero casi la mitad de todos los pastos lo hacen, y estos que las C4. Cerca de 500 experimentos por separado confirman que, si
los niveles de dióxido de carbono se duplican desde los niveles
preindustriales, los rendimientos del arroz y el trigo crecerán en promedio 36%
y 33%, mientras que los del trigo se elevarán sólo 24%.
Otra complicación es que C4 tiene una participación mayor del mercado de
las malas hierbas. De las 18 malezas más pestilentes que perjudican a los
agricultores, 14 son C4. Por lo tanto, en igualdad de condiciones, y en
especial en regiones templadas donde dominan las C3, la batalla contra las
malezas debería ser más fácil a medida que aumentan los niveles de dióxido de
carbono, porque los cultivos C3 pueden acelerar su crecimiento más de lo que
pueden las malas hierbas C4.
El año pasado, Qing Zeng, del Instituto de Ciencia del Suelo, en
Nanjing, y sus colegas publicaron la primera prueba de esta predicción en una
granja real. Mediante la emisión de dióxido de carbono sobre las parcelas de
arroz, enriquecieron el aire a casi el doble del nivel ambiental de dióxido de
carbono. Luego midieron la tasa de crecimiento tanto del arroz como de la peor
maleza, la echinochloa, una planta herbácea de tipo C4, en las parcelas
experimentales, comparada con las parcelas de control cercanas.
El peso de las espigas de arroz mejoró en 37,6%, mientras que el
crecimiento de la echinochloa se redujo en realidad en 47,9%, debido a que el
vigoroso arroz proyectó sombra sobre las malas hierbas. Así, la buena noticia
es que, en general, el aumento de los niveles de dióxido de carbono ayuda un
poco a los cultivos (principalmente C3) que compiten con las malas hierbas
(sobre todo C4) y no al revés.
Sin embargo, esa enorme ventaja de rendimiento de las plantas C4 en
climas cálidos sugiere un obvio próximo objetivo para los cultivadores de
plantas.
Teniendo en cuenta que la mayor parte del arroz crece en los países
cálidos, jugar con sus genes para convertirlo en una planta C4 podría impulsar su
rendimiento en 50% y reducir su necesidad de nitrógeno, lo que transformaría el
suministro mundial de alimentos. Ese es el objetivo del C4 Rice Project, en el
Instituto Internacional de Investigación del Arroz en Filipinas. Está
entusiasmado por el hecho de que la "tecnología" C4 ha surgido de
forma natural en muchas líneas de plantas diferentes, así que ¿por qué no
meterla también en el arroz?
The caveman diet: Meat-eaters love it, critics call it ‘a craze’
By Randy Shore, Vancouver SunJuly 13, 2012
Our hunter-gatherer ancestors thrived on a daily menu of whatever was at hand until the development of agriculture about 10,000 years ago.
Photograph by: Vancouver Sun , Handout
Fruits, nuts, grass and whatever grubs, insects or game you can kill with your hands or a rock.
Our hunter-gatherer ancestors thrived on a daily menu of whatever was at hand until the development of agriculture about 10,000 years ago, and a surprising number of dieters and fitness buffs are turning back their dietary clocks.
In a nutshell, the paleodiet is an attempt to approximate the caloric and nutritional intake that human beings evolved to eat, before we started to plant grain and legumes for their easy, abundant, but largely empty, calories. Or so the theory goes.
The modern menu includes grass-fed meats, fruits, cooked and raw vegetables, wild fish and unprocessed oils such as olive or avocado. Wheat, dairy and legumes, such as beans and peanuts, are not allowed because they are relatively recent additions to the human menu. Some versions forbid added salt. Most people limit or eliminate alcohol.
“It’s really popular, at least half the people at my gym are eating something like the caveman diet,” said Cassandra Kruger, a trainer at Momentum Fitness in Vancouver. “It’s in the same vein as the South Beach and Atkins diet in that they don’t include any refined carbohydrates, so no grains, no sugar, no flour and no processed foods.”
Some nutritionists warn that low-carb diets carry potential health hazards from kidney stones and low blood pressure to calcium deficiency and osteoporosis.
Ultralow carb diets induce ketosis, a state in which the body burns fat for energy. You will lose weight, but it is not without risk.
