Effects of Root-zone Temperature on the Growth of Anthurium andraeanum Potted Plants

Anthurium andraeanum Hort. is a perennial herbaceous plant suitable for indoor plantscape. In Taiwan, Anthuriums are produced year-round under shade houses without temperature controlled. Low temperatures during winter result in slow growth and lower yield. Heating is not practical under shadehouses and increase production cost significantly. On the other hand, high temperatures during summer would reduce growth. In practical, adjusting root-zone temperature would be an alternative to enhance plant growth. This study was to determine the optimal temperature range of potted Anthurium ‘True Love’ in sand or hydroponics system.
During winter to spring at air temperatures of 13-29℃, young plants of Anthurium ‘True Love’ were treated with root temperatures 18 (unheated), 21 and 24℃ for 120 days. At 5 to 24 days after treatments, Fv/Fm value (maximum photosystemII efficiency) was higher in plants with 21 and 24℃than unheated treatment. Plants grown without heating had lower SPAD values. Bottom heating at 21 or 24℃ could reduce number of chlorotic and necrotic leaves. At 120 days after treatments, plants at 21℃ had higher plant dry weight than those at 18 and 24℃ treatments.
During winter at air temperature of 18-29℃, plants were grown with root temperatures of 17 (unheated), 21, 25, 31, and 38℃. Leaf number, leaf area, net photosynthesis rate, and stomatal conductance were lower when root temperature increased to 31-38℃. Leaf yellowing appeared in plants grown at 38℃. Whole plant dry weight was the highest when treated with 18 and 21 oC and the lowest in 38℃ treatment. Shoot dry weight decreased when root temperature increased from 25℃ to 31-38℃. Shoot dry weight did not differ in the 17-25℃ treatments.

In Expt. 3, plants were grown with root temperatures of 20, 24, and 32℃ at air temperatures of 13-27℃ during spring. Within 14 days after treatments, Fv/Fm value (0.7-0.8) did not differ between treatments. Root temperature of 32℃ significantly reduced net photosynthesis rate. Higher root temperature at 32℃ resulted in significant increase of chlorotic and necrotic leaves and decreases of SPAD value and leaf area. Shoot dry weights in plants of 20 and 24℃ treatment were higher than those grown at 32℃. Root temperature of 32℃ significantly reduced shoot and root nitrogen (N), phosphorus (P), and potassium (K) concentrations and whole plant content of N, P, K, calcium, and magnesium.

In Expt. 4, potted plants were grown in hydroponics, with air temperatures of 15-30℃ in a growth chamber during spring. Root temperatures of 15, 20 (control), 21, 24, and 28℃ were set. Within 13 days after treatment, Fv/Fm value did not significantly differ between treatments. Net photosynthesis rate (Pn), stomatal conductance (gs), leaf number, leaf area, and number of flowers increased when root temperature increased from 15 to 20℃. A further increase in root temperature to 28℃ caused significant decrease in Pn, gs, leaf number and leaf area. At 92 days after treatment, plants grown with root temperature 20℃ had higher whole plant, shoot, and root dry weights than those grown with 15 and 28℃. Treatments at 20 and 28℃ had the lowest and highest root malonyldialdehyde (MDA) content at 39 days after treatment, respectively. Plants grown with root temperatures of 15 and 20℃ had higher MDA content at 53 days after treatment (DAT) than at 39 DAT. Root temperature at 24℃ resulted in a lower MDA content at 53 DAT.