The Effects of Root Temperature on Growth, Physiology, and Accumulation of Bioactive Compounds of Agastache rugosa

Abstract

Plants respond to root temperature stresses by producing antioxidants as a defense mechanism. Since a number of these are phytochemicals with enhancing effects on human health, we examined the effects of 4 root-zone temperature (RZT) treatments (10, 20, 28, and 36 °C) on plant growth and the main bioactive compound concentrations in each organ of Agastache rugosa plants. We aimed to determine the optimal RZT treatment to increase bioactive compound concentrations with no deleterious effects on plant growth. Four-week-old seedlings were grown in a plant factory for 32 days. Nine plant growth parameters, namely, shoot and root fresh weights, stem and root lengths, leaf length and leaf width, leaf area, and shoot and root dry weights were significantly decreased at 10 and 36 °C compared with other treatments. A similar pattern was observed for the chlorophyll content and leaf gas exchange parameters. Of all the RZT treatments, RZT at 28 °C produced the significantly greatest accumulation of two major bioactive compounds, namely, rosmarinic acid (RA) and tilianin contents per the A. rugosa plant, and had no adverse effects on the overall growth of A. rugosa. This supports the use of 28 °C RZT to successfully improve the bioactive compounds with no adverse influence on plant growth or yield.

Nutrient Solution Temperature Affects Growth and °Brix Parameters of Seventeen Lettuce Cultivars Grown in an NFT Hydroponic System

“…Similar to our results, root-zone cooling at 20 • C increased the biomass of aeroponically grown lettuce from that in plants with ambient conditions (24 • C to 38 • C) in a tropical greenhouse [22]. Since the roots of plants are more sensitive to heat stress than the above-ground parts, the high rootzone temperature can easily damage the root, which can restrict the length and diameter of the stem [24]. High root-zone temperature (27.5 • C) resulted in water and nutrient loss in tomatoes (Solanum lycopersicum L.), which ultimately led to a reduction in plant growth [25].…”

Determination of total phenolic, flavonoids and antioxidant activity in Calligonum polygonoides L. from Thar Desert

“…High values for bio-active compounds possessed by phog plant might be due to its resource poor habitat in The Thar Desert which includes high and low temperature, extremly resource poor soil, soil salinity and a prolonged drought period. A recent report of Lam et al (2020) support this hypothese, they found that higher root zone temperature (28 ºC) drastically improved the accumulation of bioactive compounds in Agastache rugosa. Correlation analysis for phenolics, flavonoids and total antioxidant activity of different plant parts of C. polygonoides exhibited linear positive association among them (r = > 0.900) (Table 3).…”

Effects of Short-Term Root Cooling before Harvest on Yield and Food Quality of Chinese Broccoli (Brassica oleracea var. Alboglabra Bailey)

“…For example, Poire et al [29] reported that the leaf area and shoot fresh weight of Ricinus communis plants at lower root temperatures decreased throughout the experiment. In the experiment of Agastache rugosa, all plant growth parameters were restricted to cold root stress [13]. Plant growth of red leaf lettuce (Lactuca sativa L. cv.…”

“…Several studies have shown that long-term root cooling improves nutritional quality by increasing the levels of beneficial functional plant constituents. For example, after a 24-day root temperature treatment, the rosmarinic acid and acacetin concentration of Agastache rugosa was highest at 10 • C root temperature [13]. In hydroponically grown carrots, a 14-day treatment with an elevated nutrient solution temperature increased the total phenolic compounds and soluble solid content [10].…”