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1.
Physiol Plant ; 157(2): 234-54, 2016 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-26806194

RESUMEN

Despite the development of various methods, the rapid estimation of mesophyll conductance (gm ) for a large number of samples is still a daunting challenge. Although the accurate estimation of gm is critical to partition photosynthetic limitations by stomatal (Ls ) and mesophyll (Lm ) conductance and by photo-biochemical (Lb ) processes, the impact of various gm estimation methods on this is ambiguous. As phosphorus (P) starvation and elevated CO2 (eCO2 ) strongly affect photosynthetic processes, their combined effect on the proportional changes in these limitations are not well understood. To investigate this, while also evaluating distinct recent methods of gm estimation sharing few common theories and assumptions, soybean was grown under a range of P nutrition at ambient and eCO2 . Methods significantly affected gm and carboxylation efficiency (VCmax ) but not other photosynthetic parameters. In all the methods, all photosynthetic parameters responded similarly to treatments. However, the percentage difference between VCmax assuming finite and infinite gm was highly inconsistent among methods. The primary mechanism responsible for P limitation to soybean photosynthesis was not CO2 diffusion limitations but Lb comprised of reduced chlorophyll, photochemistry and biochemical processes. The eCO2 decreased Lb but increased Lm without affecting Ls across leaf P concentration. Although each method explored advances of our understanding about gm variability, they all require assumptions of varying degrees, which lead to the discrepancy in the gm values. Among the methods, the oxygen sensitivity-based gm estimation appeared to be suitable for the quick assessment of a large number of samples or genotypes. Digital tools are provided for the easy estimation of gm for some methods.


Asunto(s)
Glycine max/fisiología , Células del Mesófilo/fisiología , Fósforo/deficiencia , Fotosíntesis , Transpiración de Plantas/fisiología , Dióxido de Carbono/metabolismo , Clorofila/metabolismo , Difusión , Luz , Células del Mesófilo/efectos de la radiación , Hojas de la Planta/fisiología , Estomas de Plantas/fisiología , Transpiración de Plantas/efectos de la radiación , Glycine max/efectos de la radiación
2.
Am J Bot ; 99(10): 1702-14, 2012 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-22984095

RESUMEN

PREMISE OF THE STUDY: Consequences of global climate change are detectable in the historically nitrogen- and phosphorus-limited Arctic tundra landscape and have implications for the terrestrial carbon cycle. Warmer temperatures and elevated soil nutrient availability associated with increased microbial activity may influence rates of photosynthesis and respiration. • METHODS: This study examined leaf-level gas exchange, cellular ultrastructure, and related leaf traits in two dominant tundra species, Betula nana, a woody shrub, and Eriophorum vaginatum, a tussock sedge, under a 3-yr-old treatment gradient of nitrogen (N) and phosphorus (P) fertilization in the North Slope of Alaska. • KEY RESULTS: Respiration increased with N and P addition-the highest rates corresponding to the highest concentrations of leaf N in both species. The inhibition of respiration by light ("Kok effect") significantly reduced respiration rates in both species (P < 0.001), ranged from 12-63% (mean 34%), and generally decreased with fertilization for both species. However, in both species, observed rates of photosynthesis did not increase, and photosynthetic nitrogen use efficiency generally decreased under increasing fertilization. Chloroplast and mitochondrial size and density were highly sensitive to N and P fertilization (P < 0.001), though species interactions indicated divergent cellular organizational strategies. • CONCLUSIONS: Results from this study demonstrate a species-specific decoupling of respiration and photosynthesis under N and P fertilization, implying an alteration of the carbon balance of the tundra ecosystem under future conditions.


