Maria Rosaria Panuccio

Effects of salinity on growth, carbohydrate metabolism and nutritive properties of kikuyu grass (Pennisetum clandestinum Hochst)

Abstract The objective of this study was to investigate the effect of salinity on growth, nutritive properties and carbohydrate metabolism of Pennisetum clandestinum Hochst. Salt stress was induced by adding NaCl at different concentrations to the nutrient solution: 0, 50, 100, 150 and 200 mM. After 15 days under such stress, plants were actively growing up to 100 mM NaCl. Salinity affected root length more than leaf length. The invertase activity significantly enhanced in leaves and decreased in roots of kikuyu grass at 150 and 200 mM NaCl. In plants exposed to highest salt conditions, we observed an accumulation of hexoses and a lower activity of glucokinase (GK), phosphoglucoisomerase (GPI) and pyruvate kinase (PK). The glucose-6-phosphate dehydrogenase (G6PDH) decreased increasing salt concentration, showing at 200 mM NaCl the strongest reduction. The phosphoenolpyruvate carboxykinase (PEPCK) activity slightly and progressively increased in a concentration-dependent manner. Exposure of kikuyu grass to 150 and 200 mM NaCl caused an increase of NADP+-specific isocitrate dehydrogenase (IDH) activity in leaves and roots. The nutritive properties of kikuyu decreased in grass treated with 150 mM and even more with 200 mM NaCl. These data indicate that kikuyu is a grass tolerant to salinity up to 100 mM, suggesting its possible utilization in saline land where the survival of other fodder species is markedly reduced.

Auxin-like effect of humic substances extracted from faeces of Allolobophora caliginosa and A. rosea

Abstract Lef explants of Nicotiana plumbaginifolia were compared in cultures supplemented with IAA, inhibitors of IAA (TIBA = 2,3,5-triiodobenzoic acid and PCIB = 4-chlorophenoxy-isobutyric acid) and a humic substance (HEf) obtained from the faeces of yAllolobophora caliginosa and A. rosea . The results show that HEf at a concentration of 1 mg Cl −1 causes root development from leaf explants that appears to be similar to IAA-induced activity, while the control did not develop roots. Furthermore HEf induced longer roots than those grown in IAA with fewer hair roots. In the presence of the IAA inhibitors, the leaf explants were without roots. Humic matter, IAA and IAA-inhibitors stimulated peroxidase activity in N. plumbaginifolia . Also, when the Nicotiana tissues were treated with the humic fraction and IAA there was a minor polymorphism in the esterase isoenzymes. The presence of both TIBA and PCIB restored the esterase profile obtained from control tissues. The induced root-forming activity in leaf explants and the minor polymorphism with respect to the control in the esterase zymograms demonstrate that the humic substance exhibited auxin-like activity. HEf, a low molecular size fraction, was obtained from the faeces of Allolobophora caliginosa (Sav.) and A. rosea (Sav.) by disaggregating the humic material with acetic acid, confirmed the effectiveness of the combination of high acidity and low molecular size in influencing the biological activity of the plant system tested.

The effect of phenols on respiratory enzymes in seed germination

Low molecular weight phenolic compounds were identified in two soilswith different vegetative cover, Fagus sylvatica, L. andPinus laricio, Poiret, spp. calabrica, and were tested atdifferent concentrations on seed germination of Pinuslaricio, and on respiratory and oxidative pentose phosphate pathwayenzymes involved in the first steps of seed germination. The data obtained showthat there are marked differences in the phenolic acid composition of the twoinvestigated soils. All the phenolic compounds bioassayed inhibited seedgermination and those extracted from Pinus laricio soilwere particularly inhibitory. We also found that the non-germination of seedsisstrongly correlated to the inhibition of the activities of enzymes ofglycolysisand the oxidative pentose phosphate pathway.

Effect of saline water on seed germination and early seedling growth of the halophyte quinoa

The introduction of new crops with improved salinity stress tolerance could preserve water quality and protect soil resources from further degradation, providing extra sources of food for salinized areas. In this context, we tested the salinity tolerance of a variety of quinoa. Quinoa, a rich source of minerals, proteins and antioxidants, is considered a major alternative crop to meet food shortages in this century. Our study indicated that salinity tolerance of quinoa is largely conferred by a delicate balance between osmotic adjustment and ion accumulation. Salinity reduced productivity in terms of biomass, but increased the levels of antioxidant compounds, which are important health-protecting factors in food, thus providing economic benefit.