Warehouse manager Rahim Khan of Langley started on the paleodiet just before his 27th birthday. He weighed 250 pounds, heavy for his 5-foot-11 frame.
“Less than a year later I hit my optimal weight of 173 pounds,”said Khan, who lost weight even as he cut back on his workouts. “I used to be in the gym three or four days a week and sometimes for two hours, now it’s 30 minutes and I’m out.”
Khan, his wife Liz and their three children all follow the paleodiet at home. Exceptions have to be made when the kids visit their grandparents, Khan laughed.
“I was skeptical at first,” said Liz, who admits feeling sick and lethargic for the first two weeks after the change. “But I feel so much better now, I didn’t even know how lousy I felt before.”
The Khans eat grass-fed beef, pork and chicken, usually the fattiest cuts they can find. Wheat in all its forms has disappeared, along with soy and corn. Dairy is confined to butter and small amounts of aged cheese.
Fruits and vegetables make up the balance of the plate, which Rahim says he usually fills twice at supper time. When their personal workload gets heavy, the Khans will add a sweet potato with butter for extra energy.
“I like to just call it my lifestyle, it’s the most logical way to eat,” Rahim said. “What I do is based on the feedback my body gives. When I feel good I know I’m doing the right things.”
The cavemen diet is an attractive weight-management program, because it is naturally low in calories and you are generally encouraged to eat whenever you are hungry. But the paleolithic menu probably has the most traction with people who have gluten sensitivity or celiac disease.
“Just look at how many people are eliminating gluten from their diet,” Kruger said.
Indeed, gluten-free foods are among the fastest growing product classes at the grocery store. And theceliacscene.com lists dozens of restaurants across Metro Vancouver that offer gluten-free meals.
Chilliwack mom Lori Wedel made some paleolithic adjustments to her entire family’s diet to address her and her daughter Eva’s gluten sensitivity.
“When Eva was three or four we started noticing that she was having trouble with her digestion,” said Wedel, a community support worker.
Gluten sensitivity can cause symptoms including constipation, diarrhea and abdominal pain.
“We decided we needed to investigate what might be the problem and we started to do an elimination diet,” she recalled.
Eva showed no change when dairy was removed from the menu. “But when we got to gluten it was completely different and rapidly different,” she said. “Within a week we noticed big changes, some we didn’t expect.”
“We thought she was a typical four-year-old until we started changing her diet,” Wedel said. “She was a terror with concentration problems and aggression, but once we started removing gluten it changed altogether.”
Wedel’s own allergies to nuts and to seafood meant there were few processed foods in the house anyway, but even fewer when the family began to eliminate sugar, artificial colourings and gluten.
“The difference in Eva made it impossible to go back,” Wedel said. “We can’t eat another way.”
Rather than keeping abundant carbohydrates in their diet with gluten-free breads and pasta, the Wedels just eliminated bread and grain-based foods such as pasta. At $7 a loaf for gluten-free bread, it just didn’t make sense.
“We eat meat every day and a whack of vegetables, usually in a stir-fry,” she said. “We don’t follow the strict paleodiet, if we have sushi we eat the rice and sometimes we have quinoa.”
Even though the Wedels don’t consider themselves paleodieters, Eva likes to joke that she is a caveman child. Lori’s husband Will, an engineer with the City of Chilliwack, is a big fan of the hefty portions of meat, usually chicken, pork and grass-fed beef.
“For me the biggest change was just deciding that not every meal had to be like my mom taught me, meat, potatoes, grain, you don’t need those to live,” she said.
Wedel’s sister Brittany Eidsness, a registered holistic nutritionist, helped tweak the family’s menus.
When calories from wheat, rice, potatoes and refined sugar are eliminated from the diet, the ratio of fibre, vitamins, minerals and important nutrients per calorie consumed goes way up.
The exception is vitamin D, which hunter gatherers produced in great abundance because they lived outdoors and spent long hours walking and foraging.
“People have a hard time figuring out what to eat and this diet is healthy and very clear,” she said. “It removes all of the foods that cause us problems.”
Proponents of the caveman diet point out that so-called “diseases of civilization” — heart disease, cancer, obesity and diabetes — were not a problem to people who lived in the Paleolithic period, which ran from about 2.5 million years ago until farming took hold about 8,000 BCE.
