Morphological and Photosynthetic Response to High and Low Irradiance of Aeschynanthus longicaulis

Aeschynanthus longicaulis plants are understory plants in the forest, adapting to low light conditions in their native habitats. To observe the effects of the high irradiance on growth and physiology, plants were grown under two different light levels, PPFD 650 𝜇mol⋅m–2 ⋅s–1 and 150 𝜇mol⋅m–2 ⋅s–1 for 6 months. Plants under high irradiance had significantly thicker leaves with smaller leaf area, length, width, and perimeter compared to the plants grown under low irradiance. Under high irradiance, the leaf color turned yellowish and the total chlorophyll decreased from 5.081mg⋅dm−2 to 3.367mg⋅dm−2. The anthocyanin content of high irradiance leaves was double that of those under low irradiance. The plants under high irradiance had significantly lower A𝑚𝑎𝑥 (5.69 𝜇mol⋅m–2 ⋅s–1) and LSP (367 𝜇mol⋅m–2 ⋅s–1) and higher LCP (21.9 𝜇mol⋅m–2 ⋅s–1).Thechlorophyll fluorescence parameter 𝐹V/𝐹𝑚 was significantly lower and NPQ was significantly higher in high irradiance plants. RLCs showed significantly lower ETRmax and 𝐸𝑘 in plants under high irradiance. It can be concluded that the maximum PPFD of 650 𝜇mol⋅m–2 ⋅s–1 led to significant light stress and photoinhibition of A. longicaulis.