Phosphate acquisition and metabolism in plants.

Plants need at least 13 different nutrients to maintain optimal growth. Nitrogen and phosphorus, from the Greek 'phôs' (meaning 'light') and 'phoros' (meaning 'bearer'), are the main nutrients limiting plant growth in both agricultural and natural ecosystems. Agriculture has relied heavily since the mid 1950s on the use of synthetic ammonium- and phosphorus-based fertilizers to increase crop productivity. While industrial synthesis of ammonium relies on the chemical conversion of atmospheric nitrogen, phosphorus is mined from finite reserves concentrated in a few countries. Considering our current dependence on phosphorus fertilizers for food production and the geopolitical aspects associated with current resources, it will be important to develop technologies enabling the maintenance of high crop yield with reduced fertilizer input. This will require an in-depth knowledge on the various pathways that enable plants to acquire phosphorus from the soil and maximize its economical use for growth and reproduction. In this primer, we give an overview of the factors limiting phosphorus acquisition by plants and highlight various pathways and strategies plants have evolved at the level of development, metabolism and signal transduction to adapt to phosphorus deficiency

A nuclear factor Y interacting protein of the GRAS family is required for nodule organogenesis, infection thread progression, and lateral root growth

A C subunit of the heterotrimeric nuclear factor Y (NF-YC1) was shown to play a key role in nodule organogenesis and bacterial infection during the nitrogen fixing symbiosis established between common bean (Phaseolus vulgaris) and Rhizobium etli. To identify other proteins involved in this process, we used the yeast (Saccharomyces cerevisiae) two-hybrid system to screen for NFYC1- interacting proteins. One of the positive clones encodes a member of the Phytochrome A Signal Transduction1 subfamily of GRAS (for Gibberellic Acid-Insensitive (GAI), Repressor of GAI, and Scarecrow) transcription factors. The protein, named Scarecrow-like13 Involved in Nodulation (SIN1), localizes both to the nucleus and the cytoplasm, but in transgenic Nicotiana benthamiana cells, bimolecular fluorescence complementation suggested that the interaction with NF-YC1 takes place predominantly in the nucleus. SIN1 is expressed in aerial and root tissues, with higher levels in roots and nodules. Posttranscriptional gene silencing of SIN1 using RNA interference (RNAi) showed that the product of this gene is involved in lateral root elongation. However, root cell organization, density of lateral roots, and the length of root hairs were not affected by SIN1 RNAi. In addition, the expression of the RNAi of SIN1 led to a marked reduction in the number and size of nodules formed upon inoculation with R. etli and affected the progression of infection threads toward the nodule primordia. Expression of NF-YA1 and the G2/M transition cell cycle genes CYCLIN B and Cell Division Cycle2 was reduced in SIN1 RNAi roots. These data suggest that SIN1 plays a role in lateral root elongation and the establishment of root symbiosis in common bean.Facultad de Ciencias Exacta

Effects of Maleic Hydrazide on yield, dry matter content and sprouting in ware potatoes (Solanum tuberosum L. cv. Spunta)

Dada la ausencia de información sobre el uso de Hidrazida Maleica (HM) en la Argentina, el objetivo de este trabajo fue evaluar los efectos del momento (48 y 34 días antes de la entrega, HM1 y HM2 respectivamente) y dosis de aplicación (9 y 12 l.ha-1) de HM [sal potásica de 6-hidroxi-3 (2H)-piridazinona al 36%, Vendaval HM 36 potásico, Síntesis Química, Argentina] sobre el rendimiento, el contenido de materia seca, la gravedad específica, la brotación y las mermas de peso en tubérculos de papa destinados al consumo fresco. Las experiencias se llevaron a cabo en 1995 y 1996 en Villa Dolores, Córdoba (32° S 65° W) en lotes comerciales del cv. Spunta . De los doce tratamientos realizados con HM sólo en uno de ellos se registró una disminución significativa en el rendimiento, en tanto que en el resto no hubo diferencias con el testigo o bien se produjeron incrementos en el rendimiento. El inicio de la brotación en condiciones controladas y en el campo fue significativamente retrasado por las aplicaciones de HM, al igual que el ritmo de crecimiento de los brotes. Luego de la cosecha y durante el almacenamiento, ya sea en pilas campo o en galpón, las mermas de peso totales y por brotación fueron significativamente mayores en los testigos que en los tratamientos con HM. La gravedad específica y el contenido de materia seca de los tubérculos no fueron modificados por las aplicaciones en diferentes dosis y momentos. Se concluye que a las dosis y momentos utilizados, la aplicación de HM permite extender el período de comercialización de los tubérculos sin que se produzcan disminuciones de rendimiento como consecuencia de su aplicación.As the available information on Maleic Hydrazide (MH) in Argentina is scarce, the objective of this study was to evaluate the influence of time (HM1 and HM2) and rates (9 and 12 l.ha-1) of foliar applications of MH [potassium salt of 6-hydroxi-3 (2H)-piridazinone 36%, Vendaval MH 36 potassium, Síntesis Química, Argentina], on yield, sprouting, weigth losses and potato tuber quality for fresh consumption. The experiments were carried out during 1995 and 1996 at Villa Dolores, Córdoba (32º S 65º W) in commercial fields of cv. Spunta. In only one of twelve cases HM application reduced tuber yield while in other cases yield was improved or did not differ from the control. Sprouting time under controlled and field conditions was significantly delayed due to HM applications and the same was true for sprout growth. During storage, either in heaps in the field or in a barn, tuber weight losses were significantly higher in non-treated tubers than in the HM-treated ones. Tuber specific gravity and dry matter content were not modified by HM treatments, besides their values were similar to average values obtained for the same cultivar during several years. It is concluded that HM applied at the doses and time used in this work effectively inhibited sprout growth and reduced weight losses without affecting yield and dry matter content of the tubers.Facultad de Ciencias Agrarias y Forestale

