Water deficiency causes a dramatic reduction in crop production globally. Breeding crop varieties that are more efficient in their water use is one strategy to overcome this predicament. In this study, a member of the LRR-RLKs family, the Populus nigra × (Populus deltoides × Populus nigra) ERECTA (PdERECTA) gene was cloned. To study the biological functions of PdERECTA, transgenic Arabidopsis plants (35S:PdERECTA) that constitutively expressed the PdERECTA gene were constructed. Overexpression of PdERECTA resulted in early seedling establishment, longer primary roots, and larger leaf areas. Notably, transgenic Arabidopsis overexpressing PdERECTA resulted in enhanced long-term water use efficiency (WUEl), as estimated by the analysis of carbon isotopic discrimination. The WUEl results were supported by the physiological and anatomical results, which included improved photosynthetic rate, decreased transpiration rate, and stomatal density. The transgenic lines have significantly more dry-biomass as compared to the wild type. Since the overexpression of PdERECTA can strongly enhance the water use efficiency in transgenic Arabidopsis plants, PdERECTA could potentially be used in transgenic breeding to improve the water use efficiency.

In this study, we prepared polyethyleneimine (PEI) and graphene oxide (GO) composite adsorbent PEI-GO through an amidation reaction between the amine groups of the PEI and the carboxyl groups of the GO. Adsorption performance of the PEI-GO was tested by removing Cr(VI) ions from an aqueous solution. The physico-chemical properties of the GO, pristine and Cr(VI) ions loaded PEI-GO were investigated by the FT-IR, SEM-EDX and XPS methods. To investigate the adsorption kinetics of Cr(VI) ions onto this newly developed PEI-GO, we performed a batch of experiments under different adsorption conditions: content of the PEI in the PEI-GO, solution pH, initial Cr(VI) ion concentration, adsorption temperature and contact time. The prepared PEI-GO exhibited an encouraging uptake capacity of 539.53 mg/g. The adsorption process was fast, within the first 1 h, Cr(VI) ion adsorption onto the PEI-GO was about 71 %, and the adsorption equilibrium could be obtained within 14 h. Kinetics experiments indicated that the adsorption process could TP * P T 2 be described by the pseudo-second-order kinetic model. Furthermore, our adsorption equilibrium data fit the Langmuir isotherms well (R 2 >0.99). The removal mechanism of Cr(VI) ions from the solution consists of two steps: (1) Cr(VI) ions binds to the 4PEI-GO by the electrostatic interaction between the negatively charged Cr(VI) ions species and the protonated amine groups of the 4PEI-GO; and (2) small part of Cr(VI) ions were reduced to Cr(III) ions with the assistance of π electrons on the carbocyclic six-membered ring of the 4PEI-GO and then bind on the 4PEI-GO by the electrostatic attraction between Cr(III) ions and negatively charged groups (COO − ) of the 4PEI-GO. Based on the results obtained in this work, it can be concluded that the prepared PEI-GO can be an effective and potential adsorbent for removing Cr(VI) ions from an aqueous solution.

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