M. Ángeles Botella

KINETICS OF NO3- AND NH4+ UPTAKE BY WHEAT SEEDLINGS : EFFECT OF SALINITY AND NITROGEN SOURCE

Summary The kinetic parameters K m and V max for the uptake of NO 3 − and NH 4 + were determined in wheat plants grown in nutrient

Nitrate Reductase Activity in Wheat Seedlings as Affected by NO3-/NH4+ Ratio and Salinity

Summary Nitrate reductase is considered to be a limiting factor for growth, development and protein production in plants. This enzyme is influenced by external conditions. The purpose of this study was to investigate the effect of different NO 3 -/NH 4 + ratios and salinity on NRA (nitrate reductase activity) in shoots and roots of wheat ( Triticum aestivum L. cv. Betres) seedlings. Plants were grown in a growth chamber under controlled conditions. Nutrient solution contained 4 mM N, applied as NO 3 - and NH 4 + in different ratios, and saline treatments consisted in two levels of NaCl: 1 mM and 60 mM. Wheat seedlings had most of their NRA in shoots. When NH 4 + was present in the nutrient solution NRA was almost completely inhibited in roots and decreased in shoots. Inhibition of NRA by NH4+ seems to be a direct effect on synthesis and activity of NR rather than through inhibition of NO 3 - uptake and thus by lack of substrate. Salinity significantly decreased NRA in shoots, this effect being influenced by NO 3 - in the and by NO 3 -/Cl - ratio in shoots. The effect on RNA may be due to the alteration of NO 3 - uptake, to an excessive CI - shoot content which may affect NO 3 - transport from vacuoles to cytoplasm and to the alteration of NO 3 - flux from root to shoot.

Nutritional and antioxidant properties of wild edible plants and their use as potential ingredients in the modern diet

Abstract Thirteen species of wild edible plants belonging to 11 botanical families consumed in the traditional Mediterranean diet were evaluated. Sanguisorba minor, Quercus ballota and Sedum sediforme showed the highest hydrophilic total antioxidant activity (H-TAA) and total phenols. Asparagus acutifolius, Allium ampeloprasum, Foeniculum vulgare and Malva sylvestris presented high levels of potassium, Malva and Asparagus are interesting due to their zinc content, and Urtica urens contains a high content of calcium. Sensory analysis indicated that fruits from Q. ballota could be considered very sweet and plants of Crithmum maritimum and Oxalis pes-caprae are very acidic. Moreover, testers highlighted the salty taste of C. maritimum. Mesembryanthemum nodiflorum and Mesembryanthemum cristalinum, the spicy taste of A. ampeloprasum, and the aroma of F. vulgare. Our results indicate that increased consumption of the investigated plant species could provide health benefits. Moreover, due to their sensorial properties, they could be used as new ingredients to improve the diversity in modern diet and highly creative cuisine.

High Ca2+ reverts the repression of high-affinity K+ uptake produced by Na+ in Solanum lycopersycum L. (var. microtom) plants

Potassium (K(+)) is an essential nutrient for plants which is acquired by plant roots through the operation of specific transport systems. Abiotic stress conditions such as salinity impair K(+) nutrition because, in addition to other effects, high salt concentrations in the solution bathing the roots inhibit K(+) uptake systems. This detrimental effect of salinity is exacerbated when external K(+) is very low and the only system capable of mediating K(+) uptake is one with high-affinity for K(+), as that mediated by transporters of the HAK5 type. Increasing external Ca(2+) has been shown to improve K(+) nutrition under salinity and, although the specific mechanisms for this beneficial effect are largely unknown, they are beginning to be understood. The genes encoding the HAK5 transporters are induced by K(+) starvation and repressed by long-term exposure to high Na(+). This occurs in parallel with the hyperpolarization and depolarization of root cell membrane potential. In the present study it is shown in tomato plants that the presence of high Ca(2+) during the K(+) starvation period that leads to LeHAK5 induction, counteracts the repression exerted by high Na(+). High Ca(2+) reduces the Na(+)-induced plasma membrane depolarization of root cells, resorting one of the putative first steps in the low-K(+) signal cascade. This allows proper LeHAK5 expression and functional high-affinity K(+) uptake at the roots. Thus, the maintenance of HAK5-mediated K(+) nutrition under salinity by high Ca(2+) can be regarded as a specific beneficial effect of Ca(2+) contributing to salt tolerance in plants.

NO3−, PO43− and SO42− deprivation reduced LKT1-mediated low-affinity K+ uptake and SKOR-mediated K+ translocation in tomato and Arabidopsis plants

Regulation of essential macronutrients acquisition by plants in response to their availability is a key process for plant adaptation to changing environments. Here we show in tomato and Arabidopsis plants that when they are subjected to NO3- , PO43- and SO42- deprivation, low-affinity K+ uptake and K+ translocation to the shoot are reduced. In parallel, these nutritional deficiencies produce reductions in the messenger levels of the genes encoding the main systems for low-affinity K+ uptake and K+ translocation, i.e. AKT1 and SKOR in Arabidopsis and LKT1 and the tomato homolog of SKOR, SlSKOR in tomato, respectively. The results suggest that the shortage of one nutrient produces a general downregulation of the acquisition of other nutrients. In the case of K+ nutrient, one of the mechanisms for such a response resides in the transcriptional repression of the genes encoding the systems for K+ uptake and translocation.

