TY - JOUR

T1 - Growing Different Lactuca Genotypes Aeroponically within a Tropical Greenhouse—Cool Rootzone Temperatures Decreased Rootzone Ethylene Concentrations and Increased Shoot Growth

AU - Choong, Tsui-Wei

AU - He, Jie

AU - Lee, Sing K.

AU - Dodd, Ian Charles

PY - 2016/9/13

Y1 - 2016/9/13

N2 - Temperate crops cannot grow well in the tropics without rootzone cooling. As coolingincreased production costs, this experiment aimed to study the growth of various Lactucagenotypes and propose possible ways of reducing these costs, without compromisingproductivity. A recombinant inbred line (RIL) of lettuce and its parental lines (L. serriolaand L. sativa “Salinas”) were grown aeroponically in a tropical greenhouse under 24◦Ccool (C) or warm fluctuating 30–36◦C ambient (A) rootzone temperature (RZT). Their rootswere misted with Netherlands standard nutrient solution for 1 min, at intervals of either5 min (A5, C5) or 10 min (A10, C10) in attempting to reduce electricity consumptionand production costs. Lower mortality and higher productivity were observed in allgenotypes when grown in C-RZT. Higher shoot fresh weight was observed under C5than C10, for the RIL and L. serriola. Since “Salinas” had similar shoot fresh weightat both C-RZ treatments, this may indicate it is more sensitive to RZT than wateravailability. Under A-RZ treatments, higher carotenoid content, with correspondinglyhigher nonphotochemical quenching, was observed in A10 for the RIL and “Salinas.”Further, total chlorophyll content was also highest at this RZ treatment for the RIL thoughphotochemical quenching was contrastingly the lowest. Cumulatively, productivity wascompromised at A10 as the RIL seemed to prioritize photoprotection over efficiency inphotosynthesis, under conditions of higher RZT and lower water availability. Generally,higher RZ ethylene concentrations accumulated in A10 and C10 than A5 and C5,respectively—probably due to spray frequency exerting a greater effect on RZ ethyleneaccumulation than RZT. In the C5 RZ treatment, lowest RZ ethylene concentrationcorresponded with highest shoot fresh weight. As such, further research on ethylene(in)sensitivity and water use efficiency could be conducted to identify Lactuca cultivarsthat are better suited for growth in the tropics, so as to allay production costs withreduced cooling and spray intervals.

AB - Temperate crops cannot grow well in the tropics without rootzone cooling. As coolingincreased production costs, this experiment aimed to study the growth of various Lactucagenotypes and propose possible ways of reducing these costs, without compromisingproductivity. A recombinant inbred line (RIL) of lettuce and its parental lines (L. serriolaand L. sativa “Salinas”) were grown aeroponically in a tropical greenhouse under 24◦Ccool (C) or warm fluctuating 30–36◦C ambient (A) rootzone temperature (RZT). Their rootswere misted with Netherlands standard nutrient solution for 1 min, at intervals of either5 min (A5, C5) or 10 min (A10, C10) in attempting to reduce electricity consumptionand production costs. Lower mortality and higher productivity were observed in allgenotypes when grown in C-RZT. Higher shoot fresh weight was observed under C5than C10, for the RIL and L. serriola. Since “Salinas” had similar shoot fresh weightat both C-RZ treatments, this may indicate it is more sensitive to RZT than wateravailability. Under A-RZ treatments, higher carotenoid content, with correspondinglyhigher nonphotochemical quenching, was observed in A10 for the RIL and “Salinas.”Further, total chlorophyll content was also highest at this RZ treatment for the RIL thoughphotochemical quenching was contrastingly the lowest. Cumulatively, productivity wascompromised at A10 as the RIL seemed to prioritize photoprotection over efficiency inphotosynthesis, under conditions of higher RZT and lower water availability. Generally,higher RZ ethylene concentrations accumulated in A10 and C10 than A5 and C5,respectively—probably due to spray frequency exerting a greater effect on RZ ethyleneaccumulation than RZT. In the C5 RZ treatment, lowest RZ ethylene concentrationcorresponded with highest shoot fresh weight. As such, further research on ethylene(in)sensitivity and water use efficiency could be conducted to identify Lactuca cultivarsthat are better suited for growth in the tropics, so as to allay production costs withreduced cooling and spray intervals.

U2 - 10.3389/fphys.2016.00405

DO - 10.3389/fphys.2016.00405

M3 - Journal article

JO - Frontiers in Physiology

JF - Frontiers in Physiology

SN - 1664-042X

ER -