Botânica, o que há em um nome?

The recent emergence of new biological disciplines, e.g., Molecular Biology, has created tensions with previously established fields of biological inquiry. Regarding plants as subject matter, the term Plant Biology is increasingly being used instead of Botany, and this brings new levels of organization into focus. In this article I intend to give a few relevant examples of the knowledge provided by the addition of cell and molecular biology approaches to the study of plants, and I will advocate for a deeper integration of plant studies at different levels of organization.La emergencia reciente de nuevas áreas de investigación biológica, como por ejemplo la Biología Molecular, ha introducido tensiones con las disciplinas establecidas desde hace más tiempo. En referencia estricta a las plantas como objeto de estudio, Biología Vegetal parece encaminarse a remplazar al término Botánica, agregando al estudio de los organismos vegetales nuevos niveles de organización (v.g., celular, molecular). En este artículo me propongo dar algunos ejemplos relevantes sobre los aportes derivados de la incorporación de los enfoques celulares y moleculares al conocimiento sobre las plantas, e intentaré abogar por una mayor integración entre los estudios en distintos niveles de organización biológica.O surgimento recente de novas áreas de pesquisa biológica, como por exemplo a Biologia Molecular, introduziu tensões com disciplinas estabelecidas há mais tempo. Em referência estrita às plantas como objeto de estudo, Biologia Vegetal parece encaminhar-se a substituir o termo Botânica, acrescentando ao estudo dos organismos vegetais novos níveis de organização (por exemplo, celular, molecular). Neste artigo, pretendo dar alguns exemplos relevantes das contribuições derivadas da incorporação dos enfoques celulares e moleculares ao conhecimento sobre as plantas, e tentarei defender uma maior integração entre os estudos em diferentes níveis de organização biológica

Botânica, o que há em um nome?

La emergencia reciente de nuevas áreas de investigación biológica, como por ejemplo la Biología Molecular, ha introducido tensiones con las disciplinas establecidas desde hace más tiempo. En referencia estricta a las plantas como objeto de estudio, Biología Vegetal parece encaminarse a remplazar al término Botánica, agregando al estudio de los organismos vegetales nuevos niveles de organización (v.g., celular, molecular). En este artículo me propongo dar algunos ejemplos relevantes sobre los aportes derivados de la incorporación de los enfoques celulares y moleculares al conocimiento sobre las plantas, e intentaré abogar por una mayor integración entre los estudios en distintos niveles de organización biológica.The recent emergence of new biological disciplines, e.g., Molecular Biology, has created tensions with previously established fields of biological inquiry. Regarding plants as subject matter, the term Plant Biology is increasingly being used instead of Botany, and this brings new levels of organization into focus. In this article I intend to give a few relevant examples of the knowledge provided by the addition of cell and molecular biology approaches to the study of plants, and I will advocate for a deeper integration of plant studies at different levels of organization.O surgimento recente de novas áreas de pesquisa biológica, como por exemplo a Biologia Molecular, introduziu tensões com disciplinas estabelecidas há mais tempo. Em referência estrita às plantas como objeto de estudo, Biologia Vegetal parece encaminhar-se a substituir o termo Botânica, acrescentando ao estudo dos organismos vegetais novos níveis de organização (por exemplo, celular, molecular). Neste artigo, pretendo dar alguns exemplos relevantes das contribuições derivadas da incorporação dos enfoques celulares e moleculares ao conhecimento sobre as plantas, e tentarei defender uma maior integração entre os estudos em diferentes níveis de organização biológica.Facultad de Ciencias Naturales y Muse

The stay green mutations d1 and d2 increase water stress susceptibility in soybeans