Asunto(s)
Betula/metabolismo , Ciclo del Carbono , Cyperaceae/metabolismo , Nitrógeno/metabolismo , Fósforo/metabolismo , Hojas de la Planta/citología , Hojas de la Planta/metabolismo , Análisis de Varianza , Regiones Árticas , Betula/citología , Betula/crecimiento & desarrollo , Betula/ultraestructura , Biomasa , Ciclo del Carbono/efectos de la radiación , Dióxido de Carbono/metabolismo , Respiración de la Célula/efectos de la radiación , Cloroplastos/metabolismo , Cloroplastos/efectos de la radiación , Cloroplastos/ultraestructura , Cyperaceae/citología , Cyperaceae/crecimiento & desarrollo , Cyperaceae/ultraestructura , Fertilización/efectos de la radiación , Luz , Células del Mesófilo/citología , Células del Mesófilo/efectos de la radiación , Células del Mesófilo/ultraestructura , Mitocondrias/metabolismo , Mitocondrias/efectos de la radiación , Mitocondrias/ultraestructura , Consumo de Oxígeno/efectos de la radiación , Fotosíntesis/efectos de la radiación , Hojas de la Planta/anatomía & histología , Hojas de la Planta/efectos de la radiación , Estaciones del Año , Temperatura
3.
Physiol Plant ; 146(3): 308-20, 2012 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-22471584

RESUMEN

The continuous atmospheric and environmental deterioration is likely to increase, among others, the influx of ultraviolet B (UV-B) radiation. The plants have photoprotective responses, which are complex mechanisms involving different physiological responses, to avoid the damages caused by this radiation that may lead to plant death. We have studied the adaptive responses to UV-B in Pinus radiata, given the importance of this species in conifer forests and reforestation programs. We analyzed the photosynthetic activity, pigments content, and gene expression of candidate genes related to photosynthesis, stress and gene regulation in needles exposed to UV-B during a 96 h time course. The results reveal a clear increase of pigments under UV-B stress while photosynthetic activity decreased. The expression levels of the studied genes drastically changed after UV-B exposure, were stress related genes were upregulated while photosynthesis (RBCA and RBCS) and epigenetic regulation were downregulated (MSI1, CSDP2, SHM4). The novel gene PrELIP1, fully sequenced for this work, was upregulated and expressed mainly in the palisade parenchyma of needles. This gene has conserved domains related to the dissipation of the UV-B radiation that give to this protein a key role during photoprotection response of the needles in Pinus radiata.


Asunto(s)
Epigénesis Genética/fisiología , Regulación de la Expresión Génica de las Plantas/fisiología , Fotosíntesis/fisiología , Pinus/fisiología , Proteínas de Plantas/genética , Estrés Fisiológico/fisiología , Antocianinas/metabolismo , Carotenoides/metabolismo , Clorofila/metabolismo , ADN Complementario/genética , Regulación hacia Abajo , Epigénesis Genética/genética , Hibridación Fluorescente in Situ , Células del Mesófilo/citología , Células del Mesófilo/fisiología , Células del Mesófilo/efectos de la radiación , Modelos Moleculares , Filogenia , Pinus/citología , Pinus/genética , Pinus/efectos de la radiación , Hojas de la Planta/citología , Hojas de la Planta/genética , Hojas de la Planta/fisiología , Hojas de la Planta/efectos de la radiación , Proteínas de Plantas/metabolismo , Estructura Terciaria de Proteína , ARN de Planta/genética , Árboles , Rayos Ultravioleta , Regulación hacia Arriba
4.
J Exp Bot ; 62(8): 2841-54, 2011 May.
Artículo en Inglés | MEDLINE | ID: mdl-21357771

RESUMEN

Class III peroxidases (Prxs) are plant enzymes capable of using H(2)O(2) to oxidize a range of plant secondary metabolites, notably phenolic compounds. These enzymes are localized in the cell wall or in the vacuole, which is a target for secondary metabolite accumulation, but very little is known about the function of vacuolar Prxs. Here, the physiological role of the main leaf vacuolar Prx of the medicinal plant Catharanthus roseus, CrPrx1, was further investigated namely by studying its capacity to oxidize co-localized phenolic substrates at the expense of H(2)O(2). LC-PAD-MS analysis of the phenols from isolated leaf vacuoles detected the presence of three caffeoylquinic acids and four flavonoids in this organelle. These phenols or similar compounds were shown to be good CrPrx1 substrates, and the CrPrx1-mediated oxidation of 5-O-caffeoylquinic acid was shown to form a co-operative regenerating cycle with ascorbic acid. Interestingly, more than 90% of total leaf Prx activity was localized in the vacuoles, associated to discrete spots of the tonoplast. Prx activity inside the vacuoles was estimated to be 1809 nkat ml(-1), which, together with the determined concentrations for the putative vacuolar phenolic substrates, indicate a very high H(2)O(2) scavenging capacity, up to 9 mM s(-1). Accordingly, high light conditions, known to increase H(2)O(2) production, induced both phenols and Prx levels. Therefore, it is proposed that the vacuolar couple Prx/secondary metabolites represent an important sink/buffer of H(2)O(2) in green plant cells.


