Effects of supplemental lighting duration and matrix moisture on net photosynthetic rate of tomato plants under solar greenhouse in winter

Supplemental lighting (SL) ensures the yield and quality of greenhouse crops in winter, and the proper SL duration facilitates the balance between plant demand and energy consumption. Furthermore, irrigation management affects tomato quality and quantity. To reveal the effects of SL duration and relative matrix moisture on tomato photosynthesis and phenotype, two factors randomized block design was used, in which the SL duration was 9:00 to 10:00 (L1), 8:00 to 11:00 (L2), 7:00 to 12:00 (L3) and no SL (L4), and the relative matrix moisture was 20% to 35% (M1), 40% to 55% (M2) and 60% to 75% (M3). The photosynthetic and environmental parameters were measured by a portable photosynthesis system and wireless sensor networks (WSN), respectively. In addition, phenotypic parameters were used to assist in the difference analysis. The results showed that the improvement of the net photosynthetic rate (Pn) brought by SL from 9:00 to 10:00 was the highest while 11:00 to 12:00 was the worst in the morning, and the Pn was the highest in L3M3 at the end of the fruiting stage, followed by L3M2. At low moisture, the Pn was the highest in L2M1. The SL duration should avoid the photosynthetic midday depression, and the SL should be coordinated with sufficient irrigation to avoid potential water stress.