The stay green mutant genotype d1d1d2d2 inhibits the breakdown of chloroplast components in senescing leaves of soybean (Glycine max L. Merr.). Together with G (a gene that preserves chlorophyll in the seed coat) they may extend photosynthetic activity in some conditions. While wild-type soybeans maintain high leaf water potentials right up to abscission, leaves of (GG)d1d1d2d2 dehydrate late in senescence, which suggests that water relations may be altered in the mutant. Three-week-old plants were subjected to a moderate water deficit (soil water potential=-0.7 MPa) for 7-10 d. Leaf water potential and relative water content decreased significantly more in response to water deficit in unifoliate leaves of GGd1d1d2d2 than in a near-isogenic wild-type line. Down-regulation of stomatal conductance in response to drought was similar in mutant and wild-type leaves. Likewise, exogenously applied ABA reduced stomatal conductance to a similar extent in the mutant and the wild type, and applied ABA failed to restore water deficit tolerance in GGd1d1d2d2. Experiments with explants lacking roots indicate that the accelerated dehydration of GGd1d1d2d2 is probably not due to alterations in the roots. In a comparison of near-isogenic lines carrying different combinations of d1, d2 and G, only d1d1d2d2 and GGd1d1d2d2 (i.e. the genotypes that cause the stay green phenotype) were more susceptible to water deficit than the wild type. These data suggest that pathways involved in chloroplast disassembly and in the regulation of stress responses may be intertwined and controlled by the same factors.Instituto de Fisiología Vegeta

The stay green mutations d1 and d2 increase water stress susceptibility in soybeans

The stay green mutant genotype d1d1d2d2 inhibits the breakdown of chloroplast components in senescing leaves of soybean (Glycine max L. Merr.). Together with G (a gene that preserves chlorophyll in the seed coat) they may extend photosynthetic activity in some conditions. While wild-type soybeans maintain high leaf water potentials right up to abscission, leaves of (GG)d1d1d2d2 dehydrate late in senescence, which suggests that water relations may be altered in the mutant. Three-week-old plants were subjected to a moderate water deficit (soil water potential=-0.7 MPa) for 7-10 d. Leaf water potential and relative water content decreased significantly more in response to water deficit in unifoliate leaves of GGd1d1d2d2 than in a near-isogenic wild-type line. Down-regulation of stomatal conductance in response to drought was similar in mutant and wild-type leaves. Likewise, exogenously applied ABA reduced stomatal conductance to a similar extent in the mutant and the wild type, and applied ABA failed to restore water deficit tolerance in GGd1d1d2d2. Experiments with explants lacking roots indicate that the accelerated dehydration of GGd1d1d2d2 is probably not due to alterations in the roots. In a comparison of near-isogenic lines carrying different combinations of d1, d2 and G, only d1d1d2d2 and GGd1d1d2d2 (i.e. the genotypes that cause the stay green phenotype) were more susceptible to water deficit than the wild type. These data suggest that pathways involved in chloroplast disassembly and in the regulation of stress responses may be intertwined and controlled by the same factors.Instituto de Fisiología Vegeta

Plant–pathogen interactions: Leaf physiology alterations in poplars infected with rust (Melampsora medusae)

Rust produced by Melampsora sp. is considered one of the most relevant diseases in poplar plantations. Growth reduction in poplar plantations takes place because rust, like other pathogens, alters leaf physiology. There is not a complete evaluation of several of the physiological traits that can be affected by rust at leaf level. Therefore, the aim of this work was to evaluate, in an integrative way and in the same pathosystem, which physiological processes are affected when Populus deltoides Bartr. ex Marsh. leaves are infected by rust (Melampsora medusae Thümen). Leaves of two clones with different susceptibility to rust were analyzed. Field and pot experiments were performed, and several physiological traits were measured in healthy and infected leaves. We conclude that rust affects leaf mesophyll integrity, and so water movement in the leaf in liquid phase is affected. As a consequence, gas exchange is reduced, affecting both carbon fixation and transpiration. However, there is an increase in respiration rate, probably due to plant and fungal respiration. The increase in respiration rate is important in the reduction of net photosynthetic rate, but also some damage in the photosynthetic apparatus limits leaf capacity to fix carbon. The decrease in chlorophyll content would start later and seems not to explain the reduction in net photosynthetic rate. Both clones, although they have different susceptibility to rust, are affected in the same physiological mechanisms.Fil: Gortari, Fermin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Fisiología Vegetal. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Instituto de Fisiología Vegetal; Argentina. Universidad Nacional de Misiones. Facultad de Ciencias Forestales; ArgentinaFil: Guiamet, Juan José. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Fisiología Vegetal. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Instituto de Fisiología Vegetal; ArgentinaFil: Graciano, Corina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Fisiología Vegetal. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Instituto de Fisiología Vegetal; Argentina. Universidad Nacional de Misiones. Facultad de Ciencias Forestales; Argentin