Potassium fertilization enhances pepper fruit quality

ABSTRACT The effect of potassium (K+) concentration on the nutritional quality and yield of pepper fruits was evaluated. Pepper plants were grown in a controlled-environment greenhouse under hydroponic conditions with different nutrient solutions obtained by modifying the Hoagland solution to achieve different K+ concentrations. Potassium nutrition affected fruit yield parameters more than vegetative biomass in pepper plants. The maximum fruit yield was obtained with 7 mM K+ in the nutrient solution. However, it is possible to improve the bioactive compounds of pepper fruits with a higher application of K+ without reducing yield. The increase of K+ in the nutrient solution improved pepper fruit quality by increasing fruit firmness, TSS content, soluble sugars and ascorbic acid concentration. Therefore, the fruit quality improvements obtained with adequate K+ nutrition resulted in nutritionally enriched fruits, which, at little or no extra cost, benefits the consumer.

Cultural Importance of Wild or Traditionally Collected Plants in the Sierra de Grazalema (Southern Spain)

ABSTRACTThe aim of this work is to evaluate the knowledge about, and diversity and cultural significance of, wild or traditionally collected plants used in the Sierra de Grazalema, located in Southeastern Spain. Nine hundred and ninety-three use reports for 98 popular names, corresponding to 124 species, were recorded. The ethnobotanical information was obtained through semi-structured interviews with open-ended questions. Informants had high empirical knowledge of wild plants and lived and/or worked in the area. The human food uses showed the highest use reports with 40% of the total, followed by that of technological uses with 30%. Mentha pulegium (pennyroyal) is the most culturally significant plant in the area according to the cultural importance index (1.50). The second plant in the ranking (1.20) is Olea europaea var. sylvestris (wild olive). Inflorescences from Helichrysum italicum and Helichrysum stoechas have medicinal uses (0.94). The fourth plant in the cultural importance index ranking is Scolymus hispanicus (0.97). Finally, amongst the most popular plants in the Sierra de Grazalema is Phlomis purpurea (0.97). Our results indicate that in the Sierra de Grazalema, some wild or traditionally collected plants are deeply rooted in popular culture. The cultural importance index presented in this work could be a useful tool to evaluate the possibilities of sustainable exploitation of these resources.RESUMENEl objetivo de este trabajo es evaluar el conocimiento, la diversidad y la significancia cultural de los usos de las plantas silvestres o tradicionalmente recolectadas en la Sierra de Grazalema, ubicada en el sureste de España. Se obtuvieron 993 registros para 98 nombres populares, correspondientes a 124 especies. La información etnobotánica se obtuvo a través de entrevistas semi-estructuradas con preguntas abiertas. Los informantes tenían un alto conocimiento empírico de las plantas silvestres y vivían y/o trabajaban en la zona. Los usos para alimentación humana fueron los más populares, con el 40% de los registros, seguido por el de usos tecnológicos con el 30%. Mentha pulegium (poleo) es la planta más importante de la zona según el índice de importancia cultural (1.50). La segunda planta en el ranking (1.20) es Olea europaea var. sylvestris (acebuche). Las inflorescencias de Helichrysum italicum y Helichrysum stoechas son conocidas por sus usos medicinales (0.94). La cuarta planta en el ranking del índice de importancia cultural es Scolymus hispanicus (0.97). Finalmente, entre las plantas más populares en la Sierra de Grazalema se encuentra Phlomis purpurea (0.97). Nuestros resultados indican que en la Sierra de Grazalema, algunas plantas silvestres o tradicionalmente recolectadas están profundamente arraigadas en la cultura popular. El índice de importancia cultural presentado en este trabajo podría ser una herramienta útil para evaluar las posibilidades de explotación sostenible de estos recursos.

Effect of rootstock on salt tolerance of loquat: growth and mineral composition.

The salinity tolerance of loquat grafted onto anger or onto loquat was studied. The plants were irrigated using solutions containing 5, 25, 35, 50, or 70 mM sodium chloride (NaCl) for five months. Different parameters of vegetative growth were studied, all of them showing that plants grafted onto loquat are much less salinity-tolerant than those grafted onto anger. Thus, the concentration of NaCl that produced a growth reduction of 50% (C50) for the growth parameters of the shoot was around 35 mM for loquat plants grafted onto loquat. With the NaCl levels employed, loquat-anger plants did not reach the C50. Lower chloride (Cl−) and sodium (Na+) uptake, higher potassium (K+)-Na+ selectivity and a lower reduction in the leaf magnesium (Mg2+) concentration for the loquat-anger combination can explain the higher salinity tolerance compared to loquat-loquat.