G. Pulgar

Improving the Mineral Nutrition in Grafted Watermelon Plants: Nitrogen Metabolism

Watermelon (Citrullus lanatus [Trumb.] Mansfeld cv. Early Star), was used as scion grafted onto three cultivars of pumpkin (Cucurbita pepo L. cvs. Brava, Shintoza and Kamel) used as rootstocks and ungrafted Early Star plants were used as control. The rootstocks showed a high capacity for N uptake and transport to the scion where N reduction and assimilation improved growth of the scion in grafted plants with respect to the control.

Yield improvement in zucchini under salt stress: determining micronutrient balance

Zucchini plants (Cucurbita pepo L. var. Moschata) grown in pots under greenhouse conditions were supplied with differing amounts of NaCl (0, 20, 40, and 80 mM). The foliar concentrations of Cl, Fe, Mn and Zn increased in response to rising NaCl levels. The Cu concentrations in leaves were highest in the 0 mM NaCl treatment. In fruits, concentrations of Cl, total Fe and extractable Mn increased with higher levels of NaCl. Fruit yield was increased only by NaCl at 80 mM. Length and fresh weight of fruit tended to increase with increasing NaCl rate, and fruit dry weight proved greatest at 80 mM. The activities of catalase and ascorbic acid oxidase assayed in fruits showed an inverse relationship with the salt concentrations applied. In this context, it is useful to determine the effect of NaCl on the micronutrient concentration, given that the improvement of crop watered with saline water enhances the micronutrient profile. Thus, at 80 mM NaCl treatment improved the micronutrient levels in the shoot, and significantly increased the micronutrient density in the edible part of this crop.

Zucchini growth, yield, and fruit quality in response to sodium chloride stress

Abstract Zucchini (Cucurbita pepo L. cv. Moschata) plants were grown in a pot experiment under greenhouse conditions at Almeria (Southeastern Spain) in 1994 and 1995. Sodium chloride (NaCl) added to the irrigation water at 0 (control), 0.25, 0.50, and 1.0 g L‐1 and complemented with a fertilizer solution. Yield was determined on number and weight (kg) of fruit per plant. The hidric content (%W) per fruit was calculated using fruit fresh and dry weights. Fruit diameter, fruit length, and fruit firmness were also measured. Electrical conductivity, soluble solids concentration, titratable acidity, and pH as well as non‐structural carbohydrates concentration were determined. Zucchini yield, quality, and quantity increased as NaCl concentration was increased to 1 g L‐1. This cultivar appears to suitable to be grown in coastal locations where soil and irrigation water contain salt concentration that limit the growth of other crops less tolerant to salinity.

Nutritional diagnosis of fig tree leaves

Abstract Fig trees (Ficus carica L. cv. Pellejo Duro) were sampled during four consecutive years (1992–95). Nutrient element concentrations, fruit yield, and optimal ranges for the nutrient elements and physiological parameters were determined.

Temperature in relation to phosphorus nutrition in Chinese cabbage.

Abstract Chinese cabbage plants [Brassica pekinensis (Lour) Rupr. cv. Nagaoka 50] were cultivated experimentally for two years (1993 and 1994) using a semi‐forcing technique of floating rowcovers, polyethylene (T1), polypropylene (T2), versus no floating row‐covers, control (T0). Five samplings were made, taking four plants per each replication and total phosphorus (P) (Ptotal), inorganic P (Pi), and calculated organic P (Porg) were determined as well as foliar acid phosphatase activity (FAPA). The aerial and root temperatures of the treatments T1 and T2 exceeded those of T0. The Ptotal concentration showed no significant variations with treatment, whereas the Pi concentrations increased in Ti and T2 and Porg decreased in both treatments with respect to T0. The FAPA was influenced a similar way as Pi, raising with temperature. The contents (mg plant‐1) of Ptolal, Pi, and Porg were greater in T1 and T2 than in T0, and this could be due to the fact that the highest temperatures (root and aerial zone) generated by the plastic rowcovers favored the absorption of P, thereby boosting FAPA and the fresh and dry weights, and yield.

Plant nitrogen characteristics of a semi‐salt‐tolerant zucchini variety to sodium chloride treatments

Abstract Plants of a Zucchini (Cucurbita pepo L. var. Moschata) cultivar considered to be semi‐salt‐tolerant were grown in artificial soil in 1‐m containers under greenhouse conditions with differing supplies of sodium chloride (NaCl) [0 (T0), 30 (T1), 60 (T2) or 120 (T3) g m‐2 plot‐1] during the entire growth cycle. These plants were used to determine the concentrations of nitrogen (N) forms and fractions, together with antagonistic anions in both leaves and fruits. The ammonium (NH4) concentration increased and nitrate (NO3) concentration decreased in both leaves and fruits, and chloride (Cl) concentration increased while sulphate (SO4) concentration decreased in both leaves and fruits with NaCl treatments. Organic‐N concentration in leaves increased according to the soil salinity treatments, while in the fruit there was a slight increase at low salinity, although values returned to those of the control when soil salinity increased. In leaves there was an increase in proline concentrations when salinity...

