Some Lupinus species produce cluster roots in response to low plant phosphorus (P) status. Wang et al. measure relative growth rate (RGR) among three lupin species, L. albus, L. pilosus and L. atlanticus, with similar shoot P status and find that cluster-root formation is suppressed at high leaf P concentration, irrespective of RGR. Variation in cluster-root formation among these species cannot be explained by species-specific variation in RGR or leaf P concentration. This goes against the expectation that, even when P-uptake rates are high, plants with fast growth rates might not accumulate shoot P and hence a correlation between RGR and cluster-root formation could be anticipated.
In citrus the juvenile phase can last 5–20 years depending on the variety, which is a serious constraint for molecular and conventional breeding. Castillo et al. screen juvenile and adult Citrus sinensis and C. jambhiri to identify differentially expressed transcription factors, and incorporate data from C. reticulat × C. sinensis and C. paradisi in order to select genes with phase-specific regulation common to all four species. Some of the identified genes are MADS-box genes, whereas the others show high partial sequence similarity restricted to specific domains but negligible outside those domains, suggesting that they might be novel genes that play specific roles during the juvenile-to-adult transition in citrus.
The March 2013 issue of Annals of Botany is now Free Access. The cover image is of two generations of moss, the younger sporophytes growing from the parent gametophyte. AJ Cann blogged about this paper last year.
If you get confused between sporophytes and gametophytes, then you’re not alone. Plants alternate generations between sporophytes and gametophytes. The children of oak trees aren’t acorns, they’re grandchildren. The ‘children’ of oaks would be pollen and the embryo sacs they pollinate. Contrary to popular belief pollen isn’t plant sperm.
Kevin Folta has put up a thought-provoking post on his blog, Illumination. There’s been a flurry of news stories around a new research paper that shows a Round-Up, Monsanto’s herbicide, in rain. A closer look at the paper reveals that’s not quite the story.
What the research shows is there are chemicals in very low concentrations that are consistent with Round-Up. This might seem like pedantry, but it’s important pedantry because the same tests show a reduction in other chemicals associated with more harmful herbicides and pesticides between 1995 and 2007. It’s consistent with Round-Up and GM crops being ecologically safer.
There is room for debate. The fields were different crops in different places so it depends what standard of proof you want. What the paper does show is that chemicals are not-trivial additions to an environment and in some cases have a long-term presence.
Kevin’s post on the paper also shows access to papers is important. The original paper is here, but unless you’re at a university with a subscription, you might have trouble getting it. In a perfect world all papers would be Open Access, and for AoB, all papers in AoB Plants and this month Annals of Botany has three open access papers. Access to subscription papers is more difficult. In our case papers in Annals of Botany become free access after a year, but that’s a long time to wait.
For press releases we have a policy that if we put out a press release for a paper, we make the paper free access to anyone can compare the release to what is actually in the paper if they want. However, we can’t do this for every paper. We do have a limited marketing budget though. If there is interest in a paper and we see it get blogged in a couple of places we’ll do what we can to make it free access.
As always, if a blogger wants access to a paper behind a paywall then contact me and I’ll get a copy so you can write about more than just the abstract.
Or you can do what Kevin Folta, and no one else did, and contact the author.
Three men sitting in deck chairs, smoking pipes and reading newspapers by John Henry Harvey. Courtesy of the State Library of Victoria, Asutralia.
Non-S-ribonucleases (non-S-RNases) are class III T2 RNases expressed in the styles of species exhibiting S-RNase-based self-incompatibility (SI). So far, no role has been attributed to these RNases, which are not functional in the SI system. By combining RT-PCR, immunoblot and enzymatic activity approaches, Rojas et al. demonstrate that NnSR1 (Nicotiana non-S-RNase1) is induced in roots of Nicotiana alata subjected to phosphate deprivation, resembling the functionality of phylogenetically divergent class I and class II S-like RNases. NnSR1 appears to have regained ancestral functions of class III RNases related to strategies to cope with phosphate limitation and possibly with other environmental challenges.
Isoprene is the most important volatile organic compound (VOC) emitted by plants. Morfopoulos et al. hypothesize that NADPH availability for isoprene biosynthesis depends on the balance of electron supply and Calvin cycle demand. A simple model based on this hypothesis explains many features of the observed response of isoprene emissions to environmental factors. The decoupling between carbon assimilation and isoprene emission (e.g. opposite responses to CO2) is accounted for, whereas previous models resorted to empirical corrections. This work suggests a way forward to global-scale VOC emission models that will be both simpler, and more robust, than those currently favoured.
There is a widespread belief that everything in/of/from/about America is bigger, better, faster, etc, than anything from elsewhere in the world. That is probably the best example of spin over substance ever foisted on an unsuspecting world, and is a true testament to the power of marketing and public relations.
