4. In some higher plants, the C4 photosynthetic pathway has evolved, exhibiting higher photosynthetic efficiency under specific environmental condions compared to plants solely possessing the C3 pathway. Please elaborate on:(A) The key biochemical steps of the C4 photosynthetic pathway and its spatialialialialialali separation in cells. (B) How the C4 pathway overcomes the limitation imposed by photorespiration onl photosynthetic rate in the C3 pathway. (C) In which typical ecological environments do have a greater competitive advantage, and explain their physiological basis. (15 point)

7. Please briefly explain the meaning of the following abstract and describe what your next step would be if you were the author?"Aluminum (Al) toxicity in acid soils poses a sicant threat to rice, which exhibits highly complex genetic mechanisms for both extemal detoxification and internal tolerance among cereal crops. several genes involved Al tolerance have been identified, the molecular mechar underlying Al tolerance in rice remain to be fully explored. Here, we functionally characterized the gibberellin-stimulated transcription gene OsGASRI, which encodes a small cysteine-rich peptide localized to the nucleus and cytoplasm and plays a significant role in AI tolerance in rice. The expression ASR1 is rapidly up-regulated by Al in rice root tips but not in the shoots. Its expression requlated by the central regulator Aluminum Resistance Transcription Factor 1 (ART), indicating that OsGASR1 functions as a novel gene in rice Al resistance independent of ART1. Knockout of OsGASR1 reduced root length but did not affect Al tolerance in rice, whereas overexpression of OsGASR1 enhanced tolerance without affecting Al distribution and accumulation and promoted the accu reactive oxygen species (ROS) in the root tips. RNA-seg analysis revealed that overexpression of OsGASR1 uprequlated the expression of genes associated with cell wall modification, oxidative stress, AI tolerance. Collectively, these findings suggest that OsGASR1 is involved in Al tole dently of ART1, and the up-regulation of this gene is necessary for rice Al tolerance. i. 2025 Jan:350:112294. doi: 10.1016/j plantsci.2024.112294. Epub 2024 Oct 15.)

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