Comparative study on photosynthetic characteristics of hybrid Lagerstroemia indica ('Red Rocket' ♀ × 'Sichuan Pink Flower' ♂) F1 generation and its parents

To explore the differences in photosynthetic specificity between F1 generation L. indica and its parents, the photosynthetic pigment content and light response curves of 'Red Rocket' (♀), 'Sichuan Pink Flower' (♂) and F1 generation L. indica species were measured under natural growth conditions. The results showed that the relationship between Chl a, Chl b, Car, and Chl content of the L. indica species was as follows: F1 generation > 'Red Rocket' > 'Sichuan Pink Flower'; the size relationship of P_n was: F1 generation > Sichuan Pink F'Sichuan Pink Flower' lower > 'Red Rocket'; the size relationship of G_s was: F1 generation > 'Sichuan Pink Flower' > 'Red Rocket'; LUE was: F1 generation > 'Red Rocket' > 'Sichuan Pink Flower'. When PAR < 1000 μmol·m⁻²·s⁻¹, T_r was as follows: F1 generation > 'Sichuan Pink Flower' > 'Red Rocket'. When PAR > 1200 μmol·m⁻²·s⁻¹, T_r was as follows: 'Red Rocket' > F1 generation > 'Sichuan Pink Flower'; WUE peaks appeared at PAR values of 500~600 μmol·m⁻²·s⁻¹ and 1400~1500 μmol·m⁻²·s⁻¹. Prior to the first peak, WUE of 'Red Rocket' was higher. After the first peak, WUE of 'Sichuan Pink Flower' and F1 generation was higher; F1 generation had the highest P_{n max}, as well as the highest LSP, lowest LCP, and lowest R_d. Therefore, F1 generation of hybrid crape myrtle ('Red Rocket' × 'Sichuan Pink Flower') had the greatest P_{n max} and a wider range of light ecology, which could be in relatively weak light of the forest window and the understory of the sparse forest, and also in the strong light of the roadside and the garden. It is more suitable to 'Red Rocket' on the shady side of the drought-prone backlight, and it is more suitable to plant Sichuan Pink flower the sunny side of the drought-prone area.