J. L. Valenzuela

Influence of plant age on mature leaf iron parameters

Abstract The change of several biological and physiological indicators was studied in mature leaves of muskmelon plants (Cucumis melo L. cv. Galia) during the biological cycle. Plants were grown under greenhouse conditions, using differential fertilization with N, P, and K, and irrigation with brackish water. We measured total and soluble Fe and Mn, total and soluble Fe index, endogenous and Fe‐ and Mn‐inflitrated catalase and peroxidase and aconitase activities in leaves in an attempt to trace possible Fe deficiencies. The Fe‐Index is defined as follows: Fe Index = [(10P + K) 50]/Fe, where: P and K as % d.w. and Fe as μg/g d.w. The physiological indicators (Fe Index) was markedly raised at the beginning of the biological cycle, indicating that foliar samples contained high concentrations of P and K, which may have induced Fe deficiency. The Fe Index decreased steadily during the biological cycle, indicating that fertilizer was applied correctly. Comparisons of endogenous and Fe‐ and Mn‐infiltrated enzyma...

Variations in nutrient levels in watermelon cultivars irrigated with saline water: total ions

Abstract Few studies have been published on nutritional parameters in greenhouse cultivated watermelon despite the importance of this species in the human diet. It was therefore considered worthwhile to study some of the cultivars soon to become commercially available in Spain to determine which of them are best suited to cultivation in areas along the Mediterranean coast. All ten cultivars of Citrullus lanatus (Trunb) Mansfield studied were grown in polyethylene covered greenhouses. Four replications of each cultivar distributed in random blocks. Leaves were sampled every 15 days during one complete biological cycle to determine total macro‐ and micro‐nutrients. These data ere then related to productivity (fruit yield). The different cultivars presented marked differences in both macro‐ and micronutrient levels: total N in Perla‐Negra (Black Pearl) was twice that found in Tolerant, while total K in Resistent was double that in Candida. Total proteins also differed significantly between cultivarss as did ...

Influence of nitrogen, phosphorus, and potassium fertilization on foliar pigments in muskmelon plants

Abstract The effect of nitrogen (N), phosphorus (P), and potassium (K) fertilization on chlorophyll a and b, carotenes, and anthocyanin was studied in muskmelon plants (Cucumis melo L. cv. Galia) during their biological cycle. Plants were grown under greenhouse conditions using differential fertilization with N, P and K, and irrigation with brackish water. We measured chlorophyll a and b, carotenes, anthocyanin, and total and soluble magnesium (Mg) and iron (Fe) contents. No relationship was found between the rate of fertilizer applied and the content of these pigments. Our results revealed that a relationship does exist between the foliar content of chlorophyll a and Fe, irrespective of the fertilizer treatment applied. However, only a relationship between chlorophyll b and Mg in the P treatments was found. The fact that the chlorophyll content was related to the N and K treatments could be due to a slight deficiency induced by Mg. The phenological stage of specific parameters was studied, resulting in t...

Foliar diagnosis: vegetative index for several cultivars of watermelon

Abstract Monitoring the nutrient status of a crop by tissue analysis is an important tool in maximizing yields and avoiding nutrient deficiencies or toxicities. Ten cultivars of watermelon [Citrullus lanatus (Trunb) Mansfield] were grown under the same fertilization regimen throughout their growth cycle and were sampled fortnightly in order to determine total and soluble macronutrients. Cultivars grown under favourable greenhouse conditions had different but generally high nutritional requirements. The data from total and soluble vegetative index [relation between mobile nitrogen (N), phosphorus (P), potassium (K), and immobile calcium (Ca) and magnesium (Mg)] were used to distinguish between different cultivars. In every cultivar, soluble vegetative index was high respect to the total index.

RELATIONSHIPS BETWEEN NITROGEN SUPPLY AND DIFFERENT PHOSPHORUS AND CALCIUM FRACTIONS IN LEAVES OF TOMATO AND CUCUMBER PLANTS

ABSTRACT Tomato and cucumber plants were grown in a greenhouse with different N treatments (N1 7.5; N2; N3: 20; N4: 30 g/m2). Leaves were sampled every two weeks throughout the period of maximum fruit production to determine the different P fractions (inorganic P, organic P, lipidic P, RNA P, DNA P, and proteic P) and Ca fractions (soluble Ca, bound Ca, inorganic insoluble Ca, and organic insoluble Ca), obtained by extraction with different solvents. Inorganic and organic P were the largest fractions, representing 70% of total P in tomato (vs 10% RNA P; 8% of lipidic P; 7% of DNA P, and 5% of proteic P) and 55% in cucumber (vs. 15% of RNA P; 13% of lipidic P; 10% of DNA P, and 7% of proteic P). The highest concentration of lipid P was found with treatment N2 in both crop species. The organic insoluble Ca fractions together with the inorganic insoluble fraction made up 50% (tomato) and 80% (cucumber) of total Ca. Relationships between P and Ca fractions and macro-micronutrients were also studied. A positiv...

