Coupling physiological analysis with proteomic profile to understand the photosynthetic responses of young Euterpe oleracea palms to drought.

This study examined whether drought sensitivity in açaí (Euterpe oleracea Mart.) is associated with reductions in photosynthesis and increasing oxidative stress in response to down-regulation of proteins related to photosynthetic reactions, photorespiration, and antioxidant system. Well-watered (Control) and drought-stressed plants were compared when leaf water potential in stressed plants reached around - 1.5 and - 3.0 MPa, representing moderate and severe drought. Drought caused 84 and 96% decreases in net photosynthetic rate (Pn) and stomatal conductance. Stress-mediated changes in maximum quantum efficiency of photosystem II (PSII) photochemistry were unobserved, but drought decreased photochemical quenching, actual quantum yield of PSII electron transport, and apparent electron transport rate (ETR). Moderate and severe drought induced, respectively, decreases and increases in non-photochemical quenching (NPQ) and 74 and 273% increases in ETR/Pn. Moderate drought down-regulated PSII protein D2, chlorophyll a-b binding protein 8, photosystem I reaction center subunit N, sedoheptulose-1,7-bisphosphatase, and transketolase; while severe drought down-regulated LHC II proteins, ferredoxin-NADP reductase, ATP synthase subunits ε and ß, and carbonic anhydrase isoform X2. The glutamate-glyoxylate aminotransferase 2 and glycine dehydrogenase were down-regulated upon moderate drought, while catalase 2 and glycine cleavage system H protein 3 were up-regulated. Severe drought up-regulated glycolate oxidase, glycine cleavage system H protein 3, and aminomethyl transferase, but most of photorespiration-related proteins were only found in control plants. Down-regulation of chaperones and antioxidant enzymes and increased lipid peroxidation in stressed plants were observed upon both stress severities. Therefore, the decreases in Pn and failure in preventing oxidative damages through adjustments in NPQ and photorespiration- and antioxidant-related proteins accounted for drought sensitivity in açaí.

Bioagents and silicon promoting fast early upland rice growth.

Upland rice can overcome major challenges through the insertion of silicate fertilization and the presence of plant growth-promoting microorganisms (PGPMs) during its cultivation, as these factors promote an increase in vigor and plant disease resistance. Two consecutive experiments were conducted to evaluate the beneficial effects of silicon fertilization combined with the PGPM, Pseudomonas fluorensces, Burkholderia pyrrocinia, and a pool of Trichoderma asperellum, in upland rice seedlings, cultivar BRS Primavera CL: (a) E1, selecting PGPM type and Si doses for rice growth promotion and leaf blast supression, and (b) E2, evaluating physiological characteristics correlated with mechanisms involved in the higher vegetative growth in highlighted treatments from E1. In E1, 2 Si t ha-1 combined with the application of T. asperellum pool or PGPM mixture increased 54% in root dry matter biomass and 35 and 65% in shoot and root lengths, respectively; it also suppressed 99% of rice blast severity. In E2, shoot and root dry matter biomass and length, photosynthetic rate, water use efficiency, total soluble sugar, and chloroplastidic pigments were superior in BRS Primavera CL seedlings treated with 2 Si t ha-1 and T. asperellum pool or PGPM mixture. Higher salicilic and jasmonic acid levels were found in seedlings treated with Si and T. asperellum pool, individually. These physiological characteristics may explain, in part, the higher vigor of upland rice seedlings promoted by the synergistic effect between silicate fertilization and beneficial microorganisms.