4.2 Root zone warming treatments
Flat heating plates were placed on a growth chamber table and
alternately operated for 15 minutes/ and ceased heating for 15 minutes
for 10 hours/day. No heating was applied for the subsequent 14 h. Each
cycle of RZW was 24 h composed of 10 h with intermittent warming, and 14
h without. Disposable aluminum trays (30X40 cm) containing 7-10 mm
height of tap water were placed over the heaters and 800 ml pots with
six week old tomato plants were placed in the aluminum trays. The plants
were fertilized with slow release fertilizer (1 g each, Osmocote,
Everris International BV, Heerlen, The Netherlands) containing N (18%),
P2O5 (9%), K2O (10%),
MgO (2%), Fe (0.3%), Mn (0.04%), Cu (0.037%), Zn (0/011%), B
(0.1%), Mo (0.015%) and water was added daily to the pots. Temperature
at 5 cm depth of the mock and treated pots reached 21±1 and 28±1ºC
during the warming period while the canopy temperatures were 18-21ºC
during the entire experiment. This experimental design aimed at
mimicking real agricultural conditions, where natural daytime soil
heating in different settings can result in root zone warming while the
plant canopy remains at lower temperatures (Elad et al., 2016a).
Incubation took place in an illuminated, air conditioned growth chamber
with 21±1ºC and 2200 Lux light intensity, 12h daylight.