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Abstract [Objective] The study aims to investigate the effects of drought stress on the photosynthetic characteristics and anatomical structure of turnip (Brassica rapa) leaves, and to provide a basis for the selection and breeding of drought-resistant germplasm and the development of cultivation measures. [Methods] Drought-resistant and drought-sensitive turnip seedlings were selected for normal water-supply and drought-stress potting experiments to analyze the changes in leaf photosynthetic characteristics and anatomical structures. [Results] Drought stress reduced chlorophyll a, chlorophyll b, and total chlorophyll contents, net photosynthetic rate, stomatal conductance, transpiration rate, stomatal limiting values, as well as maximal fluorescence, variable fluorescence, maximal photochemical efficiency, and photochemical potential activity of turnip leaves, while the inter-cellular CO2 concentration, water-use efficiency, and initial fluorescence were increased, with greater variations in drought-sensitive germplasm. Drought also reduced leaf stomatal length, width, openness, density, and tissue laxity, while leaf thickness was increased. Drought also caused swelling of chloroplasts, blurring of basal lamellae, the appearance of cavities, and an increase in osmiophilic and amylopectin granules, while mitochondria were swollen and their internal cristae blurring, while the drought-sensitive germplasm was severely damaged. [Conclusion] Drought stress reduces stomatal opening and tissue structure laxity, increases leaf thickness, impaires the morphological structure of chloroplasts and mitochondria, and reduces the chlorophyll content and photosynthetic efficiency. The drought-resistant germplasm has stronger adaptive regulation to drought stress.

【Background and Objective】 Matrix-culture has been increasingly used in vegetable production, but continuous irrigation and fertilization could result in salinization and degradation of the matrix. The purpose of this paper is to experimentally study the impact of different combinations of irrigation and nitrogen (N) fertilization on water, salt and nitrogen dynamics in sandy matrix of cucumber, as well as its consequence for cucumber yield. 【Method】 The experiment was conducted in a greenhouse and consisted of seven treatments which were designed using the secondary saturated D-optimal design methods. Each treatment had three replicates. All treatments were drip-irrigated. During the experiment, we measured the moisture content, EC, nitrate and ammonium contents at four layers in the matrix after each 20 days, as well as cucumber yield in each treatment. 【Result】 The irrigation amount controlled water movement in the matrix, and the irrigation water moved downwards in most treatments. Mulching the matrix surface with a membrane can suppress the detrimental effect of salt to some extent, but avoiding excessive irrigation and N application is the best way to reduce salt accumulation in the matrix. Water flow took nitrate and ammonium to move with it in the matrix, and there was a threshold for ammonium below which the cucumber roots were unable to take up. The cucumber yield increased with irrigation and nitrogen fertilization parabolically: increasing first and then declining after the irrigation or fertilization exceeded a threshold. 【Conclusion】 On average, in terms of moisture content, the optimal water-nitrogen coupling is to set the upper and low soil moisture content in the matrix for irrigation at 80.20%~89.40% and 60%, respectively, N application at 623~917 kg/hm2. These not only ensure sufficient water and N to the crop, but also reduce the risk of water and N leaching and secondary salinization of the matrix.