Marcos Yanniccari

Frequently asked questions about in vivo chlorophyll fluorescence: practical issues

The aim of this educational review is to provide practical information on the hardware, methodology, and the hands on application of chlorophyll (Chl) a fluorescence technology. We present the paper in a question and answer format like frequently asked questions. Although nearly all information on the application of Chl a fluorescence can be found in the literature, it is not always easily accessible. This paper is primarily aimed at scientists who have some experience with the application of Chl a fluorescence but are still in the process of discovering what it all means and how it can be used. Topics discussed are (among other things) the kind of information that can be obtained using different fluorescence techniques, the interpretation of Chl a fluorescence signals, specific applications of these techniques, and practical advice on different subjects, such as on the length of dark adaptation before measurement of the Chl a fluorescence transient. The paper also provides the physiological background for some of the applied procedures. It also serves as a source of reference for experienced scientists.

Glyphosate effects on gas exchange and chlorophyll fluorescence responses of two Lolium perenne L. biotypes with differential herbicide sensitivity.

Despite the extensive use of glyphosate, how it alters the physiology and metabolism of plants is still unclear. Photosynthesis is not regarded to be a primary inhibitory target of glyphosate, but it has been reported to be affected by this herbicide. The aim of the current research was to determine the effects of glyphosate on the light and dark reactions of photosynthesis by comparing glyphosate-susceptible and glyphosate-resistant Lolium perenne biotypes. After glyphosate treatment, accumulation of reduced carbohydrates occurred before a decrease in gas exchange. Stomatal conductance and CO(2) assimilation were reduced earlier than chlorophyll fluorescence and the amount of chlorophyll in susceptible plants. In the glyphosate-resistant biotype, stomatal conductance was the only parameter slightly affected only 5 days post-application. In susceptible plants, the initial glyphosate effects on gas exchange could be a response to a feedback regulation of photosynthesis. Since the herbicide affects actively growing tissues regardless of the inhibition of photosynthesis, the demand of assimilates decreased and consequently induced an accumulation of carbohydrates in leaves. We concluded that stomatal conductance could be a very sensitive parameter to assess both the susceptibility/resistance to glyphosate before the phytotoxic symptoms become evident.

Glyphosate Resistance in Perennial Ryegrass (Lolium perenne L.) is Associated with a Fitness Penalty

Abstract The net selection effect of herbicides on herbicide-resistance traits in weeds is conditioned by the fitness benefits and costs associated with resistance alleles. Fitness costs play an important evolutionary role preventing the fixation of adaptive alleles and contributing to the maintenance of genetic polymorphisms within populations. Glyphosate is widely used in world agriculture, which has led to the evolution of widespread glyphosate resistance in many weed species. The fitness of glyphosate-resistant and -susceptible perennial ryegrass plants selected from within a single population were studied in two field experiments conducted during 2011 and 2012 under different soil water availability. Glyphosate-resistant plants showed a reduction in height of 12 and 16%, leaf blade area of 16 and 33%, shoot biomass of 45 and 55%, seed number of 33 and 53%, and total seed mass of 16 and 5% compared to glyphosate-susceptible plants in 2011 and 2012, respectively. The reduction in seed number per plant resulted in a 40% fitness cost associated with the glyphosate-resistance trait in perennial ryegrass. Fitness costs of glyphosate-resistant plants were expressed under both conditions of water availability. These results could be useful for designing management strategies and exploiting the reduced glyphosate-resistant perennial ryegrass fitness in the absence of glyphosate selection. Nomenclature: Glyphosate; perennial ryegrass, Lolium perenne L., LOLPE.

Efecto del glifosato sobre el crecimiento y acumulación de azúcares libres en dos biotipos de lolium perenne de distinta sensibilidad al herbicida

El movimiento sistemico del glifosato esta determinado por el transporte de fotoasimilados. A su vez, la capacidad de un destino de consumir los asimilados esta condicionada por su actividad metabolica. Pese a su importancia, la relacion entre el glifosato y la sintesis de azucares en hojas fuente ha sido poco abordada. El objetivo del presente trabajo fue evaluar los efectos del glifosato sobre el crecimiento y la acumulacion de azucares libres en dos biotipos de Lolium perenne de baja y alta sensibilidad al herbicida. Se trabajo con clones de ambos tipos de plantas, en macollaje, tratados con 1.440 g e.a. ha-1 de glifosato y sin tratamiento herbicida como controles. Se evaluo periodicamente el efecto del glifosato sobre el rebrote de hojas hasta las 50 horas post-aplicacion y sobre los niveles de azucares libres totales, reductores y no reductores en hojas a 1, 2, 3 y 5 dias post-aplicacion. A partir de las 25 horas post-aplicacion, el glifosato provoco una disminucion del crecimiento del 58% en el biotipo susceptible, con una acumulacion de azucares libres superior al 90% con relacion al control, desde el primer dia post-aplicacion en adelante. La inhibicion del crecimiento, inducida por el glifosato en plantas susceptibles, no depende de la limitacion del traslado de fotoasimilados desde la parte aerea. Por tanto, la acumulacion de azucares libres en hojas podria explicarse por la caida en la tasa de crecimiento. En el biotipo de baja sensibilidad, en el que no se detecto inhibicion del crecimiento, estos efectos fueron limitados.

Erratum to: Frequently asked questions about chlorophyll fluorescence, the sequel

Hazem M. Kalaji1 · Gert Schansker2 · Marian Brestic3 · Filippo Bussotti4 · Angeles Calatayud5 · Lorenzo Ferroni6 · Vasilij Goltsev7 · Lucia Guidi8 · Anjana Jajoo9 · Pengmin Li10 · Pasquale Losciale11 · Vinod K. Mishra12 · Amarendra N. Misra13 · Sergio G. Nebauer14 · Simonetta Pancaldi6 · Consuelo Penella5 · Martina Pollastrini4 · Kancherla Suresh15 · Eduardo Tambussi16 · Marcos Yanniccari16 · Marek Zivcak3 · Magdalena D. Cetner1 · Izabela A. Samborska1 · Alexandrina Stirbet17 · Katarina Olsovska18 · Kristyna Kunderlikova18 · Henry Shelonzek19 · Szymon Rusinowski20 · Wojciech Bąba21