Abstract:

In this study, tomato variety of "Golden Crown No.5" was taken as the experiment material.Different radiations (photosynthetically active radiation, PAR < 200 μmol·m^-2·s^-1) and durations (0, 1, 3, 5, 7, 9 d) in the greenhouse by using shading nets and a recovery treatment under normal sunshine conditions were carried out to study the effects of shading stress on flower-fruit, yield formation and fruit quality of greenhouse tomato.The results show that continuous shading stress delays the florescence, reduces the number of flowers and fruits on a single panicle as well as decreases the fruit-setting rate.Shading stress lasting more than 7 days causes the date of tomato flowering delaying about one week.Shading stress also results in the decrease of single fruit weight, yield per plant, fruit diameter and the increase of non-commercial fruit rate.Under the condition of 9-day continuous shading stress, the single fruit weight, yield per plant and fruit diameter are lower than CK (no shading stress) by 0.04 kg, 1.8 kg and 1.1 cm, respectively.The non-commercial fruit rate is higher than CK by 3.1%.Under shading stress, the yield per plant of tomato positively correlates with the photosynthetic parameters such as leaf number, stomatal conductance, transpiration rate and photosynthetic rate significantly, while negatively correlates with intercellular CO₂ concentration.The content of vitamin C, soluble sugar and soluble protein in tomato fruit decrease with the increase of duration of shading stress.In opposite, the ascorbic acid content, organic acid content and total acidity of tomato fruit increase with the longer duration of shading stress.The conclusions from this study can provide a basis for quantitative evaluation of the effects of continuous shading stress on flower-fruit, yield formation and fruit quality of greenhouse tomato.

Key words: Shading stress, Greenhouse, Tomato, Yield, Quality