Effects of Maleic Hydrazide on yield, dry matter content and sprouting in ware potatoes (Solanum tuberosum L. cv. Spunta)

Dada la ausencia de información sobre el uso de Hidrazida Maleica (HM) en la Argentina, el objetivo de este trabajo fue evaluar los efectos del momento (48 y 34 días antes de la entrega, HM1 y HM2 respectivamente) y dosis de aplicación (9 y 12 l.ha-1) de HM [sal potásica de 6-hidroxi-3 (2H)-piridazinona al 36%, Vendaval HM 36 potásico, Síntesis Química, Argentina] sobre el rendimiento, el contenido de materia seca, la gravedad específica, la brotación y las mermas de peso en tubérculos de papa destinados al consumo fresco. Las experiencias se llevaron a cabo en 1995 y 1996 en Villa Dolores, Córdoba (32° S 65° W) en lotes comerciales del cv. Spunta . De los doce tratamientos realizados con HM sólo en uno de ellos se registró una disminución significativa en el rendimiento, en tanto que en el resto no hubo diferencias con el testigo o bien se produjeron incrementos en el rendimiento. El inicio de la brotación en condiciones controladas y en el campo fue significativamente retrasado por las aplicaciones de HM, al igual que el ritmo de crecimiento de los brotes. Luego de la cosecha y durante el almacenamiento, ya sea en pilas campo o en galpón, las mermas de peso totales y por brotación fueron significativamente mayores en los testigos que en los tratamientos con HM. La gravedad específica y el contenido de materia seca de los tubérculos no fueron modificados por las aplicaciones en diferentes dosis y momentos. Se concluye que a las dosis y momentos utilizados, la aplicación de HM permite extender el período de comercialización de los tubérculos sin que se produzcan disminuciones de rendimiento como consecuencia de su aplicación.As the available information on Maleic Hydrazide (MH) in Argentina is scarce, the objective of this study was to evaluate the influence of time (HM1 and HM2) and rates (9 and 12 l.ha-1) of foliar applications of MH [potassium salt of 6-hydroxi-3 (2H)-piridazinone 36%, Vendaval MH 36 potassium, Síntesis Química, Argentina], on yield, sprouting, weigth losses and potato tuber quality for fresh consumption. The experiments were carried out during 1995 and 1996 at Villa Dolores, Córdoba (32º S 65º W) in commercial fields of cv. Spunta. In only one of twelve cases HM application reduced tuber yield while in other cases yield was improved or did not differ from the control. Sprouting time under controlled and field conditions was significantly delayed due to HM applications and the same was true for sprout growth. During storage, either in heaps in the field or in a barn, tuber weight losses were significantly higher in non-treated tubers than in the HM-treated ones. Tuber specific gravity and dry matter content were not modified by HM treatments, besides their values were similar to average values obtained for the same cultivar during several years. It is concluded that HM applied at the doses and time used in this work effectively inhibited sprout growth and reduced weight losses without affecting yield and dry matter content of the tubers.Facultad de Ciencias Agrarias y Forestale

A nuclear factor Y interacting protein of the GRAS family is required for nodule organogenesis, infection thread progression, and lateral root growth

