Abstract
This study aimed to evaluate the physiological response of Eucalyptus citriodora Hook seedlings subjected to foliar application of potassium phosphite and water deficit with the aid of multivariate statistical analysis, using MANOVA and canonical discriminant analysis. The experiment was conducted in a completely randomized design with five treatments (0.0 L c.p. ha-1 of potassium phosphite with irrigation; 0.0; 1.25; 2.50 and 5.00 L c.p. ha-1 of potassium phosphite without irrigation) and six replicates, in a greenhouse located in the municipality of Cruz das Almas, Bahia, Brazil. Treatments with potassium phosphite were applied by foliar spray, using the commercial product Reforce from Agrichem® (25.0% K2O + 35.0% P2O5 p/v). Irrigation was suspended seven days after application of the product. The correlation (0.6603) between the evaluated variables indicated that the use of multivariate analysis techniques was adequate to analyze this data set. Eucalyptus plants of the control treatment without irrigation responded to the water deficit conditions with inhibition of photosynthetic activity and increase of free proline content in the leaves. On the other hand, plants which received foliar application of potassium phosphite at highest concentrations (2.50 and 5.00 L c.p. ha-1), even under water deficit conditions, preserved the photosynthetic activity and proline content in the leaves with values equal to those observed in the irrigated control treatment. From this result it is possible to infer about the role of potassium phosphite as an attenuating effect of the water deficit in Eucalyptus citriodora Hook.
Highlights
The expansion of forests planted with the genus Eucalyptus in Brazil results from a series of factors which favor its large-scale planting, especially its fast growth, high yield and quality of wood, besides being a genus with many species and varieties adapted to the various conditions of climate and soil
The results of the multivariate analysis of variance (MANOVA) with the values of Roy’s largest root multivariate test = 1.9073 (F = 5.0068; p = 0.0014 < 0.05) showed significant difference between the means of the treatments, revealing dissimilarity between E. citriodora Hook plants for the variables evaluated
The phenotypic correlation between the variables evaluated showed that the significantly and positively correlated variables (P < 0.0001) were YII and ETR (r = 0.66; p = 0.0001), Fm and Fv/Fm (r = 0.48; p = 0.0075), F0 and Fm (r = 0.47; p = 0.0087), whereas the variables YII and YNPQ (r = -0.84; p = 0.0001), YNPQ and ETR (r = -0.52; p = 0.0034) and F0 and Fv/Fm (r = -0.49; p = 0.0397) were negatively correlated (Figure 3). These results indicate that the effective quantum yield of photosystem II (PSII) (YII) increases with the increase of electron transport rate
Summary
The expansion of forests planted with the genus Eucalyptus in Brazil results from a series of factors which favor its large-scale planting, especially its fast growth, high yield and quality of wood, besides being a genus with many species and varieties adapted to the various conditions of climate and soil. Due to these characteristics, eucalyptus has consolidated itself in the Brazilian forestry sector and currently its plantations occupy 5.7 million hectares of the area of planted trees in the country, and a large part is concentrated in the state of Bahia (IBÁ, 2017).
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