Search

Previous studies have reported that trinexapac-ethyl (TE) stimulates growth of well-watered (WW) eucalypt plants. However, the physiological and hormonal changes in response to this chemical remain unclear. Furthermore, there are reports that this chemical attenuates drought responses in grasses. This research investigated the hormonal and physiological response of Eucalyptus urograndis (Clone 1407) plants treated with TE, cultivated under WW and drought conditions. The experiment was carried out in a greenhouse up to 42 days after application of 0, 90 and 150 g ha−1 of TE. Eucalypt growth, hormone concentration, gas exchange, maximum quantum yield of photosystem II and total relative chlorophyll content were evaluated. TE increased growth of WW plants by up to 65%. Drought restricted the stimulatory effects of TE on eucalypt growth, despite an increase of at least 102% in gibberellin A 4 (GA 4), trans -zeatin (tZ) and N 6-isopentenyladenine (iP) concentrations after application. GA 4 stood out as an indicator of drought stress as it increased almost 6-fold compared to WW eucalypt. TE caused a hormonal imbalance in eucalypt up to 42 days after application, increasing GA 1 concentration as a short-term effect (8 days) and GA 8 as a medium-term effect (42 days). Gibberellin homeostasis was not reestablished until 42 days after TE treatment. These results provide insights into eucalypt hormonal response to TE. Future research should be conducted under field conditions to understand how long such positive effects would be detected over time in short-rotation eucalypt plantations. • Trinexapac-ethyl increased well-watered eucalypt growth by up to 65%. • Trinexapac-ethyl increased GA 1 biosynthesis as a short-term effect, followed by GA 8. • Gibberellin A 4 stood out as a drought stress indicator, increasing almost 6-fold. • Under drought, trinexapac-ethyl increased cytokinin biosynthesis, which may lessen the stress. • Drought restricted stimulatory effects of trinexapac-ethyl on growth. [ABSTRACT FROM AUTHOR] more...

Eucalyptus plants are sensitive to abiotic stresses in their initial growth, and nutritional deficiency is one of the most recurrent among them. Trinexapac-ethyl, which is a plant growth regulator, can positively affect eucalyptus, a response known as hormesis, possibly providing plants with greater tolerance to stress. The objective of this study was to evaluate the effect of trinexapac-ethyl at two application times, before planting (BP) or after planting (AP), in Eucalyptus urophylla under conditions of nutritional deficiency (NPK). Two experiments (one for each application time) were conducted simultaneously during 81 days after planting of eucalyptus in 15 L pots. The treatments consisted of three doses of trinexapac-ethyl (0, 30, and 60 g a.i.·ha−1) and four variations of nutrient supply: complete solution (NPK) and solutions without nitrogen (−N), without phosphorus (−P), and without potassium (−K). The variables of gas exchange, growth, and dry matter were evaluated. For both application times, trinexapac-ethyl had a positive effect on the root-shoot ratio of plants grown in −N and also positively affected some eucalyptus photosynthetic characteristics. In the AP application, the compound provided gains in height and dry matter, regardless of the nutrient supply. Under phosphorus deficiency, trinexapac-ethyl provided gains in total dry matter (BP) and leaf area (AP). [ABSTRACT FROM AUTHOR] more...