Search Results

How are C and N metabolites affected by a root-zone temperature (RZT) in phase or out of phase with the photoperiod? Tomato (Lycopersicon esculentum Mill.) was grown with an air temperature of 20C, and RZT that was in phase with a 12-h photoperiod, 28C in the light and 12C in the dark, or out of phase, 12C in the light and 28C in the dark. Seedlings were grown in flowing solution containing 200 μm NO₃ and excess amount of other mineral elements. The flow rate increased with plant size. After 8 days, plants were harvested at the end of the day and at the end of the night. The relative growth rate (day^–1) was slightly greater for in-phase (0.19) than out-of-phase RZT (0.17) and less than that at a constant air and RZT of 24C (0.22). RZT affected N accumulation and partitioning of C and N metabolites. Cool roots contained more NO₃ and free sugars than warm roots. Leaves had less NO₃ in the light than in the dark, and NO₃ in leaves of plants with an out-of-phase RZT was depleted in the light. Concentration of free amino acids and protein was greater and the amount of starch was less in leaves of plants with in-phase RZT.

What is the effect of constant compared to diurnal heating of the shoot and root on growth and yield of greenhouse tomato (Lycopersicon esculentum L.)? Seedlings were transplanted on 4 or 25 Mar. 1994 into troughs that were not heated or heated to 21C by buried tubing, either constantly or for 12 h during the day or the night. The greenhouses had either 14/14C or 26/6C day/night minimum air temperatures. After 2 weeks, leaves of the 4 Mar. transplants weighed most with constant root heat and least with no heat. Roots weighed more with 14/14C than 26/6C air heat. With 14/14C air heat, only no root heat reduced leaf weight, whereas with 26/6C air heat, leaf weight was in the order: constant > day > night - no heat. After 2 weeks, leaves of the 25 Mar. transplants weighed least with no heat, and other treatments did not differ. Root heating affected yield. By 1 July, the number of fruit and the number and weight of marketable fruit produced from 4 Mar. transplants was in the order: constant heat > day > night > no heat. The 22/6C air heat increased marketable yield because fewer fruit were small, irregular, or had blossom-end rot. Root heat had no effect on yield of 25 Mar. transplants.

Tomato (Lycopersicon esculentum Mill) seedlings were grown with air temperature of 28°C light/12°C dark (12/12 hours), and either a constant, 20°C, root-zone temperature (RZT), or in-phase with air temperature, 28°C in the light and 12°C in the dark, or out-of-phase, 12°C in the light and 28°C in the dark. These treatments were applied from 17 to 25 days after germination, with 200 m ${\text{NO}}_3^{-}$ in flowing nutrient solution. The relative growth rate of leaves was the greatest with constant RZT, 0.33/d, and least with out-of-phase RZT, 0.29/d. The concentration of free amino acid and protein in leaves was least for out-of-phase RZT. The ${\text{NO}}_3^{-}$ concentration in leaves was the highest in the dark, intermediate in the middle of the light period, and the lowest at the end of the light period. In roots, ${\text{NO}}_3^{-}$ concentration showed a similar trend. This variation was greatest when RZT was varied out of phase, and least with constant RZT. At the end of the light period, ${\text{NO}}_3^{-}$ concentration in roots was 246, 180, and 162 μmol·g^–1 dry weight for constant, in phase, and out of phase RZT, respectively. In the light, leaves of seedlings grown with out-of-phase RZT had 5 mmol·g^–1 ${\text{NO}}_3^{-}$ , compared to 16 mmol·g^–1 with in-phase RZT Availability of ${\text{NO}}_3^{-}$ in the light may be the factor limiting plant growth with out-of-phase RZT. This research was supported in part by grant number 93-37100-9101 from the National Research Initiative Competitive Grants Program/USDA.