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Relationship among nitrogen nutrition, photoperiod and photoperiodic injury in tomato (Solanum lycopersicum)

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dc.contributor.advisor Micallef, Barry J. Orozco Gaeta, Maria Emilia 2012-10-03T19:55:28Z 2012-10-03T19:55:28Z 2012-08 2012-08-16 2012-10-03
dc.description.abstract This thesis is an investigation of photoperiodic injury (PI) in tomato plants and practices to alleviate the problem. PI is a physiological disorder characterized by chlorosis and necrosis of leaves when plants are grown under either long photoperiods or non-24 h light/ dark cycles. Solanum lycopersicum L. (tomato) is particularly susceptible to PI. Our group has shown a correlation between PI and altered circadian expression patterns for the nitrate assimilatory enzymes nitrate reductase (NR) and nitrite reductase (NiR) in tomato, resulting in accumulation of the toxic metabolite nitrite, particularly at specific times of day (TOD) when the NiR/NR activity ratio is low. We hypothesized that accumulation of nitrite and PI can be alleviated by altering nitrate nutrition at specific times of day and the use of an air temperature differential. The tomato cultivars ‘Micro Tom’ (PI-tolerant) and ‘Basket Vee’ (PI-susceptible) were grown under various photoperiod regimes to determine: (1) if a positive correlation exists between PI and nitrite accumulation as determined by visual assessment, and chlorophyll and nitrite quantification; (2) if 24 h light affects the diel pattern of nitrate uptake in a way that favours PI through measurements of nitrate depletion; and (3) if PI can be alleviated by altering nitrate nutrition at two specific TOD when tomato is susceptible to nitrite accumulation. A positive correlation was found between nitrite accumulation and PI. Nitrate uptake experiments showed that the nitrate uptake rate per se is not responsible for PI in tomato, but maintenance of circadian nitrate uptake patterns even in 24 h light in combination with a loss of the circadian patterns for NR and NiR activities could contribute to PI. Nitrite accumulation and PI was decreased by utilizing a nutrient solution containing 25% total nitrogen at two specific 4 h periods in the day when tomato is susceptible to nitrite accumulation. We call this new technique TOD fertigation. Time-of-day fertigation in combination with a 6 oC temperature differential further reduced nitrite accumulation and PI. These findings showed the response of greenhouse tomatoes to supplemental lighting and the potential for increasing the photoperiod threshold for PI. en_US
dc.description.sponsorship The Mexican Council for Science and Technology (CONACYT); The Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA) en_US
dc.language.iso en en_US
dc.subject nitrate uptake en_US
dc.subject chlorosis en_US
dc.subject low nitrogen nutrient solution en_US
dc.subject temperature differential en_US
dc.title Relationship among nitrogen nutrition, photoperiod and photoperiodic injury in tomato (Solanum lycopersicum) en_US
dc.type Thesis en_US Plant Agriculture en_US Doctor of Philosophy en_US Department of Plant Agriculture en_US

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