Synergistic effects of temperature, CO₂ concentration and irrigation amount on the growth, yield and quality of cherry tomato under delayed autumn cultivation in greenhouse

Objectives In order to cope with theincreasing trend of environmental temperature and CO₂ concentration, we studied the effects of different irrigation amounts on the growth, yield, and quality of cherry tomatoes, as well as the key growth and photosynthetic factors related to the final yield and quality of fruits.

Methods Using ‘Fenmei 1’ cherry tomato as the research subject, a three-factor randomized block experiment was conducted with two temperatures levels (T₁: ambient temperature, and T₂: ambient temperature + 2.3℃), two CO₂ concentration levels (C₁: 400 μmol/mol, and C₂: 800 μmol/mol), and three irrigation amounts (I₁: 75% Ep, I₂: 100% Ep, and I₃: 125% Ep). Here, Ep represents the cumulative evaporation capacity (mm) of a standard evaporating dish with a diameter of 20 cm, resulting in a total of 12 treatments. Sixteen indicators across five categories of growth, photosynthesis, yield, quality and irrigation water use efficiency of cherry tomato were determined. The regulatory effects of single-factor and multi-factor interaction on different indicators were analyzed. The key indicators related to yield and quality were extracted using correlation analysis and path analysis.

Results I₁ treatments exhibited lower net photosynthetic rate (Pn) and total chlorophyll content during whole growing period. I₃ irrigation level promoted plant height and leaf area under T₂C₂ combination from flowering-fruit setting stage to fruiting stage, with the leaf dry matter accumulation of T₂C₂I₃ at fruiting stage was 47.5% higher than the value in T₂C₂I₁ at the same period. I₂ irrigation level promoted the accumulation of stem dry matter under T₂, with the stem dry matter mass in T₂C₂I₂ treatment at the fruiting stage being 33.3% higher than that in T₂C₂I₁ treatment during the same period. I₂ enhanced root growth across various environments, and T₁C₂I₂ was recorded the maximum root dry matter accumulation, exceeding the minimum observed in T₂C₁I₁ by 106.8% at the fruiting stage. Temperature and irrigation significantly affected all quality indexes. Under the T₂C₁I₁ combination, the contents of total soluble solids, acidity, soluble protein, total soluble sugar and vitamin C were the highest, with its total soluble sugar content being 61.1% higher than that of the T₁C₁I₃ combination. T₁C₂I₃ achieved the highest yield, which was 124.8% higher than that of the T₂C₁I₁ treatment. Moreover, the I₂ irrigation level enhanced irrigation water use efficiency under the T₂ and C₁ environmental conditions. Path analysis indicated that the net photosynthetic rate at seedling stage had the greatest contribution to yield among the net photosynthetic rates at different growth stages, with a path coefficient of 0.539. Stem dry matter accumulation during the flowering-fruit setting stage and fruiting stage had the greatest contributions to lycopene and total soluble sugar content, with direct path coefficients of −0.695 and −0.660, respectively.

Conclusions Elevated temperature is detrimental to plant growth and dry matter accumulation from the seedling stage to the flowering-fruit setting stage of tomato, and it is also unfavorable for yield formation. However, elevated temperature combined with mild drought could enhance the resistance and fruit quality of tomatoes. Under the future environmental trends of rising temperature and CO₂ concentration, increasing the irrigation levels is a necessary means to fully utilize environmental factors and enhance the benefits of greenhouse-cultivated crops.