Leaf gas exchange and competitive ability of Zea mays and Sorghum halepense as affected by water competition

In an environment involving water deficit and competition, weed species may show inefficient water use. The aim was to determine the water consumption strategy of Zea mays and Sorghum halepense and the effects of these strategies on crop and weed competitive ability.Under two soil water availability conditions, the soil and leaf water potential (Ψ), relative water content (RWC) and leaf gas exchange parameters were measured during the critical period of crop competition in pot experiments where Z. mays and S. halepense were grown alone or in competition. In addition, the relative yield total and aggressivity index of both species were calculated.S. halepense showed continuous absorption of water, reaching a lower Ψ than the Z. mays hybrids. S. halepense maintained a RWC of above 90%, which only decreased to 70% in the case of competition for low water supplies. In Z. mays, RWC declined to values of 70% at both water levels. S. halepense exhibited active leaf gas exchange. Z. mays hybrids had lower competitive ability than S. halepense at both competition levels due to their conservative water use strategy. Sustained water use by the weed could be the cause of the increased aggressivity of S. halepense under water deficit conditions.Facultad de Ciencias Agrarias y Forestale

Leaf gas exchange and competitive ability of Zea mays and Sorghum halepense as affected by water competition

In an environment involving water deficit and competition, weed species may show inefficient water use. The aim was to determine the water consumption strategy of Zea mays and Sorghum halepense and the effects of these strategies on crop and weed competitive ability.Under two soil water availability conditions, the soil and leaf water potential (Ψ), relative water content (RWC) and leaf gas exchange parameters were measured during the critical period of crop competition in pot experiments where Z. mays and S. halepense were grown alone or in competition. In addition, the relative yield total and aggressivity index of both species were calculated.S. halepense showed continuous absorption of water, reaching a lower Ψ than the Z. mays hybrids. S. halepense maintained a RWC of above 90%, which only decreased to 70% in the case of competition for low water supplies. In Z. mays, RWC declined to values of 70% at both water levels. S. halepense exhibited active leaf gas exchange. Z. mays hybrids had lower competitive ability than S. halepense at both competition levels due to their conservative water use strategy. Sustained water use by the weed could be the cause of the increased aggressivity of S. halepense under water deficit conditions.Facultad de Ciencias Agrarias y Forestale

Poplar leaf rust reduces dry mass accumulation and internal nitrogen recycling more markedly under low soil nitrogen availability, and decreases growth in the following spring

Rust is one of the most important biotic stress factors that affect poplars. The aims of this work were: (i) to analyze the changes in growth and nitrogen (N) accumulation in Populus deltoides W. Bartram ex Marshall plants infected with rust (Melampsora medusae Thümen.) and to determine how internal N stores are affected by the disease, in plants growing under two N availabilities in the soil; and (ii) to evaluate the impact of rust in the early sprout in the following growing season and the cumulative effect of the disease after repeated infections. Two clones with different susceptibility to rust were analyzed. At leaf level, rust reduced gas exchange capacity, water conductance in liquid phase and photosynthetic rate in both clones. At plant level, rust reduced plant growth, accelerated leaf senescence and abscission occurred with a higher concentration of leaf N. Even though N concentration in stems and roots were not significantly reduced by rust, total N accumulation in perennial tissues was reduced in infected plants. The vigor of the early sprout of plants infected by rust in the previous season was lower than that of non-infected plants. Therefore, rust affects plant growth by reducing the photosynthetic capacity and leaf area duration, and by decreasing internal nutrient recycling. As nutrient reserves in perennial tissues are lower, rust infection reduces not only the growth of the current season, but also has a cumulative effect on the following years. The reduction of growth was similar in both clones. High availability of N in the soil had no effect on leaf physiology but increased plant growth, delayed leaf senescence and abscission, and increased total N accumulation. If fertilization increases plant growth (stem and root dry mass) it can mitigate the negative effect of the pathogen in the reduction of nutrient storages and future growth.EEA Delta del ParanáFil: Gortari, Fermín. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Fisiología Vegetal; ArgentinaFil: Gortari, Fermín. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Instituto de Fisiología Vegetal; ArgentinaFil: Guiamet, Juan José. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Fisiología Vegetal; ArgentinaFil: Guiamet, Juan José. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Instituto de Fisiología Vegetal; ArgentinaFil: Cortizo, Silvia Cora. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Delta del Paraná; ArgentinaFil: Graciano, Corina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Fisiología Vegetal; ArgentinaFil: Graciano, Corina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Instituto de Fisiología Vegetal; Argentina.Fil: Graciano, Corina. Universidad Nacional de La Plata. Facultad de Ciencias Agrarias y Forestales; Argentin

