The Photosynthetic Characteristics of Leaves in Different-Colored Brassica juncea.

Leaf color is a key trait influencing photosynthetic efficiency in plants. This study investigates the photosynthetic characteristics of differently colored leaves in Brassica juncea L. using green-leaved (SWJ) and purple-red-leaved (RLJ) varieties, their reciprocal F1 hybrids, and F2 populations. The results show that the net photosynthetic rate and chlorophyll content of SWJ were significantly higher than those of RLJ, while F1 hybrids exhibited intermediate photosynthetic performance. All five measured photosynthetic traits-net photosynthetic rate, stomatal conductance, intercellular CO2 concentration, transpiration rate, and chlorophyll content-segregated significantly in the F2 generation and were identified as quantitative traits. Notably, transpiration rate was positively correlated with leaf color, whereas no correlation was found with net photosynthetic rate or intercellular CO2 concentration. A key finding is the occurrence of purple-leaved plants with high photosynthetic rates and green-leaved plants with low photosynthetic rates in the F2 generation, indicating the potential to combine high photosynthesis with anthocyanin-rich purple leaves. This study provides new genetic insights and a theoretical basis for breeding high-yield, stress-tolerant Brassica juncea varieties.