Vicente Almela

The synthetic auxin 3,5,6-TPA stimulates carbohydrate accumulation and growth in citrus fruit

The application of the synthetic auxin 3,5,6-TPA at the cell enlargementstage increased hexoses in developing fruit from foliated and fully defoliatedplants of Satsuma mandarin, cv. ‘Okitsu’ (Citrusunshiu Marc.). Although the sucrose concentrations also increased,ingeneral the differences were not statistically significant. The plant growthregulator reduced fruit abscission in defoliated trees while it stimulatedfruitgrowth in the foliated ones. The carbohydrate accumulation induced by 3,5,6-TPAindicates that its stimulatory effect on fruit growth might operate viapromotion of sink strength. The results also suggest the occurrence of pathwaysfor induction of fruit abscission, linked to carbon availability, relativelyindependent of the stage of development.

Loquat fruit size is increased through the thinning effect of naphthaleneacetic acid

The thinning effect of naphthaleneaceticacid was examined in loquat trees (Eriobotryajaponica Lindl.). The effect depended on theconcentration applied and on the treatment date. Themost effective treatment found to thin fruit andincrease the average fruit size was the application of20 mg l−1 of naphthaleneacetic acid 10–15 daysafter anthesis. Treatment reduced the fruit resistanceto puncturing and improved total soluble solidsconcentration and coloration and, consequently,harvest time was markedly advanced.

EFFECTS OF RINGING BRANCHES ON FRUIT SIZE AND MATURITY OF PEACH AND NECTARINE CULTIVARS

SummaryRinging branches at pit hardening resulted in larger fruits and enhanced fruit colouring of peaches and nectarines. Because both together determine the time of harvest, fruit from ringed trees were picked earlier. Further, ringing resulted in advanced fruit ripening compare with controls. Results obtained were similar to those reported for girdling. Ringing is easier and quicker than girdling and represents a useful technique to improve fruit quality.

Synthetic auxin 3,5,6-TPA promotes fruit development and climacteric in Prunus persica L. Batsch

SummaryThe application of 3,5,6-TPA advances fruit maturation of peaches and nectarines through different mechanisms, depending on the fruit development stage at treatment. Treatments applied at pit hardening encourage the development of fruit, which grow faster, reach the climateric stage earlier, and can be harvested earlier. The effect is direct, since the number of fruits per tree is not reduced by the treatment and also can be obtained by applying the auxin locally to a small number of fruits per tree. Treatments applied a few days before climateric increase ethylene production without affecting fruit growth.

Effect of the synthetic auxin 2,4-DP on fruit development of loquat

Application of the butylglycol ester of 2,4-DP increased final fruit size in loquat without causing fruit thinning. Its effectiveness depended on the concentration applied and treatment date. When applied at the onset of the cell enlargement fruit stage, 25 mg l−1 was the most effective treatment. Fruit diameter distribution showed a significant shift to the larger size for treated trees; further, fruit colour break and maturation were encouraged and harvest time was earlier than in untreated trees.

Auxin interaction with the vesicular-arbuscular mycorrhizal fungus Glomus intraradices Schenck & Smith improves vegetative growth of two citrus rootstocks

Abstract The vesicular-arbuscular mycorrhizal (VAM) fungus Glomus intraradices Schenck & Smith increased root and shoot growth of the citrus rootstocks sour orange ( Citrus aurantium L.) and ‘Carrizo’ citrange ( Citrus sinensis (L.) Osb. X Poncirus trifoliata (L.) Raf.). The application of indolebutyric acid (IBA) at 2.0 g l −1 as a 10 s root dip to non-mycorrhizal seedlings was ineffective in increasing growth, but application to mycorrhizal seedlings had a positive VAM-IBA effect on growth.

Rootstock influence on the incidence of rind breakdown in ‘Navelate’ sweet orange

Summary The influence of three rootstocks, Carrizo citrange (Citrus sinensis (L.) Osb. × Poncirus trifoliata (L.) Raf.), Cleopatra mandarin (Citrus reshni Hort. ex Tanaka) and sour orange (Citrus aurantium L.) on the incidence and severity of rind breakdown in ‘Navelate’ sweet oranges was studied over seven years in four orchards. The proportion of affected fruit was greater in trees on Carrizo citrange (60% on an average) followed by Cleopatra mandarin (38%) and then on sour orange (9%). There were also significant differences in the severity of the disorder among rootstocks; more than 35% and 20% of fruit from trees on Carrizo citrange and Cleopatra mandarin, respectively, were rejected for commercialization, whereas only 4% of fruit on sour orange was rejected. Cryo-scanning electron microscopy (SEM) of fruit peduncles showed that average diameter of xylem vessel elements of peduncles of fruits on Carrizo citrange rootstock were 6% and 17% larger than those on Cleopatra mandarin and sour orange, respectively. Defoliation of fruit-bearing branches reduced water loss from fruit, maintained fruit peel water potential at a higher value than that of fruit on undefoliated branches and reduced the proportion and severity of affected fruit. It is concluded that fruit-tree water relationships are related to rind breakdown in ‘Navelate’ oranges and low fruit water content might be responsible for the disorder.

The effect of 2, 4-DP on fruit development in apricots (Prunus armeniaca L.)

Abstract The application of 25 mg l−1 2, 4-DP (2, 4-diclorophenoxypropionic acid butylglycol ester) at pit hardening, increased final fruit size and advanced fruit maturation in apricots. Fifteen days after treatment the differences in diameter between control and treated fruit reached a maximum and remained constant until harvest. This effect coincided with a decrease in leaf weight and, at an advanced stage of development, leaf area. This suggests a competitive relationship between fruit development and vegetative growth, although a direct effect of 2, 4-DP on fruit development cannot be discarded.

Histological and physiological study of purple spot of loquat fruit

Abstract We describe the structure of purple spot of loquat (Eriobotrya japonica Lindl.) by comparison between affected and non-affected fruit, using light and scanning electron microscopy (SEM) procedures. Water permeability rates of isolated cuticles and mineral fruit composition were also measured. SEM and light microscopy show that purple spot initially appears at the deepest rind cell layers as a fringe of compact and empty cells. As purple spot intensity increases, the number of affected cells also increases to include all rind tissue. Affected cells show a shrunken cytoplasm with an extrusion of cellular material out of the plasmalemma. Flesh cells are not damaged. The cuticle of affected fruit showed no sign of damage or disruption and the water permeability of isolated cuticles showed no consistent differences between injured and healthy fruits. Mineral composition in flesh tissue of affected and healthy fruit was similar. However, in epidermal tissue concentration of K, Fe and Cu were higher in affected fruit than in healthy fruit.

Effects of fruit thinning on fruit growth, sugars and purple spot in loquat fruit (Eriobotrya japonica Lindl.)

Summary This work examines the effects of fruit thinning on fruit growth, sugar accumulation and incidence of purple spot in loquat (Eriobotrya japonicaLindl.). Thinning increased fruit growth and sugar contents of fruit. As total sugar concentration correlated significantly with the proportion of affected fruit, we conclude that thinning increased markedly the proportion of fruit affected by the disorder. Carbohydrate accumulation may be the factor responsible for the incidence of purple spot by accelerating fruit development.