Inhibitory effects of sub-optimal root zone temperature on leaf bioactive components, photosystem II (PS II) and minerals uptake in Trichosanthes cucumerina L. Cucurbitaceae

Abstract

We hypothesized that sub-optimal root zone temperature (RZT) will cause a reduction in the bioactive components contents, adversely affect PS II and hinder uptake/partitioning of mineral elements in the ''Light Green Variant'' of the African snake tomato (Trichosanthes cucumerina L.). Three RZT temperatures (20, 25 and 30°C) were evaluated in a digitally controlled growth chamber. Results showed that for all the mineral nutrients analyzed (Ca, Mg, P, K, Fe and Mn), the amounts absorbed by the plant increase as RZT increases with each nutrient displaying different characteristics with respect to the quantity partitioned into root, stem and leaf at the different RZT. At sub-optimal RZT (20°C), significantly higher amounts of Ca and K were found in the root, whereas at normal RZT (25 and 30°C) higher amounts of Ca were recorded in the stem, and about 50% of the amounts in the stem were found in the leaves. For all the RZT, the amounts of Mg in the leaves were significantly higher than in the root and stem, while the amounts in the stems were also significantly higher than the amounts in the roots. At normal RZT (25 and 30°C) almost equal amounts of P were present in the root, stem and leaf. The amounts of phenolics, ascorbic acid, chlorophyll a and b and total chlorophyll increase as the RZT increases. Photosystem analyses showed that at 30°C the F v /F m (relative photochemical efficiency) was 0.76, while at 20 and 25°C the values were 0.35 and 0.60, respectively. The F v /F m value (0.35) obtained at 20°C confirmed the adverse effects of suboptimal RZT on the photosystem II (PS II). Photosynthetic measurements showed that as the RZT increased, A (net photosynthetic efficiency), E (transpiration rate), C i (intercellular carbon dioxide concentration) and g 1 (stomata conductance) also increased. We postulate that the higher E and g 1 at high RZT have a great physiological implication on plant performance, because transpiration cooling would be improved, especially during the summer; but the lost water must be complemented by adequate irrigation. The totality of the results confirm our hypothesis that sub-optimal RZT will cause a reduction in the bioactive components contents, adversely affect PS II and hinder uptake/partitioning of mineral elements in T. cucumerina.

Ionomic response ofLotus japonicusto different root-zone temperatures

“…These studies also showed that RZT < 20 C, considered sub-optimal for most plants (Zhang et al 2008;Adebooye et al 2010), exacerbates growth as well as nutrient uptake. However, no reports have considered how this important environmental parameter influences the entire network of different elements.…”

“…Indeed, a number of studies have demonstrated that changes in soil temperature can directly affect plant nutrient acquisition by changing root transport properties for nitrogen (N) (BassiriRad et al 1993), phosphorus (P) and potassium (K) (Siddiqi et al 1984;Adebooye et al 2010). …”

Elevated Root-Zone Temperature Modulates Growth and Quality of Hydroponically Grown Carrots

“…Although poorly studied in carrots, root-zone temperature is an important factor for the production of various plant metabolites in many plants [27]- [29]. In African snake tomato (Trichosanthes cucumerina L.), amounts of phenolics, ascorbic acid, and chlorophylls increased with increasing root-zone temperature [27]. In contrast, cucumber seedlings exposed to low root-temperature (12˚C) had significantly higher soluble sugar content than those at 20˚C [28].…”

Effect of Cooling Root-Zone Temperature on Growth, Yield and Nutrient Uptake in Cucumber Grown in Hydroponic System During Summer Season in Cooled Greenhouse

“…While the air temperature is one of the most important environmental elements for the altering secondary metabolism in the plants for production (Kaplan et al, 2004;Zobayed et al, 2005;Ramakrishna & Ravishankar, 2011), the temperature at the root-zone also influences the growth and chemical composition of many plants (Adebooye et al, 2010;Malik et al, 2013;Yan et al, 2013;Sakamoto & Suzuki, 2015a, 2015b. One of the characteristics of hydroponic cultivation is its ability to control the temperature of the nutrient solution around the root system using heaters or cooling spirals, to increase or decrease the temperature, respectively.…”