María Concepción Martínez-Madrid

Polyamines, abscisic acid and ethylene production in tomato fruit

Abstract Tomato fruit of the fast-ripening cultivar Breton had higher rates of ethylene production than the slow-ripening cultivar Daniela. The initial abscisic acid values were high in both cultivars, but fell during the first six weeks of development. After this time the levels increased, reaching a maximum before ethylene production began to increase. This maximum was much more pronounced in the fast-ripening cultivar. The polyamine/ ethylene ratio also differed, with the slow-ripening cultivar having higher levels of putrescine and lower levels of ethylene. In this cultivar, putrescine was the major polyamine throughout, and it increased sharply during the ripening stage. Spermidine levels, on the other hand, decreased gradually, especially during the first two weeks of development.

Differential rind and pulp ripening of transgenic antisense ACC oxidase melon

1-Aminocyclopropane-1-carboxylic acid (ACC) oxidase (ACO) antisense Cantaloupe melons (Cucumis melo var. cantalupensis Naud.) unable to produce ethylene were used to identify the characteristic physiological processes occurring during ethylene-dependent ripening and to determine which tissue (pulp or rind) was most affected by this plant hormone. The antisense fruits were compared with untransformed fruits, which were used as controls. The most pronounced differences were observed in the rind when the untransformed melons entered in the climacteric respiratory stage. The major pigments, chlorophylls and carotenoids, remained undegraded, while sucrose and citric acid were accumulated continuously in antisense fruit rind. No big differences in the ripening parameters tested were observed in the pulp, except for those regarding the citric acid content and ripening index. The hypothesis of a differential ripening between pulp and rind in Cantaloupe melon is proposed.

1-Methylcyclopropene affects the antioxidant system of apricots (Prunus armeniaca L. cv. Búlida) during storage at low temperature.

BACKGROUND Apricots (Prunus armeniaca cv. Búlida) were treated with 1 μL L⁻¹ [corrected] 1-methylcyclopropene (1-MCP) immediately after harvest and stored in air at 2 degrees C for 21 days. Antioxidant levels (ascorbic acid and carotenoids), enzymatic antioxidant activities (superoxide dismutase (SOD) and unspecific peroxidase (POX)) and total antioxidant capacity (trolox equivalent antioxidant capacity (TEAC)) were determined. The level of oxidative stress was also established by measuring ion leakage during storage. The changes in the antioxidant potential of apricots were related to the capacity of 1-MCP to increase their commercial life. RESULTS 1-MCP-treated fruits exhibited higher SOD activity, whereas POX activity was significantly higher only after 21 days at 2 degrees C. Treated fruits also exhibited better retention of ascorbate and carotenoids and higher TEAC during storage. In accordance with these observations, lower ion leakage values were detected in 1-MCP-treated apricots. CONCLUSION Taken together, these results suggest that 1-MCP conferred a greater resistance to oxidative stress. This, along with the reduction in ethylene production, could contribute to the increase in commercial life and nutritional value observed in 1-MCP-treated apricots.

Behaviour of abscisic acid and polyamines in antisense ACC oxidase melon (Cucumis melo) during ripening

The behaviour of transgenic antisense 1-aminocyclopropane-1-carboxylic acid oxidase melon (TAM) was studied during fruit ripening. Work focussed mainly on analysis of the evolution of other plant growth regulators like ABA and polyamines in this type of melon. Physical-chemical and physiological differences from untransformed melon (UTM) (Cucumis melo L. var. cantalupensis Naud. cv. Védrantais) began to appear from the time of the latters ethylene crisis. Ethylene synthesis was inhibited by 97.7% in TAM at the time when UTM showed maximum ethylene levels. The ripeness index of TAM was lower, despite their higher soluble solids content, due to the higher titratable acidity. Unlike UTM, TAM rind maintained its colour and cell membrane integrity, although there was no difference in the pulp in this respect. Blocking ethylene biosynthesis affected the levels of ABA and the polyamine putrescine, the latter only in the rind. The possible relationship between ethylene, ABA and polyamines, the effect of blocking ethylene biosynthesis on the evolution of these regulators, and their role in fruit ripening are discussed.

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.

Influence of irrigation and organic/inorganic fertilization on chemical quality of almond (Prunus amygdalus cv. Guara).

The chemical quality of almonds variety Guara cultivated in nonirrigated farming (NI) and drip-irrigated farming (DI) conditions with different fertilizing treatments, two organic treatments (T1 and T2) and a mineral treatment (C), all of them with a N-P-K proportion of 1-2-1, is studied. Almonds obtained in irrigated farming showed higher content in sugars and organic acids and a better quality of oil. Among the fertilizing treatments employed, the organic ones have shown the best results related to chemical quality, regardless of the quantity of fertilizer employed (9.5 kg per T1 tree vs 4.5 kg per T2 tree). The organic treatments produced almonds with a higher content of sugar, organic acids and fiber and a similar fat content. These results are interesting from a commercial point of view since the consumers, even under the same conditions of chemical quality, prefer those products cultivated under organic conditions due to their benefits for health and because these practices are environment-friendly.