Asunción Amorós

Changes in ethylene evolution and polyamine profiles of seedlings of nine cultivars of Lactuca sativa L. in response to salt stress during germination

Abstract Lettuce seeds from nine cultivars were germinated under control and saline (150 mM NaCl) conditions. The effect of salt stress on germination, growth, ethylene production, respiration rate and polyamine levels was investigated. Salinity delayed germination and reduced the growth of all studied cultivars, but only significantly reduced final germination percentage in Inverna and Baby Star cultivars, while the other seven cultivars reached 100% germination under saline conditions. Respiration rate and ethylene production increased with salinity in all the nine lettuce cultivars. Moreover, cultivars that had a higher increase in ethylene production under salt stress showed the lowest reduction in fresh weight. The presence of salt reduced putrescine (Put) level, while spermidine (Spd) and spermine (Spm) increased. The effects of salinity on ethylene production and polyamine metabolism are discussed in relation to salinity tolerance of lettuce seedlings. The possible role of ethylene and polyamines as physiological markers for salinity tolerance in lettuce seedlings is also discussed.

Physico-Chemical and Physiological Changes during Fruit Development and Ripening of Five Loquat (Eriobotrya Japonica Lindl.) Cultivars:

Physico-chemical and physiological changes during development and ripening of five loquat cultivars (Eriobotrya japonica Lindl., cv. Algerie, Cardona, Golden, Magdall and Peluche) were determined. Fruit growth showed a sigmoid curve in all loquat cultivars. A good relationship between duration of fast growth phase and fruit size was found. In addition, a positive correlation was also established between seed number and fruit size, and between seed weight and both fruit and flesh weight. Colour changes, sugar content increase and the decrease in fruit firmness and organic acids started simultaneously when loquat fruits were in the phase of fast growth, and at about 70-80% of their final weight. These physico-chemical changes related to fruit ripening coincided with an increase in both ethylene production rate and free and total 1-aminocyclopropane-1 -carboxylic acid (ACC) content in the flesh. In addition, a small respiration peak associated with ripening was also detected. These results indicated that loquat fruits of all five studied cultivars showed a pattern of ripening in the tree that could be classified as climacteric, with relatively low ethylene production evolving at an early phase of fruit development.

Antioxidant and Nutritional Properties of Date Fruit from Elche Grove as Affected by Maturation and Phenotypic Variability of Date Palm

Some parameters related to nutritive and functional properties were evaluated in date fruit from seven date palms from the Elche grove along the maturation process, in order to obtain information about differences due to phenotypic variability. Results showed that sugar and organic acid concentration were different depending on date palm, the highest levels being reached at 100% Rutab stage, with glucose and fructose as the predominant sugars and malic acid as the major organic acid. Hydrophilic total antioxidant activity (HTAA) was high and correlated to phenolic content, with maxima levels being found at early, medium or late Khalal stages, depending on date palm. In addition, significant differences were found in both, phenolic concentration and HTAA among date palm and maturation stages, while lipophilic total antioxidant activity (LTAA) was very low, without changes along maturation and not correlated to HTAA. Then, date fruit from Elche grove could serve as a good source of natural antioxidant and it would be advisable to consume them at medium or late Khalal stages, in order to achieve the maxima nutritional (high concentration of sugars and organic acids), organoleptic (appropriated firmness levels, yellow or red color and low astringency) and functional properties with benefits to human health.

NON-INVOLVEMENT OF ACC AND ACC OXIDASE ACTIVITY IN PEPPER FRUIT RIPENING

Abstract Pepper of the variety California shows sigmoid-type growth curves and changes of colour, which are characteristic of the fruit reaching maturity, when it has practically reached full size. Respiratory activity is high a few days after fruit-set and then falls progressively. Ethylene production and 1-aminocyclopropane-1-carboxylic acid (ACC) levels remain low throughout fruit development and maturation, while ethylene-forming enzyme (EFE) activity gradually falls throughout the development. We show that treatment with propylene has no effect on the post-harvest maturation of pepper, although treatment with silver thiosulphate (STS) increases respiratory intensity and ethylene production due to the stress caused which, in turn, causes an increase in ACC levels after treatment. All these results lead to the conclusion that pepper behaves like a non-climacteric fruit during maturation, and that maturation is not regulated by ethylene.

Physicochemical changes during date ripening related to ethylene production

Some physicochemical parameters related to ripening and their relationship with ethylene were studied in date fruits (Phoenix dactyliferaL. type Negros). Dates were harvested and classified into sixteen ripening stages according to their color, ranging from yellow-greenish to dark brown. Fruit firmness decreased through the different ripening stages, while the ripening index, expressed as the relation between soluble solids and acidity, increased. The greatest loss of fruit firmness correlated with the greatest increases in both polygalacturonase and •-galactosidase activities. In early ripening stages, a small peak in ethylene production was detected, followed by a peak in respiration rate, suggesting that a date could be considered as a climacteric fruit, with the plant hormone ethylene being responsible for changes in color, fruit firmness, soluble solids content and acidity.

