The effects of dark treatment on photosynthesis and growth in young and mature leaves of Syzygium rehderianum

Abstract

Light initiates plant photosynthesis, and plant growth depends on light. In order to explore the effects of long-term dark treatment on photosynthesis and leaf growth of plants, this study compared and analyzed the growth state, pigment content, antioxidant capacity, photosynthetic capacity and chlorophyll fluorescence of the leaves of Syzygium rehderianum Merr. and L.M. Perry under full sunlight (natural full sunlight) and a dark treatment. The results showed that the photosynthesis and development of leaves were significantly inhibited after the dark treatment day 3. After the dark treatment day 6, the length and width of the leaves and the synthesis of photosynthetic pigments were significantly lower than those in leaves under full sunlight. Compared with those under full sunlight, the net photosynthetic rate (Pn), maximal quantum yield of PSII photochemistry (Fv/Fm), nonphotochemical quenching and actual photochemical efficiency (Yield) of young and mature leaves were significantly reduced after the dark treatment day 6. These results indicated that the timing of long-term dark treatment caused stress to the leaves. It directly affected the photosynthesis of leaves by affecting the absorption of light energy, inhibiting the synthesis of photosynthetic pigments and destroying the activity of the photosystem II (PSII) reaction center, which ultimately affected the growth and development of plant leaves.