“The paleodiet is naturally low-carb and focuses on clean protein sources like grass-fed beef, wild fish, naturally raised chicken and eggs,” said Eidsness. “Then you are going to have as many vegetables as you can possibly eat, with the possible exception of nightshade vegetables for people who are sensitive to them.”
Stricter paleodieters avoid eating members of the nightshade family, which includes peppers, eggplant, tomatoes and potatoes, in the belief that they cause loss of calcium and may trigger arthritis or autoimmune disease.
People transitioning to the caveman diet can expect a minor rebellion by their body. Many people experience lethargy, headaches and flu-like symptoms that Eidsness attributes to a withdrawal from the body’s addiction to sugar and carbohydrates.
Critics of the paleodiet trend point to a long list of incongruities, knowledge gaps about the true nature of man’s diet during the Paleolithic period.
A true paleolithic diet would probably include some wild game, tart berries, insects, roots and wild tubers, shellfish, rodents and the occasional cache of honey. But it would also vary enormously from north to south, coast to inland and continent to continent, ranging from a chimpanzee-like diet of fruits to a very fatty meat-based diet of seal and caribou consumed by Arctic peoples.
The truth is that defining a true paleolithic diet is next to impossible.
What we do know is that the abundant calories of cultivated grain gave rise to a massive human population boom and gave birth to permanent sedentary civilization, both of which roil unabated to this day.
In addition to the potential for health impacts from eating an ultra low-carb diet, a leading Canadian nutritionist warns that paleodieters often eat more meat than is healthy for them and the planet.
The environmental cost of a largely meat-based diet is probably the strongest argument against eating like a modern caveman, said David Jenkins, a professor of nutritional sciences at the University of Toronto and Canada Research Chair in Nutrition and Metabolism.
“We just can’t produce enough calories in meat protein and fat to feed the world’s human population, it’s not sustainable,” Jenkins said.
Widely accepted estimates suggest it takes 16 kilos of grain to produce one kilo of beef and at least 441 gallons of water.
“The [caveman diet] craze is interesting in that it focuses on increased fibre foods, but people get bored of fibre if you can’t have it as bread or pasta or rice,” Jenkins said. “These are the starchy staples that allowed us to multiply on the face of the planet.”
Caveman diet proponents claim that eating what they believe to be the human ancestral diet will reduce their risk of disease, pointing out that Paleolithic era people were not afflicted with today’s most common ailments, many of which are associated with obesity and old age.
That idea might just hold water.
Pre-agricultural humans did live long enough to suffer from diseases of age and there is evidence arthritis was common, though obesity, heart disease and diabetes were rare or entirely absent.
Jenkins is skeptical that such dramatic alterations in our modern diet are key to better health.
“The first step in adopting a paleolithic lifestyle would be to throw away your car keys and walk everywhere,” he said. “The diet we have adopted over the past 10,000 years suits our physiology just fine if we are exercising. The problem is we put all these starchy calories in our body and then try to burn them driving everywhere in our cars.”
Investigadores del Cinvestav buscan entender el mecanismo de olfato de las plantas para aprovecharlo en la agricultura en sustitución de alternativas químicas
Oler provee a las plantas de un “sistema de protección” que les permite preparase contra amenazas futuras. (Foto: Archivo El Universal )
Comúnmente se cree que sólo los humanos y los animales poseen la capacidad de comunicarse y del olfato; sin embargo, reciente investigaciones comprobaron que las plantas también poseen estas cualidades, incluso son capaces a través del olfato, advertir amenazas como plagas.
Sarai Girón Calva, científica adscrita al Centro de Investigación y de Estudios Avanzados (Cinvestav) Unidad Irapuato afirmó que las plantas poseen la capacidad de oler, y a pesar de que aún se desconoce el mecanismo de percepción, se sabe que la utilizan para defenderse de plagas que han invadido a plantas vecinas.
Las plantas, dijo, utilizan su olfato para comunicarse, tienen un "lenguaje", y al entenderlo es posible obtener muchos beneficios, principalmente a nivel agrícola que servirían de alternativas a los químicos usados comúnmente para proteger a las plantas de plagas.