Take, for example, the arresting title ‘This Could Be the Oldest Flowering Plant Ever Found in North America’. So prevalent is that view of American supremacy and so conditioned are we to its acceptance that many of us will have read that text and mentally added a comma after the words ‘ever found’ (and the importance of comma placement is legendary). The news story concerns a re-assessment of fossil plants stored away in the USA’s Smithsonian National Museum of Natural History. Originally thought to be a fern, reinspection and analysis by USA-based Nathan Jud and Leo Hickey now confirms that the fossil is an angiosperm (a flowering plant) between 125 and 115 million years old (Ma) – the Lower Cretaceous – named Potomacapnos apeleutheron.
While this is amongst the oldest flowering plants found in America, it is not the oldest known on Earth. That honour goes – currently! – to the unnamed bearers of ‘angiosperm-like pollen’ and the described genus Afropollis from Middle Triassic deposits in Switzerland that are 247.2–242.0 Ma, as unearthed by Peter Hochuli and Susanne Feist-Burkhardt. The pollen was studied using confocal laser scanning microscopy (CLSM), exploiting the autofluorescence still present in such ancient organic-walled microfossils. Quite dramatically, this announcement pushes back the origin of flowering plants another 100 Ma into history, which must be rather gratifying for the Swiss–German team. So, whilst national self-belief is a good thing to have (rather like patriotism), it mustn’t blind us to the fact that other countries may have more legitimate claims to ‘biggest and best’ (and which might stray into nationalism). And anyway, it’s only because of ‘accidents of history, geography and politics’ that scientific discoveries are tied to a particular place and claimed for, and/or by, individual countries. Science – and its discoveries – belongs to us all. There, I’ve said it (and with flowers…).
[As usual, Mr Cuttings has tried to be a little mischievous in this item. But it probably won’t halt the activities of those whose lifelong goal is to seek out the biggest, best, etc, so expect further archaefloral revelations from the good old US of A in due course (and maybe further afield…), as more store-rooms replete with rocky riches are rummaged through, re-examined, and re-assessed! And if a good bit of healthy, old-fashioned competition and rivalry can spur on all those engaged in the process of science to even greater things, then so much the better – for us all! – Ed.]
Perhaps you enjoy solving jigsaw puzzles. Have you heard about living jigsaw puzzles? Imagine such a puzzle in which the individual pieces were not static but they were continuously changing. So, you will need to assemble it, at the same time as the pieces are growing and changing shape. This might sounds weird. But, actually among plant curiosities, there are some cells that have just this curious morphology resembling a jigsaw-like puzzle shape (left). These cells are called pavement cells and together with stomata coexist in the epidermis of leaves of many species.
They start their development as simple geometrical shapes, such as rectangles or hexagons and over time, they acquire their characteristic jigsaw-like shape, alternating with lobes (protrusions) and indentations. Then, the leaf is exactly like a puzzle which pieces are growing and changing shape over time: an alive puzzle!
How do they get their shape? This is a very intriguing question that continues puzzling plant scientists. On one hand, there is the question of patterning inside a cell, that is, how a cell creates the asymmetries that later on will become a lobe and indentation. Moreover, the decision to make lobes and indentations needs to be coordinated with their neighbours; otherwise, the whole puzzle will fall apart! This actually happen in some plant mutants whose cells fail to develop correct lobes and indentations, and as a consequence, their leaves have some holes in between.
Later, once these regions have been specified, the lobes and indentations develop. Then, the other side of the question on how they get their shapes is how these regions growth differentially to create lobes alternated with indentations. Elsner et al., 2012, studied the shape acquisition of these cells using the replica method. This technique consists of creating impressions of the epidermis during different days, so that the same cells are followed over time. It is like in order to know how the pieces of our hypothetical puzzle are changing shape, we decided to take pictures at different times. Interestingly, they found that the peculiar geometry of these cells could come about because different segments of the future pavement cells growth differentially and because they appear at different times. Then, it would be like if the sides of each of the pieces of our puzzle were growing differentially and were appearing at different times as well. How this is regulated remains a mystery.
Another fact that adds interest to our living-puzzle is that these cells get their jigsaw-like shape in a very stereotyped manner within the leaf. In Arabidopsis thaliana and Nicotiana bentamiana, cells acquire their shape first at the tip of the leaf and over time, cells at the base also show a jigsaw-like shape. So, the pieces of our puzzle are getting their shape first at one extreme and, over time, towards the other extreme. This situation resembles a famous picture by the Dutch painter M.C. Escher, called Metamorphosis (above), where the pieces are more complex towards one extreme. Enigmatic questions around the spatial development of pavement cells are: how is this pattern of cell morphogenesis from the tip to the base controlled? Is it similar in other species? Is this important for overall leaf shape?
Another puzzling question is what are they for. Perhaps the interdigitating pattern helps the leaves to be more resistant to breakage. Perhaps they increase the contact area with neighbours and cells can communicate faster. These possibilities are, of course, just speculations.
