High irradiance promotes decreases in the quantum yield in plants, which reduce the photosynthetic rate. The excess of light in combination with water deficit can intensify the response of plants to stress, especially in species susceptible to those factors. The aim of the present study was to characterize the photosynthetic activity of young jatobá-do-cerrado (Hymenaea stigonocarpa Mart. ex Hayne) trees under different irradiance conditions, both alone and/or in combination with water deficit. Four irradiances [45, 230, 510, and 1,700 μmol(photon) m -2 s -1 ] and two levels of water in soil (90% and 50% of field capacity) were used. Gas exchange, water potential, and chlorophyll a fluorescence were measured. The highest rates of photosynthesis were observed under irradiances of 230 and 510 μmol(photon) m -2 s -1 . Irradiance of 1,700 μmol(photon) m -2 s -1 led to the photoinhibition of photosynthesis, as indicated by a reduced maximum quantum yield of PSII, effective quantum yield ratio, and electron transport rate, as well as higher nonphotochemical quenching. The most stressful to young H. stigonocarpa plants was high irradiance, while water deficit did not intensify the response to light stress.

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Sclerotinia sclerotiorum is a necrotrophic parasitic fungus that causes Sclerotinia stem rot (SSR), which is currently one of the most difficult agronomic crop diseases to control. A number of plants of the Brazilian Cerrado biome have been shown to be important sources of symbiotic microorganisms with biotechnological potential, so we decided to test the potential of bacteria isolated from the dwarf jelly palm, Butia archeri (Arecaceae) for the control of the pathogenic effects provoked by S. sclerotiorum. For this, we bioprimed seeds and evaluated the effects of this biopriming on the OJIP transient patterns prior to and following infection by the phytopathogen. Plants treated with the BA48R strain of Enterobacter sp., and in particular, those treated with the BA88R strain of Bacillus cereus presented the best results in terms of the loss/gain of the physiological and symptomatological variables evaluated. The plants bioprimed with BA88R presented high post-infection levels of total chlorophyll (33.35 FCIs) and chlorophyll a (26.39 FCIs), maintained a high Nitrogen Balance Index (NBI = 18.87), and synthesized low concentrations of flavonoids (1.39). These plants also maintained high levels of PIABS (1.111) and PITOTAL (1.300) following infection, and low levels of Di0/RC (0.602), which indicates that, in the presence S. sclerotiorum, the efficiency of the photosynthesis in the plants treated with these bacteria was less affected in the reaction centers, as confirmed by the negative amplitude recorded in the L band. The present study reconfirms the importance of the use of chlorophyll fluorescence for the diagnosis of disease and conditions of stress in crop plants, in addition to demonstrating the effectivenesss of the BA48R bacterial strain and, in particular, the BA88R strain on systemic resistance induction and suppression of S. sclerotiorum in Glycine max plants, with enormous potential for the development of more sustainable agricultural processes.

Brosimum gaudichaudii is a plant species with medicinal relevance due to its furanocoumarin accumulation. The accumulation of these compounds in the root promotes predatory extractivism, which threatens the conservation of the species. In addition, little is known about the conditions for culturing of this species in vitro. The present study aimed to investigate how the application of different spectra of LEDs (white, blue, red, and combinations of blue and red at 1:1 and 3:1 ratios) can impact the morphophysiological and biochemical characteristics of B. gaudichaudii under different in vitro conditions. To evaluate the production of furanocoumarins in its leaves, which are easy-to-collect perennial organs, we cultured nodal segments in 50-mL tubes with MS medium under 100 μmol m−2 s−1 light and a photoperiod of 16 h for 50 days. We then submitted the seedlings biometric, anatomical, biochemical, and physiological evaluations. The different spectral qualities influenced several characteristics of the seedlings. Plants grown under red light showed greater stem elongation and larger and thinner leaves, strategies aimed at capturing a higher ratio of radiant energy. Exposure to the blue/red ratio of 1:1 induced increases in the concentration of the furanocoumarin psoralen, probably due to the diversion of carbon from primary metabolism, which resulted in lower growth. Cultivation under blue light or blue:red light at 3:1 triggered anatomical and physiological changes that led to higher production of secondary metabolites in the leaves, and at the 3:1 ratio, the seedlings also had a high growth rate. These results highlight the fundamental role of light in stimulating the production of secondary metabolites, which has important implications for the production of compounds of interest and indirect consequences for the conservation of B. gaudichaudii.

Anacardium othonianum Rizz., popularly known as the Cerrado cashew tree, is widely used in medicine due to its therapeutic properties, including its antioxidant, anti-inflammatory, and antidiarrheal activities. Light is an important regulator of the growth, development of plants differentiation, and metabolism. Considering the influence of light on the production of phytochemicals, the aim of the present study was to evaluate production of gallic and 3,4-dihydroxybenzoic acids and amentoflavone in A. othonianum seedlings grown in vitro exposure to white, blue, green, red, and yellow light. The seedlings were evaluated with respect to the length of the aerial parts and the number of leaves, at 0, 20, and 40 days of treatment. The fresh and dry weights of the aerial parts and the levels of phenolic acid and biflavonoid were evaluated at 40 days via high-performance liquid chromatography with a diode array detector (HPLC-DAD). Regardless of the light wavelength used for the growth, the largest length of the aerial parts (5.54 cm) and an increase in the number of leaves (2.86-fold) were observed at 40 days. The largest accumulations of fresh weight (325.5 mg and 335.1 mg per seedling) and dry weight (83.3 mg and 84.5 mg per seedling) were observed in seedlings grown under red and yellow light, respectively. Relatively higher levels of gallic acid (0.66 mg.g -1 dry weight) and amentoflavone (1.41 mg.g -1 dry weight) were found in seedlings grown under blue light. In contrast, the 3,4-dihydroxybenzoic acid levels of the seedlings under red light increased (8.22 mg.g -1 dry weight).