PRESERVATIVE SOLUTIONS CONTAINING BORIC ACID DELAY SENESCENCE OF CARNATION FLOWERS

We investigated the effect of a preservative solution containing boric acid on the senescence of cut carnation flowers (Dianthus caryophyllus L. cv. Master). A 24-h pulse treatment with the preservative solution containing 50, 75 or 100 mM boric acid or continuous treatment with 1 mM boric acid resulted in strong inhibition of the climacteric ethylene production. Both the pulse and continuous treatments significantly increased flower longevity. Free and conjugated 1-aminocyclopropane-1-carboxylic acid (ACC) and ACC oxidase activity increased in carnation petals during senescence, although significantly less in boric acid-treated carnations than in control flowers. The levels of putrescine increased as senescence progressed in both control and boric acid-treated carnations and an increase in spermidine levels was higher in treated carnations. Abscisic acid levels in petals also increased during senescence, but much less in boric acid-treated carnations. It is concluded that boric acid prevents the early rise in ethylene production and considerably improves carnation vase life.

Effects of brassinosteroid analogues on total phenols, antioxidant activity, sugars, organic acids and yield of field grown endive (Cichorium endivia L.).

BACKGROUND Cichorium endivia L., either cooked or eaten raw in salads, is a favourite cultivated vegetable around the world and the popularity is attributed to its healthy properties, which are mainly due to its high levels of antioxidant compounds and high content of minerals, provitamin A and vitamins. Brassinosteroids are a family of hormones that are found in plants and which serve as potent growth promoters. The effects of two brassinosteroid analogues, DI-31 and DI-100, were evaluated at concentrations of 4, 8 and 12 ppm together with a seaweed extract and amino acid mixture called Tomex Amin to enhance their activity. RESULTS All treatments with DI-100 and DI-31 resulted in the highest production increases. The chemical variables related to endive quality, such as moisture, carbon and nitrogen content, sugar and organic acid content were similar in the control and treated endives. Total antioxidant activity and total phenols increased significantly in endive treated with brassinosteroid analogues. CONCLUSION The results showed that sprayed brassinosteroid analogues mixed with Tomex Amin may play an important role in increasing the yield and the contents of total antioxidant activity and total phenols of field grown endives.

Physico-chemical and physiological changes during fruit development and on-tree ripening of two Spanish jujube cultivars (Ziziphus jujuba Mill.).

BACKGROUND Few studies have been performed on changes in organoleptic, nutritive, functional, and physiological properties during jujube fruit development and on-tree ripening. In this work, a comparative study on the evolution of physical, chemical, nutritive, and physiological parameters and bioactive compounds of two Spanish jujube cultivars was performed. RESULTS Both cultivars showed a non-climacteric ripening pattern, although the JM cultivar was smaller, sweeter, softer, and more highly coloured than the JG, which was characterised by having larger and firmer fruits, although less sweet and coloured. Both cultivars showed high TAA, which was highly correlated with the concentration of total phenols, giving them great functional properties. CONCLUSION This fruit has little economic importance in Spain and it is just marginally grown for self-consumption or for ornamental purposes. Given the excellent properties of these fruits, it could be considered a fruit species of great interest, and commercial growth of these cultivars with high yields and fruits with high functional properties should be promoted.

Brassinosteroids roles and applications: an up-date

Abstract Brassinosteroids are plant steroidal compounds involved in many functions related with plant development, metabolism, signalling and defense against a wide range of biotic and abiotic stresses. Plant architecture, which has a major effect on crop yield, is strongly influenced by brassinosteroids action. Brassinosteroids are recognized as key regulators of plant growth and development involved in a broad spectrum of processes at the molecular, cellular, and physiological levels. These roles suggest that many of the constraints of present agricultural production might be alleviated by manipulation of genetic determinants dealing with brassinosteroids, as well as by its exogenous application. Brassinosteroids are natural, nontoxic, non-genotoxic, biosafe, and eco-friendly, and can therefore be used in agriculture and horticulture to improve the growth, yields, quality, and tolerance of various plants to biotic and abiotic stresses. The present paper comprehensively reviews the latest results in the field of brassinosteroids and envisages future impacts in agriculture.

Date Palm Status and Perspective in Spain

The date palm (Phoenix dactylifera L.) is an archaeophyte in Spain and is the iconic species of an introduced mixed irrigated agricultural system of food crops, animal feed, grasses, and livestock. Traditionally, date palms are propagated from seed and grown for their fruits, as well as for products derived from the leaves and stem wood. The seedling date palm populations in Spain represent a diverse pool of genetic resources with potential to improve the crop in general. Depending on the local microclimate, 20–50 % of date fruits in Spain do not fully ripen on the tree because of cooler temperatures late in the growing season. Artificial ripening techniques have been devised to deal with this situation. Local genotypes are under study for the best fruit types for expanded marketing, as a gourmet fresh fruit product in Europe, to enhance farmer income and to sustain the traditional production system. Tissue culture of selected genotypes is contributing to sustainability of the palm groves. New commercial date products are under study to broaden economic possibilities. The exotic red palm weevil pest represents the main threat to the palm grove and control measures are being pursued. Historic palm groves persist in Spain, especially in Elche and Orihuela, as well as presumably naturalized feral palms exhibiting distinctive morphological characteristics described as P. iberica. Phoenix palms are protected and continue to provide commercial fruits and palm leaves for religious ceremonies and to enhance the local landscape. Elche, the largest palm grove, is a World Heritage Site and a major tourist attraction.