Chloroplast protein degradation in senescing leaves: Proteases and lytic compartments

Leaf senescence is characterized by massive degradation of chloroplast proteins, yet the protease(s) involved is(are) not completely known. Increased expression and/or activities of serine, cysteine, aspartic, and metalloproteases were detected in senescing leaves, but these studies have not provided information on the identities of the proteases responsible for chloroplast protein breakdown. Silencing some senescence-associated proteases has delayed progression of senescence symptoms, yet it is still unclear if these proteases are directly involved in chloroplast protein breakdown. At least four cellular pathways involved in the traffic of chloroplast proteins for degradation outside the chloroplast have been described (i.e., “Rubisco-containing bodies,” “senescence-associated vacuoles,” “ATI1-plastid associated bodies,” and “CV-containing vesicles”), which differ in their dependence on the autophagic machinery, and the identity of the proteins transported and/or degraded. Finding out the proteases involved in, for example, the degradation of Rubisco, may require piling up mutations in several senescence-associated proteases. Alternatively, targeting a proteinaceous protein inhibitor to chloroplasts may allow the inhibitor to reach “Rubisco-containing bodies,” “senescence-associated vacuoles,” “ATI1-plastid associated bodies,” and “CV-containing vesicles” in essentially the way as chloroplast-targeted fluorescent proteins re-localize to these vesicular structures. This might help to reduce proteolytic activity, thereby reducing or slowing down plastid protein degradation during senescence.Fil: Buet, Agustina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Fisiología Vegetal. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Instituto de Fisiología Vegetal; ArgentinaFil: Costa, M.lorenza. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Fisiología Vegetal. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Instituto de Fisiología Vegetal; ArgentinaFil: Martinez, Dana Ethel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Fisiología Vegetal. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Instituto de Fisiología Vegetal; ArgentinaFil: Guiamet, Juan José. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Fisiología Vegetal. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Instituto de Fisiología Vegetal; Argentin

Effet de l’irradiance et de l’eau foliaire sur la mesure de la chlorophylle avec le SPAD 502

The SPAD 502 Chlorophyll Meter can estimate leaf chlorophyll content as a surrogate measure of the nitrogen (N) status of plants, and therefore, it can be used to assess the N requirements of crops. In this work, we show that irradiance, leaf water status and time of measurement (i.e., morning vs. afternoon), may interfere with the SPAD 502 measurements. SPAD values increased by 2-3 units as relative leaf water content decreased from 94 to 87.5% 57492768n wheat leaves. A change in irradiance (from 1100 to 600-650 mmol m⁻² s⁻¹) caused an increase of about 2 SPAD units in potted maize plants. Throughout the day, SPAD values varied by up to 4 units in well-watered plants of maize growing under field conditions. The slope of the response of the SPAD meter to chlorophyll content was steeper in the morning than in the afternoon. Since the range of SPAD values that may separate N deficiency from N surplus in a crop are often relatively narrow, time of measurement, irradiance and plant water status must be taken into account to precisely monitor crop N needs with the SPAD 502.La mesure de la quantité de chlorophylle permet d’estimer la quantité d’azote des plantes, et donc la quantité d’azote à apporter aux cultures. Ici, nous montrons que l’irradiance, l’état hydrique des feuilles ainsi que le moment de la mesure (matin, après-midi) interfèrent avec la mesure de la quantité de chlorophylle.Instituto de Fisiología Vegeta