Es importante mencionar que estos compuestos volátiles son emitidos de manera natural por las plantas y a las concentraciones usadas no representarían un riesgo para los cultivos, el ambiente o las personas, aclaró Girón Calva.
Aparte de amenazas las plantas comunican a sus vecinas acerca de: cambios en la intensidad de luz, humedad, temperatura, la presencia de plantas parásitas o plantas de la misma especie.
La investigadora quien realiza un estudio acerca del olfato de las plantas y su forma de comunicación, precisó que aunque podríamos considerar a las plantas débiles por ser organismos inmóviles, oler provee a las plantas de un "sistema de protección" que les permite preparase de antemano para responder de una manera más robusta a futuras amenazas y así poder cumplir su ciclo.
Para evitar desperdiciar sus defensas en una guerra inexistente las plantas poseen un estado fisiológico llamado priming, en el que sus defensas no están totalmente inducidas, sino a la espera de un estimulo que confirme la presencia del enemigo para inducirse totalmente a su estado de defensa.
Entender como funciona el olfato de las plantas puede proporcionar alternativas al uso de bactericidas u otros químicos empleados para tratar patógenos, reveló Sarai Girón Calva. "Se podría colocar una planta que emitiera volátiles cada cierta distancia para inducir resistencia en plantas vecinas o bien se podrían exponer los cultivos a una determinada concentración de volátiles sintéticos".
Los estudios de la científica del Cinvestav consisten en exponer plantas de frijol lima a diversas concentraciones de los compuestos orgánicos volátiles por diferentes períodos de tiempo. Posteriormente las plantas son expuestas a una bacteria, para proceder a evaluar la resistencia inducida de la planta.
Con la investigación realizada en Cinvestav se amplió el conocimiento existente acerca del olfato de las plantas, dijo Girón Calva, "ahora sabemos que hay un umbral de concentración que las plantas necesitan oler y alcanzar dicho umbral está en función de la concentración del compuesto volátil en la atmósfera y del tiempo en que las plantas están expuestas a él".
El proyecto, con duración de un año y medio, se realizó en los invernaderos y el laboratorio de Ecología de Plantas del Cinvestav Unidad Irapuato, donde contó con la supervisión de Martin Heil, investigador de la misma unidad.
Acerca de investigaciones posteriores sobre el olfato de las plantas Sarai Girón comentó estar interesada en saber por qué las plantas no responden a todos los compuestos presentes en el bouquet emitido, el impacto directo que factores ambientales tiene en esta señalización y cómo es el mecanismo de percepción.
New innovations in agriculture for Moroccan researchers
Hesbris-GTA
Thursday 10 may 2012-10: 35
Invented by researchers from University of Meknes Moulay Ismail new techniques for measuring the quality of milk and fertilizer development العضويه٬ which would contribute to the development of agricultural production.
The Rector said Ahmed albrihi told Arab Morocco للانباء٬ innovation first international patent registered on behalf of the University and is an electromagnetic sensor can be quick and accurate measurement of the quality of الحليب٬ as well as to know the proportion of water and materials it contains.
Innovation الثاني٬ which got through the University first prize Ismaël for innovation in farming international exhibition events recently organised بمكناس٬ is the fertilizer عضويه٬, dubbed the "articles of the future".
Article consists of these الاسمده٬ as initial البريهي٬ of useful micro organisms of plant growth without مخاطر٬ so as to enable such authors to achieve the original formulation of this material which can be used to reduce the use of certain fertilizers which threaten human life.
The authors of this type of fertiliser managed to harness the dynamic objects in the service of humanity, believing that "bacteria graduated from Earth and to return."
He noted that this innovation is assumed to provide highly effective materials has been accessed taking care to be "environmentally friendly" has been accessed which translates the University logo (University innovate for sustainable farming).
The four were among these types of innovative international exhibition almsmedat للفلاحه٬ used in the cultivation of vegetables and fruit trees, as well as for the benefit of forest trees and major field crops.
The University has signed regarding اسماعيل٬ Moulay الابتكارين٬ four تعاون٬ conventions, including Conventions Nos. اطار٬ and two concrete with large domain into specializing in agriculture.
These agreements concern supported by the Ministry and the Association for research and development بالمغرب٬ research cooperation projects and strengthening of relations between enterprises and universities in Morocco
