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Zhixiong Zeng, Jiaming Guo, Xinyu Wei, Enli Lü and Yanhua Liu

Mechanical ventilation systems are applied in greenhouses for temperature adjustment, but they consume a large amount of energy. This research aims to optimize the energy consumption of a variable air volume (VAV) fan-pad evaporative cooling system via experimentation. We discuss the effects of adjusting the VAV fan-pad evaporative cooling system on temperature and humidity, and we provide an estimate of the corresponding energy consumption under different highest stable temperature conditions. The test results demonstrate that a higher fan frequency is typically accompanied by greater ventilation quantity, faster cooling speed, more pronounced effects of the fan-pad evaporative cooling system fan, and more intensive energy consumption during the cooling process compared with a low fan frequency. When the temperature increased for 71 seconds or 60 seconds in a specific temperature zone (34 to 35 °C), the indoor temperature could be reduced to the optimum for crops with a fan frequency of 20 Hz, saving more than 87% of the energy output. When the warm-up time for a specific temperature zone (34 to 35 °C) was 41 seconds, the indoor temperature could be reduced to the optimum temperature for crops only when the fan frequency was 50 Hz. The VAV fan-pad evaporative cooling system increased the relative humidity in the greenhouse to satisfy crop production demands. The temperature of crops shared the same variation trend as temperatures inside the greenhouse. Our research results theoretically benefit cooling control and energy-saving design of greenhouses in the subtropics.

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Mengyang Liu, Yin Lu, Shan Wang, Fang Wu, Jingrui Li, Yanhua Wang, Jianjun Zhao and Shuxing Shen

Leaf color mutants play an important role in our understanding of chlorophyll biosynthesis and catabolism. In this study, we obtained a yellow-green leaf mutant hy in an ethyl methanesulfonate mutagenized population of chinese cabbage (Brassica rapa ssp. pekinensis). The hy phenotype was controlled by a recessive allele at a single locus. The intrinsic photochemical activity of photosystem II (PSII) is impaired in hy, suggesting that absorbed light energy is not efficiently transferred from the light-harvesting complexes antenna to the PSII reaction centers and dissipated as heat or fluorescence. We measured chlorophyll content and chlorophyll precursors and analyzed the expression of key genes in the chlorophyll synthetic pathway in hy and wild type. The mutation phenotype was consistent with inhibited expression of chlorophyll a oxygenase (CAO) gene in the chlorophyll synthetic pathway. In mutant hy, CAO cDNA was cloned so that a C to T mutation at 1099 bp caused a conserved proline (Pro) to serine (Ser) mutation at the 367th amino acid in C-domain, which changed the secondary structure of CAO protein. We speculate that the mutation amino acid changed in the C-domain may affect the catalytic function in mutant CAO.