Leaf Calcium Content Research Articles

Potential for improving freezing stress tolerance of wild potato germplasm by supplemental calcium fertilization

The main objective of the present study was to investigate the influence of supplemental calcium fertilization on the levels of freezing tolerance in different wild potato species. For this purpose, the freezing tolerance of a broad spectrum of theSolatium taxa was evaluated with and without supplemental calcium fertilization. Previous studies have shown that there is a large variation in the calcium accumulation capabilities among species and among various accessions within species. While this study confirms such variation, no direct relationship between the leaf calcium content and the improvement in freezing tolerance was found. Nevertheless, overall 45% of the species accessions had significant higher leaf calcium content and 52% of the species accessions showed a significant drop in the frost score average at the p<0.05 level. In terms of this experiment, a drop in the frost scores meant an improvement to withstand cold. One third of the frost tolerant accessions and 41% of the frost sensitive accessions showed both, a significant increase in leaf calcium content and at the same time a significant lower average frost score. The different response observed among the accessions may suggest that even though most of the accessions are able to accumulate calcium, only some of them may have the ability to benefit from the supplemental calcium. Future breeding schemes may be able to use this information for selecting clones that would respond positively to calcium fertilization in terms of frost survival. Results of this study also suggest that calcium fertilization may be used as a rather inexpensive cultural practice for protecting potatoes from frost damage. The results of the present study also suggest that soil calcium levels should be taken into consideration when freezing tolerance of potato germplasm is being evaluated.

Foliar calcium concentration of potato and its relation to genotype lateness and tolerance of cyst nematodes

In field trials during three years respectively 18, 22 and 57 potato genotypes were grown on soils moderately or heavily infested with potato cyst nematodes (Globodera pallida) after soils were fumigated or not. Nematode infection increased leaf calcium contents but genotypes that were relatively tolerant of potato cyst nematodes (Globodera pallida) had lower leaf calcium concentrations on a particular sampling date. Tolerance of potato cyst nematodes was closely linked to genotype lateness and may be related to tolerance of drought. When using the method in plant breeding and screening for genotypes with tolerance, plants may be planted in infected or in uninfected soils, without influencing the outcome. The relationship between tolerance and calcium contents was clearest when sampling took place towards the end of the growing season when the variability was at it highest with a good distinction between newly formed leaves in late maturing genotypes and aged leaves in early maturing cultivars.

Irrigation with brackish water under desert conditions X. Irrigation management of tomatoes ( Lycopersicon esculentum Mills) on desert sand dunes

A series of trials were conducted over a period of three growing seasons in the Negev desert highlands of Israel to determine optimal conditions for irrigation of processing tomatoes (cultivar M82-1-8) planted on a sandy soil. Cultural conditions was the same for all trials. Tomatoes were drip irrigated with brackish (EC i = 6.2 dS m −1) and fresh (EC i = 1.2 dS m −1) water. In the first trial, the effect of irrigation frequency (twice a day, once a day, every second and every third day) was determined. Yields in the fresh and the brackish water treatments were similarly affected by one or by two irrigations per day. Irrigation every 2 and every 3 days significantly reduced yields in the two water quality treatments. On average, yields of brackish water irrigated plants were about 44% of yields from fresh water plants. The effect of three planting dates ( 15 3 , 1 5 , 15 6 ) on yields of fresh and brackish water irrigated tomatoes was investigated in the second season. Fresh water yields were similar for the first two planting dates but significantly reduced at the third planting date. Brackish water yields were reduced with each subsequent planting date. Relative yield of brackish water plants was 59%, 43% and 30% for the first second and third planting date, respectively. The detrimental effect of brackish water on tomato yield was completely overcome through the use of pulse-irrigation (five times per day). Pulse irrigation markedly reduced midday rhizospheric salt concentration (EC r) as compared with that of plants which were irrigated only once a day. Brackish water irrigation resulted in lower leaf water potential, higher crop stress index but had little effect on leaf carbohydrate content. Salinity had no effect on chloride concentration in leaves but more than doubled the concentration of sodium. It had little effect on leaf calcium content but reduced the levels of potassium and phosphorus.

Effect of nutrient calcium on the cell wall composition and digestibility of kikuyu grass (Pennisetum clandestinumHochst)

The effect of calcium in the nutrient medium on kikuyu grass (Pennisetum clandestinum Hochst), grown in a solution culture, was investigated. Calcium had no effect on the lignin content of leaf material, but decreased the lignin content per unit stem cell wall. Calcium appeared to have no significant effect on either the hemicellulose and cellulose content or on the ratio of constituent sugars of the hemicellulose fraction of both leaf and stem tissue. A high cell wall phenolic acid content in kikuyu leaves was associated with a high leaf calcium content. High calcium considerably increased the dry matter yield of kikuyu, but did not appear to improve its digestibility.

Título en español.

En este trabajo se presentan los resultados de un estudio en el que se determinó el efecto del pH del suelo y los factores de acidez relacionados con él, en la producción de plátanos, cultivar Maricongo, sembrados en la arcilla Los Guineos, un Ultisol de la zona montañosa húmeda de Puerto Rico. El estudio reveló en la plantilla una correlación significativa, r = 0.47, entre el pH del suelo y el número de frutas por racimo, y otra altamente significativa, r = 0.70, entre el contenido en calcio de las hojas, y el número de frutas. En el primer retoño no se registraron correlaciones significativas entre el pH del suelo y los factores de acidez relacionados y la producción de plátanos, ni entre el contenido en calcio de las hojas y la producción de los mismos. El cultivar Maricongo parece ser tolerante a niveles de pH bajos y a la correspondiente alta concentración de aluminio cambiable.