Biology subjects

Machado, E. C.

Publications and source records attributed to Machado, E. C..

3 recordsLinked to original sources

bioRxiv2023

Xylem sap residue in cut-open conduits can affect gas discharge in pneumatic experiments

O_LIConsiderable progress has been made in understanding the mechanisms of embolism formation based on the pneumatic method, which relies on gas discharge measurements. Here, we test the assumption that cut-open conduits are gas-filled when samples are cut at high water potentials. C_LIO_LIWe performed vulnerability curves (VC) with the Pneumatron and analysed sap extraction from cut-open vessels in Citrus branches, while the optical method was applied as a reference method. VCs of 11 additional angiosperms were analysed to generalise our findings. C_LIO_LIWe found an increase in gas discharge during early stages of dehydration, which affected the VC of Citrus. Xylem sap was not absorbed immediately by surrounding tissue in cut Citrus branches. The gas amount discharged increased until all sap residue was absorbed, which was near the turgor loss point. By analysing the slope of VCs, we could correct pneumatic VC, as evidenced by the strong agreement in embolism resistance between the pneumatic and the optical method. C_LIO_LISince residual sap in cut-open conduits of some species could slightly reduce embolism resistance in some species, we propose to apply an easy correction for this novel artefact. Automated measurements with a Pneumatron are also required because of its high time resolution. C_LI

plant biology↗

bioRxiv2022

Dynamic changes in gas solubility of xylem sap reiterate the enigma of plant water transport under negative pressure

Despite a long research history, we do not fully understand why plants are able to transport xylem sap under negative pressure without constant failure. Microbubble formation via direct gas entry is assumed to cause hydraulic failure, while the concentration of gas dissolved in xylem sap is traditionally supposed to be constant, following Henrys law. Here, the concentration of soluble gas in xylem sap was estimated in vivo using well-watered Citrus plants under varying levels of air temperature and photoperiodic exposure, and compared to modelled data. The gas concentration in xylem sap showed non-equilibrium curves, with a minimum over- or undersaturation of 5% compared to gas solubility based on Henrys law. A similar diurnal pattern was obtained from the gas concentration in the cut-open conduits and discharge tube, and oversolubility was strongly associated with decreasing xylem water potentials during transpiration. Although our model did not explain the daily changes in gas solubility for an anisobaric situation, oversolubility characterises nanoconfined liquids, such as sap inside cell walls. Thus, plants are able to transport sap under negative pressure with relatively high amounts of dissolved gas, providing them with a buffering capacity to prevent hydraulic failure, despite diurnal changes in pressure and temperature.

plant biology↗

bioRxiv2019

Enhanced nitric oxide synthesis through nitrate supply improves drought tolerance of sugarcane plants

Nitric oxide (NO) is an important signaling molecule associated with many biochemical and physiological processes in plants under stressful conditions. Nitrate reductase (NR) not only mediates the reduction of NO3- to NO2- but also reduces NO2- to NO, a relevant pathway for NO production in higher plants. Herein, we hypothesized that sugarcane plants supplied with more NO3- as a source of N would produce more NO under water deficit. Such NO would reduce oxidative damage and favor photosynthetic metabolism and growth under water limiting conditions. Sugarcane plants were grown in nutrient solution and received the same amount of nitrogen, with varying nitrate:ammonium ratios (100:0 and 70:30). Plants were then grown under well-watered or water deficit conditions, in which the osmotic potential of nutrient solution was -0.15 and -0.75 MPa, respectively. Under water deficit, plants exhibited higher root [NO3-] and [NO2-] when supplied with 100% NO3-. Accordingly, the same plants also showed higher root NR activity and root NO production. We also found higher photosynthetic rates and stomatal conductance in plants supplied with more NO3-, which improved root growth. ROS accumulation was reduced due to increases in the activity of catalase in leaves and superoxide dismutase and ascorbate peroxidase in roots of plants supplied with 100% NO3- and facing water deficit. Such positive responses to water deficit were offset when a NO scavenger was supplied to the plants, thus confirming that increases in leaf gas exchange and plant growth were induced by NO. Concluding, NO3- supply is an interesting strategy for alleviating the negative effects of water deficit on sugarcane plants, increasing drought tolerance through enhanced NO production. Our data also provide insights on how plant nutrition could improve crop tolerance against abiotic stresses, such as drought. HighlightsO_LINitrate supply improves sugarcane growth under water deficit. C_LIO_LINitrate supply stimulated nitrate reductase activity and NO synthesis in sugarcane roots facing water deficit. C_LIO_LILeaf gas exchange was increased by nitrate supply as well as root growth under water limiting conditions. C_LIO_LIAntioxidant responses were also improved in plants supplied exclusively with nitrate. C_LIO_LINitrogen management may be an interesting strategy for improving drought tolerance in sugarcane fields. C_LI

plant biology↗