Yield, Physiological Performance, and Phytochemistry of Basil (Ocimum basilicum L.) under Temperature Stress and Elevated CO2 Concentrations

Abstract

Early season sowing is one of the methods for avoiding yield loss for basil due to high temperatures. However, basil could be exposed to sub-optimal temperatures by planting it earlier in the season. Thus, an experiment was conducted that examines how temperature changes and carbon dioxide (CO2) levels affect basil growth, development, and phytonutrient concentrations in a controlled environment. The experiment simulated temperature stress, low (20/12 °C), and high (38/30 °C), under ambient (420 ppm) and elevated (720 ppm) CO2 concentrations. Low-temperature stress prompted the rapid closure of stomata resulting in a 21% decline in net photosynthesis. Chlorophylls and carotenoids decreased when elevated CO2 interacted with low-temperature stress. Basil exhibited an increase in stomatal conductance, intercellular CO2 concentration, apparent quantum yield, maximum photosystem II efficiency, and maximum net photosynthesis rate when subjected to high-temperature stress. Under elevated CO2, increasing the growth temperature from 30/22 °C to 38/30 °C markedly increased the antioxidants content of basil. Taken together, the evidence from this research recommends that varying the growth temperature of basil plants can significantly affect the growth and development rates compared to increasing the CO2 concentrations, which mitigates the adverse effects of temperature stress.

The Effect of Antagonist Abiotic Stress on Bioactive Compounds from Basil (Ocimum basilicum)

“…The phenylpropanoid pathway is usually activated under stressful conditions (drought, flooding, temperature changes), leading to modifications in the composition of plant extracts [19]. The response of basil plants to abiotic stress has been extensively studied [6,[28][29][30][31][32][33]; however, the physiological and biochemical response to antagonist drought−flooding stress on basil plants has not been reviewed.…”

Drought and Elevated CO2 Impacts Photosynthesis and Biochemicals of Basil (Ocimum basilicum L.)

“…An LI-6400XT portable photosynthesis system (LiCor Biosciences, Inc., Lincoln, NE, USA) was used to measure photosynthesis and fluorescence parameters on the same leaf between 1000 and 1200 h at 18 DAT. The setup and regulation of relative humidity, the temperature of the chamber, and light intensity in the leaf chamber were followed as described by Barickman et al [96]. Net photosynthesis (Pn) and quantum efficiency (Fv'/Fm') were measured when the total coefficient of variation (percent CV) was less than 0.5 percent.…”

“…Lipid peroxidation of membranes was estimated from MDA content, a final lipid peroxidation product, using the method described by Heath and Packer [99] with few modifications as described by Barickman et al [96]. The extinction coefficient of 155 mM −1 cm −1 was used to determine the MDA concentration, which was reported as nmol g −1 DW.…”

“…The content of H 2 O 2 was measured following the method of Mukherjee and Choudhuri [100] with few modifications as described by Barickman et al [96]. The content of H 2 O 2 in samples was obtained from a standard curve using pure H 2 O 2 and expressed as µmol g −1 DW.…”

“…Trehalose concentration was estimated according to the method of Trevelyan and Harrison [103] and the Anthrone method of Brin [104]. Further details regarding the assay of an enzyme associated with trehalose metabolism were described by Barickman et al [96]. Trehalase activity was measured by activating phosphorylation with cAMP (cyclic adenosine monophosphate) and monitoring glucose levels [105].…”