Salt tolerance traits increase the invasive success of Acacia longifolia in Portuguese coastal dunes.

Salt tolerance of two co-occurring legumes in coastal areas of Portugal, a native species--Ulex europaeus, and an invasive species--Acacia longifolia, was evaluated in relation to plant growth, ion content and antioxidant enzyme activities. Plants were submitted to four concentrations of NaCl (0, 50, 100 and 200 mM) for three months, under controlled conditions. The results showed that NaCl affects the growth of both species in different ways. Salt stress significantly reduced the plant height and the dry weight in Acacia longifolia whereas in U. europaeus the effect was not significant. Under salt stress, the root:shoot ratio (W(R):W(S)) and root mass ratio (W(R):W(RS)) increased as a result of increasing salinity in A. longifolia but the same was not observed in U. europaeus. In addition, salt stress caused a significant accumulation of Na+, especially in U. europaeus, and a decrease in K+ content and K+/Na+ ratio. The activities of antioxidant enzymes were higher in A. longifolia compared to U. europaeus. In A. longifolia, catalase (CAT, EC 1.11.1.6) and glutathione reductase (GR, EC 1.6.4.2.) activities increased significantly, while ascorbate peroxidase (APX, EC 1.11.1.11) and peroxidase (POX, EC 1.11.1.7) activities remained unchanged in comparison with the control. In U. europaeus, NaCl concentration significantly reduced APX activity but did not significantly affect CAT, GR and POX activities. Our results suggest that the invasive species copes better with salinity stress in part due to a higher rates of CAT and GR activities and a higher K+/Na+ ratio, which may represent an additional advantage when competing with native species in co-occurring salty habitats.

EFFECT OF HUMIC SUBSTANCES ON NITROGEN UPTAKE AND ASSIMILATION IN TWO SPECIES OF PINUS

The effects of a humic fraction, with a high molecular weight (Hsp) extracted from a soil with a Fagus sylvatica vegetal cover were compared on ammonium (NH+ 4) and nitrate (NO− 3) uptake in two different coniferous species (Pinus pinaster and Pinus laricio). The activity of malate dehydrogenase (MDH; EC 1.1.1.37), glutamate dehydrogenase (GDH; EC 1.4.1.3) and phosphoenolpyruvate carboxylase (PEPC; EC 4.1.1.31) key enzymes involved in nitrogen metabolism were tested. The data obtained indicate that the humic fractions, at all concentrations, increased ammonium uptake by both species, while nitrate uptake was unaffected. In P. laricio seedlings this fraction increased only leaf malate dehydrogenase activity, while in P. pinaster seedlings an increase of glutamate dehydrogenase in leaves, and of phosphoenolpyruvate carboxylase activity in both roots and leaves was observed. These results show that humic substances stimulate only ammonium uptake and differently influence ammonium assimilation in the two species of Pinus. This diverse behavior might be related to the different environmental conditions where these two species live.

Tolerance of kikuyu grass to long term salt stress is associated with induction of antioxidant defences

The response of the antioxidant system to long term (15 d) salt stress (50, 100, 200 mM NaCl) was studied in kikuyu (Pennisetum clandestinum, Hochst.), a perennial grass with a well developed root system (often used as an erosion controlling ground cover) and with high nutritive properties as pasture. The activities of peroxidase, catalase, ascorbate peroxidase, ascorbate-free radical reductase, glutathione reductase and dehydroascorbate reductase enzymes involved in the detoxification from reactive oxygen species were investigated. The growth of kikuyu grass was inhibited at 200 mM NaCl. Salinity affected root length more than leaf length. Lower activities of catalase, ascorbate-free radical reductase, and dehydroascorbate reductase enzymes were observed in stressed plants. The tolerance of kikuyu grass to salt stress (up to 100 mM) appears to be related to up-regulation of ascorbate peroxidase, peroxidase and glutathione reductase enzymes.