Asunto(s)
Catharanthus/enzimología , Peróxido de Hidrógeno/metabolismo , Peroxidasa/metabolismo , Fenoles/metabolismo , Plantas Medicinales/enzimología , Vacuolas/enzimología , Ácido Ascórbico/metabolismo , Catharanthus/efectos de la radiación , Catharanthus/ultraestructura , Isoenzimas/metabolismo , Luz , Espectrometría de Masas , Células del Mesófilo/citología , Células del Mesófilo/enzimología , Células del Mesófilo/efectos de la radiación , Células del Mesófilo/ultraestructura , Oxidación-Reducción/efectos de la radiación , Fenoles/química , Fenoles/aislamiento & purificación , Extractos Vegetales , Hojas de la Planta/enzimología , Hojas de la Planta/efectos de la radiación , Hojas de la Planta/ultraestructura , Plantas Medicinales/efectos de la radiación , Plantas Medicinales/ultraestructura , Protoplastos/metabolismo , Espectrofotometría Ultravioleta , Especificidad por Sustrato/efectos de la radiación , Factores de Tiempo , Vacuolas/efectos de la radiación , Vacuolas/ultraestructura
5.
Photochem Photobiol ; 87(3): 685-9, 2011.
Artículo en Inglés | MEDLINE | ID: mdl-21275997

RESUMEN

Phyllanthus tenellus is widely used for its antiviral, analgesic and hepatoprotective properties. Although the production of several chemical classes of secondary metabolites is influenced by UV radiation, particularly phenolic compounds, we also know that UV radiation can result in anatomical and developmental damage. However, the morphological, anatomical and phytochemical changes in response to UV-A exposure are generally understudied in the Phyllanthaceae. Therefore, we evaluated the effects of UV-A radiation on plant development and leaf anatomy, as well as the production of secondary metabolites and the contents of carotenoids and chlorophylls a and b, in P. tenellus. To accomplish this, in vitro cultures of P. tenellus were maintained for 60 days under white light (WL) and WL plus UV-A radiation. Results showed different phenotypic responses under additional UV-A, such as high phenolic metabolite production, increasing dimensions of abaxial epidermis and thickness of palisade parenchyma. Compared to plants cultured under WL, UV-A radiation caused damage to plant morphogenesis, including a reduced number of branches and shoots, consequently reducing the rate of proliferation. On the other hand, geraniin, ellagic acid and carotenoid contents increased after UV-A exposure, indicating that this light source is an important resource for inducing phenolic compounds.


Asunto(s)
Carotenoides/biosíntesis , Flavonoides/biosíntesis , Phyllanthus/efectos de la radiación , Hojas de la Planta/efectos de la radiación , Brotes de la Planta/efectos de la radiación , Carotenoides/análisis , Clorofila/análisis , Clorofila/biosíntesis , Técnicas de Cultivo , Ácido Elágico/análisis , Ácido Elágico/metabolismo , Flavonoides/análisis , Glucósidos/análisis , Glucósidos/biosíntesis , Taninos Hidrolizables/análisis , Luz , Células del Mesófilo/efectos de la radiación , Phyllanthus/anatomía & histología , Phyllanthus/crecimiento & desarrollo , Phyllanthus/metabolismo , Epidermis de la Planta/efectos de la radiación , Hojas de la Planta/anatomía & histología , Hojas de la Planta/crecimiento & desarrollo , Hojas de la Planta/metabolismo , Brotes de la Planta/anatomía & histología , Brotes de la Planta/crecimiento & desarrollo , Brotes de la Planta/metabolismo
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