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【Objective】 Photosystem II (water-plastoquinone oxidoreductase) is a protein complex in light-dependent reactions of oxygenic photosynthesis. The purpose of this paper is to study the effect of salt stress on photosystem II of rice seedlings. 【Method】 We used the varieties of Changbai 9 and Baijing 1 as the model plants. The salt was a mixture of salts at ratios of NaCl∶Na2SO4∶Na2CO3∶NaHCO3=1∶9∶1∶9. Solution of this salt mixture at concentrations from 0 to 120 mmol/L was added to the soil with the irrigation water. In each treatment, we measured and calculated the rapid chlorophyll fluorescence induction kinetic curve using the JIP-test, from which we calculated the the change in photosystem II in the leaves of the rice seedlings. 【Result】 When salt concentration was in 0~80 mmol/L, the chlorophyll fluorescence kinetic curve of the rice seedlings of both varieties was a typical OJIP curve, and the fluorescence intensity in each treatments differed significantly from the Point J. When salt concentration was increased to 120 mmol/L, the OJIP curve of the two varieties flattened, changing from the Point J to Point P, with the fluorescence intensity at Point I and Point P decreasing remarkably compared to CK (without salinity). There were non-linear relationships between salt concentration and the index PIABS, (φEo, φRo, ψEo), donor-side index (WK) and the recipient-side index (VJ) for both varieties. With the increase in soil salinity, water content, the contents of chlorophyll a and b, maximum photochemical efficiency (FV/FM), quantum yield and efficiency (φEo, φRo, ψEo), the index PIABS of both varieties all gradually decreased, while WK, VJ, and the heat dissipation ratio (φDo) gradually increased. The change in water content, chlorophyll content and chlorophyll fluorescence parameters of the two varieties gradually increased with the increase in salt concentration. 【Conclusion】 Saline-alkali stress severely damages the donor/acceptor laterality, especially the acceptor lateral performance index VJ, hindering electron transmission and reducing the quantum yield and the performance of photosystem II. PSII performance index PIABS, VJ, WK and quantum yield are nonlinearly correlated with the salt concentration.

Object detection in aerial images has had a broader range of applications in the past few years. Unlike the targets in the images of horizontal shooting, targets in aerial photos generally have arbitrary orientation, multi-scale, and a high aspect ratio. Existing methods often employ a classification backbone network to extract translation-equivariant features (TEFs) and utilize many predefined anchors to handle objects with diverse appearance variations. However, they encounter misalignment at three levels, spatial, feature, and task, during different detection stages. In this study, we propose a model called the Staged Adaptive Alignment Detector (SAADet) to solve these challenges. This method utilizes a Spatial Selection Adaptive Network (SSANet) to achieve spatial alignment of the convolution receptive field to the scale of the object by using a convolution sequence with an increasing dilation rate to capture the spatial context information of different ranges and evaluating this information through model dynamic weighting. After correcting the preset horizontal anchor to an oriented anchor, feature alignment is achieved through the alignment convolution guided by oriented anchor to align the backbone features with the object's orientation. The decoupling of features using the Active Rotating Filter is performed to mitigate inconsistencies due to the sharing of backbone features in regression and classification tasks to accomplish task alignment. The experimental results show that SAADet achieves equilibrium in speed and accuracy on two aerial image datasets, HRSC2016 and UCAS-AOD. [ABSTRACT FROM AUTHOR]

Combined elemental deficiencies are more complex and insidious physiological metabolic responses than single elemental stresses. To determine the effects of phosphorus (P), iron (Fe), zinc (Zn), and their deficient combinations on photosynthetic characteristics of rice seedlings, we investigated their effects on dry weight, chlorophyll (Chl) content, rapid photosynthetic carbon assimilation CO2 responses, and Chl fluorescence in four-week-old rice (CB9 and BJ1 cultivars) seedlings. The results showed that the dry matter, maximum carboxylation efficiency (Vc,max), and maximum electron transfer efficiency (Jmax) of seedlings were all reduced to different degrees under the element deficiency treatments. JIP-test analysis showed that the decrease in the concentration of active PSII reaction centers (RC/ABS) under -Zn treatment was the main reason for the inhibition of performance index PIABS. The -P treatment reduced RC/ABS and inhibited electron transfer (ψEo). Primary photochemical reactions (φPo) of -P-Zn treated seedlings were also inhibited compared to the -P treatment. The -Fe and -Fe-Zn treatments inhibited photosynthesis most severely, which not only reduced RC/ABS but also severely inhibited φPo and ψEo. Notably, the -P-Fe and -P-Fe-Zn treatments of the CB9 improved the RC/ABS, alleviating the limitation of Fe deficiency. These results help enhance the understanding of the complex relationship between nutrient balance and photosynthesis, especially for P, Fe, Zn, and their combined deficiency. [ABSTRACT FROM AUTHOR]