Exploring adequate CO₂ elevation for optimum tomato growth and yield under protected cultivation

The adequate elevation of CO₂ concentrations (e [CO₂]) could not be assessed by constrained analysis of comparative experimental study for optimum plant growth and yield with improved fruit quality owing to the lack of conjunctive investigation of plant parametric responses. Instead, the principal component analysis (PCA) and technique for order preference by similarity to ideal solution (TOPSIS) assessed and quantified the parametric plant responses to identify the adequate level of e [CO₂] for optimum plant growth and yield. In this study, tomato plants were grown under an ambient CO₂ (a [CO₂], 500 μmol mol^-1) and three e [CO₂] (700, 850 and 1000 μmol mol^-1): named EC₇₀₀, EC₈₅₀ and EC₁₀₀₀, respectively, in autumn-winter (AW) 2020 and spring summer (SS) 2021 growing seasons to investigate and evaluate the plant parametric responses under e [CO₂]. The tomato plant's response with maximum transportability of biomass to fruits was observed under 700 μmol mol^-1. The plant height, stem diameter and LAI were enhanced compared to a [CO₂] at the optimum level under 1000 μmol mol^-1 (by 50.53, 20.98 and 44.44%) and 700 μmol mol^-1 (by 22.41, 12.09 and 26.88%) in Aw 2020; Ss 2021, respectively. The optimum yield was increased under 700 μmol mol^-1 by 73.95% and 55.58% in Aw 2020; Ss 2021, respectively. EC₇₀₀ was ranked as a priority by TOPSIS with 0.632 and 0.694 plant response performance index in Aw 2020; Ss 2021, respectively, to get optimum tomato growth, yield, water use efficiency and fruit quality. The results of this study are beneficial for commercial greenhouse crop production by fumigating the adequate level of e [CO₂], to reduce the cost of CO₂ fertigation, enhance the yield and save the water quantity.