No abstract

Different types of sealing and sucrose concentrations influence in vitro elongation and adventitious rooting. Higher gas exchange (CO 2) favors the in vitro plant growth. The autotrophic system for the in vitro cultivation of Eucalyptus dunnii was not efficient.

Background: In vitro growth and development of plants in the micropropagation stages are influenced by several factors, including the light spectral quality, which has shown important effects on the photomorphogenesis. The work aimed to evaluate the photomorphogenic effect of spectral qualities on in vitro culture of Eucalyptus dunnii and Eucalyptus grandis × E. urophylla. Methods: Six light spectral qualities (i.e., red, white, blue, yellow, purple, and green) on in vitro multiplication, elongation, and adventitious rooting stages were evaluated through analysis of variance followed by a Tukey’s test. Results: White spectral quality was most adequate for in vitro multiplication of Eucalyptus dunnii and Eucalyptus grandis × E. urophylla, as it resulted in less tissue oxidation, longer shoot length, and more buds per explant. Red, blue and yellow spectral qualities increased the chlorophyll a, chlorophyll b, and total chlorophyll (a+b) leaf contents of Eucalyptus dunnii. To promote in vitro elongation, white spectral quality was most suitable for Eucalyptus dunnii, and yellow for Eucalyptus grandis × E. urophylla, as these resulted in more shoot length and shoots per explant. Red, white, blue and purple spectral qualities increased the stomatal density of Eucalyptus dunnii; while the white and yellow were the better for Eucalyptus grandis × E. urophylla. To promote in vitro rooting, the white and yellow spectral qualities caused the best results for the Eucalyptus dunnii and Eucalyptus grandis × E. urophylla, with longer root length and more roots per explant. Eucalyptus dunnii showed reduced adventitious rooting, regardless of spectral quality. Conclusions: Light quality influence the morphophysiological responses of Eucalyptus in different stages of in vitro culture. Our results contribute to maximise the in vitro cloning of important eucalypts species.

The presence of toxic aluminum in the soil and N deficiency are one of the main causes of degradation of cultivated pastures, mainly of the Urochloa genus. The use of agricultural gypsum for restoring soil fertility is one of the ways to recover the productive capacity of degraded areas. Given the above, the work aims to assess pasture recovery with the application of agricultural gypsum associated with nitrogen fertilization. The experimental design was randomized blocks in a 3x4 factorial arrangement, that is, absence of nitrogen, 50 kg ha-1 in the form of ammonium nitrate and 50 kg ha-1 urea, interacting with four doses of agricultural gypsum, namely: 0 ; 750; 1500 and 3000 kg ha-1 and with four replications, totaling 48 plots. The use of urea as a source of N resulted in a higher plant height (PH) when compared to the use of ammonium nitrate, representing a relative increase of approximately 12% in relation to the control. Dose of 1730.8 kg ha-1 of agricultural gypsum resulted in a maximum production of 4.97 t ha-1 of dry pasture. The linear interaction of the use of ammonium nitrate with gypsum doses shows an extremely interesting synergistic potential with this source. For dry mass of culms (CDM), the use of urea had a PMTE of 1730.8 kg ha-1 of agricultural gypsum resulting in 2.38 t ha-1. The culms dry mass of (CDM) represented 47.9% of the total dry mass of the pasture.