Ethephon induced oxidative stress in the olive leaf abscission zone enables development of a selective abscission compound

Abstract

BackgroundTable olives (Olea europaea L.), despite their widespread production, are still harvested manually. The low efficiency of manual harvesting and the rising costs of labor have reduced the profitability of this crop. A selective abscission treatment, inducing abscission of fruits but not leaves, is crucial for the adoption of mechanical harvesting of table olives. In the present work we studied the anatomical and molecular differences between the three abscission zones (AZs) of olive fruits and leaves.ResultsThe fruit abscission zone 3 (FAZ3), located between the fruit and the pedicel, was found to be the active AZ in mature fruits and is sensitive to ethephon, whereas FAZ2, between the pedicel and the rachis, is the flower active AZ as well as functioning as the most ethephon induced fruit AZ. We found anatomical differences between the leaf AZ (LAZ) and the two FAZs. Unlike the FAZs, the LAZ is characterized by small cells with less pectin compared to neighboring cells. In an attempt to differentiate between the fruit and leaf AZs, we examined the effect of treating olive-bearing trees with ethephon, an ethylene-releasing compound, with or without antioxidants, on the detachment force (DF) of fruits and leaves 5 days after the treatment. Ethephon treatment enhanced pectinase activity and reduced DF in all the three olive AZs. A transcriptomic analysis of the three olive AZs after ethephon treatment revealed induction of several genes encoding for hormones (ethylene, auxin and ABA), as well as for several cell wall degrading enzymes. However, up-regulation of cellulase genes was found only in the LAZ. Many genes involved in oxidative stress were induced by the ethephon treatment in the LAZ alone. In addition, we found that reactive oxygen species (ROS) mediated abscission in response to ethephon only in leaves. Thus, adding antioxidants such as ascorbic acid or butyric acid to the ethephon inhibited leaf abscission but enhanced fruit abscission.ConclusionOur findings suggest that treating olive-bearing trees with a combination of ethephon and antioxidants reduces the detachment force (DF) of fruit without weakening that of the leaves. Hence, this selective abscission treatment may be used in turn to promote mechanized harvest of olives.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-017-1035-1) contains supplementary material, which is available to authorized users.

Chemical Defoliant Promotes Leaf Abscission by Altering ROS Metabolism and Photosynthetic Efficiency in Gossypium hirsutum

“…Many environmental stresses, such as drought, UV, chilling, salt, and pathogen attack and hormone treatment, can induce leaf abscission in plants [3,20,32,37]. ROS play an important role in plant growth and development, especially in stress tolerance [38].…”

“…ROS produced at the abscission zone site play an important role in regulating leaf abscission under drought stress in cassava (Manihot esculenta Crantz) [19]. Recent studies have found that ROS do not work in the fruit abscission zone of olives (Olea europaea L.), but only alter oxidative stress in the abscission zone of leaves and then mediate abscission induced by ethephon [20]. Previous studies have shown that insufficient carbohydrate accumulation and distribution can lead to flower and fruit abscission.…”

Comparative Proteomics Profiling Illuminates the Fruitlet Abscission Mechanism of Sweet Cherry as Induced by Embryo Abortion

“…Our proteomics profiling of sweet cherry abscising carpopodium showed bidirectional changes in the expression of the cell wall-related proteins, probably associated not only with the ongoing process of abscission but also with the progressive development of the organs that are not dropped (Table S4). However, it is worth noting that most of the enzymes involved in cell wall degradation showed a trend of up-regulation, including cellulose [3], pectinase [47], polygalacturonase [48], β-galactosidase [49], which play a major role in cell wall degradation. Moreover, the enzymatic activity of cellulose, pectinase and polygalacturonase were significantly higher than non-abscising carpopodium (Figure 2a).…”

Technological Parameters and Evaluation of Antioxidant Enzymes from Sugarcane (Saccharum spp.) when Applied Chemical Ripeners

“…Apesar da ligeira diferença, os cultivares de cana-de-açúcar diferiram, significativamente, em relação ao percentual de fibras: RB85-5156 (12,34 %) e RB85-5453 (12,48 %). Em relação ao efeitos de maturadores químicos, controle, etephon, etefon + glifosato, sulfumeturon-metil + glifosato, sulfumeturonmetil, glifosato, MTD, MTD + glifosato e etiltrinexapac proporcionaram matérias-primas com médias de Fib iguais a 12,03, 12,03, 12,41,12,19,12,98,12,68,12,39,12,63 e 12,32 %, respectivamente, indicando que os produtos, exceto etefon, intensificaram a deposição de lignina em colmos de cana-deaçúcar. 68 Pesquisadores sugerem que aplicações de MTD + glifosato e glifosato em cana-de-açúcar aumentam o percentual de Fib desta matéria-prima em 12,00 e 17,00 %, respectivamente, corroborando, parcialmente, os resultados deste estudo, que indicou que os mesmos tratamentos surtiram efeitos similares, porém menos intensos.…”

“…Todavia, há escassez de informações sobre reatividade de enzimas antioxidantes de cana-de-açúcar à aplicação exógena de maturadores químicos, produtos que exercem funções análogas às desempenhadas pelos hormônios vegetais endógenos, auxinas, giberilinas, citocininas e etileno. [14][15][16][17][18][19] Em cana-de-açúcar, são usuais as aplicações dos ingredientes ativos, glifosato, sulfumeturon-metil, etil-trinexapac e etefon (Figura 1), que, embora agreguem qualidades industrialmente requeridas à matéria-prima, são potencialmente capazes de depreciá-la, caso sejam manejados, inapropriadamente, devido à possibilidade de indução de estresses oxidativos a variedades comerciais, resultando em lavouras improdutivas. [20][21][22] Figura 1.…”