PHOTOSYNTHESIS AND NITROGEN METABOLISM OF HEAT-RESISTANT AND HEAT-SENSITIVE RECOMBINANT INBRED LINES (RILS) OF LETTUCE UNDER DIFFERENT ROOT-ZONE TEMPERATURES
Two heat-resistant (HR) and two heat-sensitive (HS) lettuce recombinant inbred lines (RILs) and their parental lines [Lactuca sativa (maternal, HS) and L. serriola (paternal, HR)] were grown aeroponically at two initial root-zone temperatures (RZTs): ambient-RZT (A-RZT) and 25°C-RZT (C-RZT) in full strength Netherlands Standard Nutrient Solution. The aerial parts of all plants were maintained at fluctuating ambient temperatures of 26-36°C. Three weeks after transplanting, reciprocal RZT transfer of half the plants resulted in four RZT treatments: C-RZT, A-RZT, C→A-RZT and A→C-RZT. Productivity, photosynthesis and N metabolism were determined as shoot and root fresh weight (FW), maximal photosynthetic CO2 assimilation (A sat) and stomatal conductance (gs sat) and NO3- and total reduced N (TRN) concentrations. Lettuce grown at C-RZT had the highest shoot and root FW across all lines. Shoot and root FW of HR lettuce RILs were significantly higher than that of HS lettuce RILs at A-RZT. NO3- and TRN concentrations were significantly higher in shoots than roots but there were no clear relationship between productivity and N metabolism among the different lines under different RZTs. A sat showed no significant differences between HR and HS lettuce RILs under different RZTs except for a lower A sat observed in the maternal line (HS). There was no clear relationship between A sat, gs sat, and productivity. Possible mechanism(s) responsible for the variation in productivity among HR and HS lettuce RILs and their parental lines grown under different RZTs are discussed.
He, J., Seet, L.T.L., Choong , T.W., Qin , L. and Dodd , I.C. (2013). PHOTOSYNTHESIS AND NITROGEN METABOLISM OF HEAT-RESISTANT AND HEAT-SENSITIVE RECOMBINANT INBRED LINES (RILS) OF LETTUCE UNDER DIFFERENT ROOT-ZONE TEMPERATURES. Acta Hortic. 1004, 165-172
aeroponic culture, heat-resistant, heat sensitive, nitrogen metabolism, photosynthesis