What constitutes a good iron indicator with brackish water and gypsum

Abstract Solanum rnelongena plants (eggplant/aubergine) were grown under greenhouse conditions in an artificial soil enriched in CaSO4 and organic matter, and fertilized with N and P in the irrigation water, which was strongly brackish. Physiologically mature leaves were sampled every 15 days to analyze physiological and biochemical parameters. The results showed that, given the rhizospheric conditions in our experiments, there was an increase in Mn at the expense of Fe, and total Fe index was influenced by total P and K concentration, and, to a lesser degree, by total Fe. In contrast, the soluble Fe index was most markedly affected by soluble Fe, which was the most influential component of this index. The Fe index is defined as follows: Fe index = (10P + K)50/Fe, where Fe = μg iron/g dry matter, P = % phosphorus in dry matter, and H = % potassium in dry matter. The total Fe index is calculated from total nutrients, whereas the soluble Fe index is obtained from soluble nutrients. Enzymatic activities fail...

Effects of nitrogen, phosphrous and potassium treatments on phosphorus fractions in melon plants

Abstract The effects of nitrogen (N), phosphorus (P), and potassium (K) treatments on the P fractions in muskmelon plants (Cucumis melo L. cv. Galia) are presented. Plants were grown under greenhouse conditions with different NPK treatments. Leaves were sampled every two weeks from the middle third of each plant. After washing in nonionic soap and distilled water, the leaves were dried in an oven at 70°C and then ground. The foliar contents of several P fractions [inorganic P (Pinorg), organic P, lipid P, RNA‐P, DNA‐P, and proteic P] were determined. Inorganic and organic P were found to be the major fractions. For both N and K treatments, the Pinorg content increased, although at high doses (N24 and K30), there was a reduction in leaf content. With the P treatments, the contents of the fractions increased steadily, but with the highest doses (P15 and P20), the leaf content of the fractions was very similar, indicating a saturation phenomenon. Evolution of the fractions over time showed similar behavior. ...

Concentrations and ratios of total and hydrochloric acid‐extractable micronutrients in leaves of several cultivars of muskmelon

Abstract Iron (Fe) index was studied in 19 cultivars of muskmelon (Cucumis melo L.) throughout a growth period. All cultivars were grown under greenhouse conditions and were sampled each 15 days. Leaf material was analyzed in order to determine total and hydrochloric acid (HCl)‐extractable micronutrient concentrations in leaves. Total iron (Fe) content was particularly high in cv. Galia and low in cv. Amarillo Canario. Cultivar Cantaloupe showed the highest levels of total manganese (Mn) and zinc (Zn) while lowest of total Mn were recorded in cv. Arava, and lowest total Zn content in cv. Alma. Cultivar Gold‐King showed the highest foliar levels of total copper (Cu), and this micronutrient was lowest in cv. Hum. 2627. Greater differences between cultivars were noted in terms of HCl‐extractable micronutrients. Bayon and Num. 1213 showed very low values for total Fe index, which was highest in Amarillo Canario. Optimal nutritional ranges in the cultivars analyzed were variable but generally high for micronut...

Ion balance and its evolution in cultivars of melon (cucumia melo L.) irrigated with brackish water

Abstract The present study compares ionic balance in 19 muskmelon cultivars grown under greenhouse conditions with the same system of fertilization‐irrigation. Each cultivar was studied in 4 replications distributed in a random block design. In all 20 plants were sampled in each replication of each cultivar every 15 days throughout the reproductive cycle, and analyzed inmediately afterward. Highly significant differences were noted for cations (C+) (Gold‐King 304 meq/100g d.w., Canario 183 meq/100g d.w., anions (A‐) (Cantaloupe 387 meq/100g d.w., Arava 272 meq/100g d.w.), and cations‐anions balance (C+‐A‐) (Gold‐King ‐6 meq/100g d.w., Rocher ‐157 meq/100g d.w., Canario ‐163 meq/100g d.w.), as well as for hydrogen ions (H+) forming capacity (Dorado and Gold‐King 88 meq/100 g d.w., Gallicum, Rocher and Canario 0 meq/100g d.w.). Differences in OH‐ formation were also notable (Polidor 243 meq/100g d.w., Makdimon 120 meq/100g d.w.). Consequently, fruit production among the different cultivars varied widely. Th...

Relationship between biochemical indicators and physiological parameters of nitrogen and physiological plant age

The families, Solanaceae and Cucurbitaceae, differ mainly in the size of the sink and the length of their biological cycle, although their phenological stages overlap in time to some extent. Leaves were sampled during the period of greatest metabolic activity, which coincided with a plural of morphological changes, in order to analyze nitrogen indicators and parameters. Nitrogen concentration decreased over time in the leaf, as did NO3-ions, dry weight, amino acids, total and soluble protein. NH4-ions, nitrate reductase and productivity peaked during the period of greatest metabolic activity, coinciding with flowering and the initial and final phases of fruit ripening, and were lowest during foliar senescence. Total and soluble vegetative index (relation between mobile N, P, K and immobile Ca, Mg) declined, and transient alterations coincided with certain morphological and metabolic changes. All physiological alterations during the different physiological stages were seen in both species regardless of the size of the sink, however the magnitude of the alterations was conditioned by the sink and by exogenous arid endogenous N levels. Organ senescence can be defined as a series of metabolic changes in the mature plant which include a decrease or increase in enzymatic activity, proteolyis, pigment degradation and death.