Effects of an Auxin and a brassinosteroid on physical, chemical and biochemical attributes of ‘Galaxy’ apples

Abstract

The aim of this study was to study the effect of the auxin naphthalene acetic acid (NAA) and the brassinosteroid 28-homocastasterone (28-HCS) applied every 15 days (harvest 2015/16) or every 21 days (harvest 2016/17) after full bloom, on the physical, chemical and biochemical attributes of the ‘Galaxy’ apples. The study was performed at a commercial orchard at Vacaria county, Rio Grande do Sul State, Brazil. The following treatments were applied: water (control), NAA (0.1%), 28-HCS (10‒6 M) and NAA (0.1%) + 28-HCS (10‒6 M). For this purpose, 300 μL of the plant growth regulator solutions were applied to the fruit peduncles. Fruits treated with NAA every 21 days presented higher starch-iodine index and lower total soluble solids (TSS), titratable acidity (TA), lightness index (L) and hue angle (h°) than 28-HCS-treated fruits. Fruits treated every 15 days with NAA presented reduced skin rupture force (SRF), total antioxidant activities (TAA) of the skin and flesh, and hydrogen peroxide content compared to the control fruits. In addition, NAA application every 15 and 21 days resulted in increased anthocyanin content in the skin. Application of NAA + 28-HCS reduced superoxide dismutase activity. 28-HCS applications increased TSS, color attributes (C and h°) of the skin, total antioxidant activity of the skin and flesh and peroxidase activity compared to control fruits. These results are expected to help to understand how plant growth regulators affect apple quality. In addition, results described here are also expected to help on the development of strategies to reduce post harvest losses and to increase fruit shelf life.

The application of 28-homocatasterone brassinosteroid reduces blossom end rot in ‘BRS Montese’ tomatoes

“…Changes in cell wall components, especially cellulose, hemicellulose, and pectins affect texture modifications. Adequate Ca concentrations in fruit tissues promote the maintenance of texture, firmness, and resistance to damage as well as the reduction in the senescence process of the fruits (RAMOS et al 2019).…”

“…However, fruits treated with 28-homocatasterone had lower h° values in the region more exposed to solar radiation, indicating a greater intensity of the red color in fruits (Table 2). The application of 28homocatasterone possibly induced greater expression of PSY-1 genes, responsible for carotenogenesis at the expense of PSY-2 (predominant in green tissues), increasing the activity of enzymes involved in the biosynthesis pathway of pigments, such as lycopene (RAMOS et al 2019).…”

“…Brassinosteroids (BRs) are hormones produced by plants that play an important role in plant development (TAIZ & ZEIGER 2017). In plant tissues, BRs promote the organization of cellulose microfibrils and the regulation of cell division and expansion, besides increasing the contents of soluble solids and phenolic compounds in fruits (PLANAS-RIVEROLA et al 2019, RAMOS et al 2019. BRs also act in the formation of xylem vessels, regulating the procambial cell differentiation and tracheal elements (TAIZ & ZEIGER 2017).…”