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.