Salinity affects phosphorus uptake and partitioning in zucchini

Abstract Zucchini plants (Cucurbita pepo L. cv. Moschata) were grown in artificial soil in 1‐m3 containers under greenhouse conditions in order to determine how to improve the performance of this crop in an salinity‐affected agricultural area where there can be an enormous economic return with correction. Eight weeks after planting, four salinity treatments were initiated by the addition of 0, 20, 40, or 80 mM sodium chloride (NaCl) to the irrigation water. The leaves and fruits were collected and both total phosphorus (P) and inorganic P concentrations were measured. As salinity increased, total and inorganic P concentration in the leaf increased significantly. With the salinity increase, total and inorganic P concentration in the fruit was not affected. Total P content decreased in the skin and then returned to levels close to the control. In the fleshy part as well as in the whole fruit, however, increased salinity increased total P accumulation. Inorganic P content in the pulp increased significantly, while in skin and whole fruit, inorganic P content was not affected by the NaCl treatment. In our study, these P forms in the fruit showed that increased salinity augmented P accumulation, especially in the fleshy part where the accumulation of both P forms was not only more pronounced, but was also more directly related to increases in soil salinity. Thus, it is necessary to know what responses occur under such salinity conditions in order to improve the fertilizer management, and therefore crop performance, when dealing with this high ionic contamination.

Effect of nitrogen and potassium supply on concentration of iron and manganese and activities of catalase, peroxidase and aconitase in pepper plants

Abstract Pepper plants (Capsicum annuum L. cv. Lamuyo) grown in soil filled pots were fertilized with 4 levels of NH4NO3 (6, 12, 18 and 24 g/pot) and 3 levels of K2SO4 (4, 8 and 12 g/pot). The lowest concentrations (N1 and K1) were selected as controls. The foliar levels of Fe and Mn, both total and extractable, were measured, together with the activities of catalase, peroxidase and aconitase. The N and K treatments affected the Fe and Mn nutritional status of the leaves. The effects on the catalase and peroxidase activity showed an Fe‐Mn interaction more clearly than the concentrations of Fe and Mn in leaves. In the present experiment aconitase activity did not prove to be a good indicator for the Fe nutritional status of plants.

Pyruvate kinase activity as a bioind1cator of cations in grafted watermelon plants

Abstract Three cultivars of Cucurbita pepo L. were used as rootstocks (Brava, Shintoza and Kamel), and as scion part, four cultivars of Citrullus lanatus (Trumb) Mansfield (Sugar King, Early Star, Dulce Maravilla, and Sugar Bell) were grafted and subjected to the determination of calcium (Ca), potassium (K), sodium (Na), and magnesium (Mg), and pyruvate kinase activity in leaves. Control plants (not grafted) gave the highest level of total K with respect to the other cultivars. The cross Brava x Sugar Bell showed the higher K level, while the lowest was found with the cross Brava x Sugar King. Total sodium (Na) content did not show differences within the experimented crosses as 0.77 mg Na/g d.w. was obtained for all cultivars, while control plants gave levels of Na five times higher (3.49 mg/g d.w.). The cultivar Sugar King had the highest Ca integration capacity, whereas Dulce Maravilla showed a decrease, both with respect to the control plants. The results of soluble Mg were lower than those obtained in...

Effect of nitrogen and potassium on the ionic balance in Capsicum plants (Capsicum annuum L. c.v. Lamuyo).

Abstract Capsicum plants (Capsicum annuum L. cv. Lamuyo) were grown in controlled greenhouse conditions in artificial soil. The plants received increasing levels of N (6, 12, 18 and 24 g/m2) and K (4, 8 and 12 g/m2), complemented with other nutrients. On plants leaves sampled fortnightly throughout their growth cycle to measure the cations (C+: NH4 +, Na+, K+, Ca2+, Mg2+), anions (A: SO4 2‐, Cl‐, P2O4 ‐, NO), protons (H+), ascorbic and citric acid, and total organic anions. Our results showed an increase in foliar inorganic anions proportionnai to the NK doses applied. In general, citric acid gave a lower values in the lower NK doses, whereas, the higher values were obtained with the higher doses. No clear response was observed of ascorbic acid to the doses of NK as the highest leaf value was achieved, with the low NK levels. The internal cationic excess led to an increase in hydrogen ions, either extruded or integrated into the tissue. The values of the H+/Norg and C+‐A‐/Norg ratios increased as increased K1 to K3, with the combinations of N1, N2 and N3, with an inverse trend in N4.