Antioxidant Properties and Flavonoid Profile in Leaves of Calabrian Lavandula multifida L., an Autochthon Plant of Mediterranean Southern regions

Lavandula multifida is a rare short‐lived plant characteristic of Mediterranean basin able to survive in hot and arid climatic conditions on poorly evolved limestone soils. In this work, we characterize the enzymatic antioxidant system and phenolic composition, as well as the antioxidant properties of L. multifida fresh leaves. Enzymatic patterns show high level of peroxidases, ascorbate peroxidase, and dehydroascorbate reductase activities, when compared with L. angustifolia. The same trend is evident in total carotenoids, ascorbic acid, and reduced glutathione, and in the total antioxidant capacity assay. Moreover, RP‐DAD‐HPLC analyses of EtOH extract, obtained from fresh leaves, reveal main components, carvacrol, vitexin, and 7‐ or 8‐glucoside derivatives of hypolaetin, scutellarein, luteolin, isoscutellarein, apigenin, and chrysoeriol. The analysis of this autochthon plant depicted a series of strategies adopted by L. multifida to survive in its stressful natural habitat and richness in health‐promoting compounds that can be a resource for the preservation of this variety in dangerous of extinction.

Anaerobic co-digestion of recalcitrant agricultural wastes: Characterizing of biochemical parameters of digestate and its impacts on soil ecosystem

Anaerobic digestion (AD) of organic wastes is a promising alternative to landfilling for reducing Greenhouse Gas Emission (GHG) and it is encouraged by current regulation in Europe. Biogas-AD produced, represents a useful source of green energy, while its by-product (digestate) is a waste, that needs to be safely disposal. The sustainability of anaerobic digestion plants partly depends on the management of their digestion residues. This study has been focused on the environmental and economic benefits of co-digest recalcitrant agricultural wastes such olive wastes and citrus pulp, in combination with livestock wastes, straw and cheese whey for biogas production. The aim of this work was to investigate the effects of two different bioenergy by-products on soil carbon stock, enzymes involved in nutrient cycling and microbial content. The two digestates were obtained from two plants differently fed: the first plant (Uliva) was powered with 60% of recalcitrant agricultural wastes, and 40% of livestock manure milk serum and maize silage. The second one (Fattoria) was fed with 40% of recalcitrant agricultural wastes and 60% of livestock manure, milk serum and maize silage. Each digestate, separated in liquid and solid fractions, was added to the soil at different concentrations. Our results evidenced that mixing and type of input feedstock affected the composition of digestates. Three months after treatments, our results showed that changes in soil chemical and biochemical characteristics depended on the source of digestate, the type of fraction and the concentration used. The mainly affected soil parameters were: Soil Organic Matter (SOM), Microbial Biomass Carbon (MBC), Fluorescein Diacetate Hydrolysis (FDA), Water Soluble Phenol (WSP) and Catalase (CAT) that can be used to assess the digestate agronomical feasibility. These results show that the agronomic quality of a digestate is strictly dependent on percentage and type of feedstocks that will be used to power the digester.

The Effects Of Humic Substances On Pinus Callus Are Reversed By 2,4-Dichlorophenoxyacetic Acid

The reversal of humic matter-induced inhibition of callus growth and metabolism by 2,4-dichlorophenoxyacetic acid (2,4-D) was studied in Pinus laricio. Two forest humic fractions (relative molecular mass (Mr) > 3500), derived from soil under Fagus sylvatica (Fs) and Abies alba (Aa) plantation, were used. Pinus laricio callus was grown for a subculture period (4 weeks) on Basal Murashige and Skoog (MS) medium plus forest humic matters (Fs or Aa), at a concentration of 1 mg C/l, and then was transferred, for an additional four weeks, to a MS medium culture without humic matter, but with different hormones: indole-3-acetic acid (IAA, 2 mg/1) or 2,4-dichlorophenoxyacetic acid (2,4-D, 0.5 mg/1) and/or 6-benzylaminopurine (BAP, 0.25 mg/1). Growth of calluse, glucose, fructose, and sucrose contents, and activities of soluble and bound invertases, glucokinase, phosphoglucose isomerase, aldolase, and pyruvate kinase were monitored. The results show a negative effect of humic fractions on callus growth, due to decreased utilization of glucose and fructose, and decreased activities of glycolytic enzymes. The effects are reversible. Substitution of humic fractions with 2,4-D+BAP or 2,4-D is followed by an increase of glycolytic enzyme activities and, consequently, by the utilization of glucose and fructose that induces a restart of growth. In contrast, the inhibitory effects of humic fractions persist when they are substituted with BAP alone, indicating that only the auxin 2,4-D is capable of reversing the negative effects. A possible competitive action on the auxin-binding site between 2,4-D and the chemical structures in the forest humic fractions is suggested.