A very interesting observation is that these cells have quite different jigsaw-shape depending on the plant species. In fact, the pavement cells of several plants range from simple pieces to a very complex pieces, varying in their degree (or amplitude) of their lobes, the spacing (periodicity) between them, the elongation, etcetera (right). Just as there are jigsaw puzzles with different degree of difficulty!
Although a changing jigsaw puzzle sounds a lot of fun, at the moment it is just an idea. What we have are the pavement cells, our living puzzles, whose shape embrace very interesting questions to continue puzzling us for a while!
Quizá te gusta resolver rompecabezas. ¿Has escuchado alguna vez sobre rompecabezas vivientes? Imagina un rompecabezas donde las piezas no permanecieran fijas sino que cambiaran constantemente. Lo tendrías que resolver al mismo tiempo que las piezas estuvieran creciendo y cambiando forma. Tal vez suena extraño. Sin embargo, entre las curiosidades de las plantas existen células que tienen precisamente la forma de piezas de rompecabezas (Fig). Estas células epidérmicas junto con los estomas se encuentran en la epidermis de las hojas de muchas especies.
Empiezan su desarrollo teniendo una forma simple, por ejemplo rectangular o hexagonal y, a través del tiempo, adquieren su forma característica de piezas de rompecabezas, alternando entre ondulaciones y depresiones de su membrana. Entonces, las hojas son exactamente como un rompecabezas cuyas piezas están creciendo y cambiando forma a través del tiempo: ¡un rompecabezas viviente!
¿Cómo es que adquieren su forma? Esta es una pregunta muy interesante que continua siendo un misterio para los científicos que estudian plantas. Por un lado está la pregunta de cómo la célula crea diferentes regiones dentro de sí misma de tal manera que, después éstas se convertirán en ondulaciones y depresiones. Además, la decisión de especificar estas regiones necesita coordinarse con las células vecinas; de otra manera, ¡todo el rompecabezas se caería en pedazos! Esto se ha observado en algunos mutantes en los que las células no desarrollan ondulaciones correctamente, y como consecuencia, sus hojas tienen hoyos.
Una vez que las regiones que corresponden a ondulaciones o depresiones de la membrana han sido especificadas, las células empiezan a adquirir su forma. Entonces, la otra pregunta es como estas regiones crecen de manera diferente para adquirir la forma de piezas de rompecabezas. Elsner et al., 2012 estudiaron como estas células adquieren su forma usando el método llamado replicas. Esta técnica requiere hacer impresiones de la epidermis de la hoja por varios días, de tal manera que las mismas células se puedan seguir a través del tiempo. Es como si para saber cómo cambian las piezas de nuestro rompecabezas, decidiéramos tomarles fotografías todos los días. Elsner y sus colegas encontraron que la singular forma de estas células podría explicarse porque segmentos dentro de la célula crecen de manera diferente y también porque las ondulaciones no aparecen al mismo tiempo. Entonces, podría ser como si los lados de nuestras piezas de rompecabezas crecieran de manera distinta y también aparecieran en diferentes momentos. Cómo este proceso es regulado es todavía un misterio.
Otro dato curioso que le agrega interés a nuestro rompecabezas viviente es que estas células adquieren su forma de una manera estereotípica dentro de la hoja. En Arabidopsis thaliana y Nicotiana bentamiana, las células adquieren su forma primero en el punta de la hoja y a través del tiempo, también se pueden observar en la base. Es decir, las piezas de nuestro rompecabezas adquieren primero su forma en un extremo de la hoja y después, en el otro extremo. Esta situación se parece a la pintura del pintor holandés M.C. Escher, llamada metamorfosis (Fig). Algunos misterios sobre la regulación espacial de la morfogénesis de estas células son: ¿cómo se controla este patrón desde la punta hacia el petiolo? ¿Es similar en otras especies? ¿Es importante para la forma de toda la hoja?
Otra inquietante pregunta es para qué sirven estas células. Quizá el patrón de interdigitacion ayuda a las hojas a ser más resistentes a romperse. A lo mejor su forma ayuda a incrementar el área de contacto con sus vecinas y así, las células se pueden comunicar más rápido. Estas posibilidades son, por supuesto, solo especulaciones.
Una observación muy interesante es que estas células tienen diferente forma de piezas de rompecabezas dependiendo de la especie. De hecho, células de la epidermis de diferentes plantas van desde formas muy simples hasta formas muy complejas, variando en su grado o amplitud de sus protusiones, el espacio entre ellas, etcétera (Fig). ¡Así cómo existen rompecabezas con distinto grado de dificultad!
Aunque un rompecabezas que cambia forma suena muy divertido, al momento es solo una idea. Lo que tenemos ahora son las células de la epidermis, nuestros rompecabezas vivos, cuya forma encierra preguntas muy interesantes que ¡nos continuaran intrigando por un tiempo!