A C subunit of the heterotrimeric nuclear factor Y (NF-YC1) was shown to play a key role in nodule organogenesis and bacterial infection during the nitrogen fixing symbiosis established between common bean (Phaseolus vulgaris) and Rhizobium etli. To identify other proteins involved in this process, we used the yeast (Saccharomyces cerevisiae) two-hybrid system to screen for NFYC1- interacting proteins. One of the positive clones encodes a member of the Phytochrome A Signal Transduction1 subfamily of GRAS (for Gibberellic Acid-Insensitive (GAI), Repressor of GAI, and Scarecrow) transcription factors. The protein, named Scarecrow-like13 Involved in Nodulation (SIN1), localizes both to the nucleus and the cytoplasm, but in transgenic Nicotiana benthamiana cells, bimolecular fluorescence complementation suggested that the interaction with NF-YC1 takes place predominantly in the nucleus. SIN1 is expressed in aerial and root tissues, with higher levels in roots and nodules. Posttranscriptional gene silencing of SIN1 using RNA interference (RNAi) showed that the product of this gene is involved in lateral root elongation. However, root cell organization, density of lateral roots, and the length of root hairs were not affected by SIN1 RNAi. In addition, the expression of the RNAi of SIN1 led to a marked reduction in the number and size of nodules formed upon inoculation with R. etli and affected the progression of infection threads toward the nodule primordia. Expression of NF-YA1 and the G2/M transition cell cycle genes CYCLIN B and Cell Division Cycle2 was reduced in SIN1 RNAi roots. These data suggest that SIN1 plays a role in lateral root elongation and the establishment of root symbiosis in common bean.Facultad de Ciencias Exacta

A statistical comparison of solar wind sources of moderate and intense geomagnetic storms at solar minimum and maximum

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95223/1/jgra17913.pd

Edaphic and follar phosphoric fertilization, during autumn and spring sowings of Lotus tenuis in a Salado river basin soil

El objetivo del trabajo fue evaluar la respuesta de Lotus tenuis a la fertilización con fósforo, aplicado por vía foliar y radical, durante la implantación de la especie en un suelo de la “Pampa Deprimida”, en dos períodos de siembra: otoño y primavera. Se cultivaron plantas en macetas de 4 litros de capacidad en un suelo Hapiudol thapto árgico, del Partido de S. M. del Monte y se probó fa fertilización con fósforo, en los siguientes tratamientos: A- 100 kg.ha-1 (como P2 O5) aplicados en el suelo, en el momento de la siembra; B1- 6 kg.ha-1 asperjado sobre el follaje al estado de 3 hojas expandidas; B2- 6 kg.ha-1 asperjados al estado de 6 hojas expandidas y 2 ramas incipientes y C- Testigo sin fertilizar. Se evaluó la respuesta a estos tratamientos en siembras de otoño y primavera, determinándose: número de ramas y hojas, área foliar total, materia seca de la parte aérea y raíz y número de nódulos, en dos cosechas realizadas a los 30 y 75 días de la aplicación foliar B2. Se observó una respuesta significativa en la producción de biomasa en el tratamiento A, especialmente en la parte aérea, quintuplicando los valores del testigo en la siembra de otoño y triplicándolos en la siembra de primavera. La partición de la biomasa fue modificada por la fertilización en el suelo, con un mayor crecimiento de la parte aérea en relación a la subterránea, en mayor medida para la siembra de otoño. La fertilización foliar, en el tratamiento Bv también aumentó la producción de biomasa, con respecto al testigo, 60 % en otoño y 37 % en primavera. El tratamiento B2 fue significativamente superior al testigo en un 46 % sólo en otoño. La modulación también aumentó significativamente en todos los tratamientos de fertilización; el número de nódulos se incrementó proporcionalmente al aumento de biomasa. Como consecuencia del incremento en biomasa obtenida por la fertilización con fósforo, edáfica y foliar, se favorecería un más rápido establecimiento del cultivo y, eventualmente, un aprovechamiento forrajero más temprano, especialmente en siembras de otoño.The aim of this research was to evaluate the response of Lotus tenuis to fertilization with phosphorus. either applied to the soil or to the foliage. The experiment was carried out in a Hapludol thapto argic soil of the Salado River Basin area, in two sowing dates: autumm and spring. Plants were cultivated in pots with soil of the area and phosphortc fertilízation was tested as follows: A) to the soil at sowing at a dose of 100 kg.ha-1 (as P2Os), B1) foliarty at 6 kg.ha-1 at 3-leaves stage, B2) foliariy at 6 kg.ha-1 at 6-leaves stage and 2 incipient branches and C) control. Two harvests per growing season (at 30 and 75 days after B2 treatment) were performed to evalúate number of branches and leaves, total foliar area, dry matter of the aerial part and the roots and number of nodules. Biomass production on treatment A was significantly increased mainly in the aerial part, exceeding five and three times the control in regard to the autumm and spring sowing, respectively. The aerial dry matter was increased due to soil P-fertilization, mainly in autumm. Foliar fertilization (B,) also showed an increase in biomass production in 60 % and 37 % during autumm and spring respectively. B2 treatment only increased biomass production by 46 % in autumm. Root nodules were also augmentad by all fertilizers treatments and the nodule number was enhanced in relation to total biomass. It’s concluded that P-fertilization either applied to soil or to foliage due to biomass increase , perhaps advanee the production early in the season and improve forage use, mainly in autumm.Universidad Nacional de La Plata (UNLP) - Facultad de Ciencias Agrarias y Forestale