ARS | Publication request: NIGHTTIME TRANSPIRATION AND NUTRIENT ACQUISITION: IS THERE A BENEFIT OF LOSING WATER AT NIGHT?

Submitted to: Ecological Society of America Bulletin
Publication Type: Abstract
Publication Acceptance Date: April 19, 2005
Publication Date: August 7, 2005
Citation: James, J.J. 2005. Nighttime transpiration and nutrient acquisition: Is there a benefit of losing water at night [abstract]? Ecological Society of America Bulletin. Paper No. 93.

Technical Abstract: Nighttime stomatal conductance and transpiration can lead to a substantial amount of water loss occurring at non-photosynthetic times in C3 and C4 plants. Water loss without simultaneous carbon gain is intuitively wasteful, however it is possible that either the phenomenon is not a cost under non-water limiting conditions or that it provides a benefit under certain conditions. For example, the transpiration stream is largely responsible for supplying soil-mobile nutrients (e.g. nitrate) to plant roots, and it is hypothesized that the maintenance of water flux through the soil-plant-air continuum through nighttime transpiration (NT) could enhance nutrient supply to plant roots. In a growth chamber study with 3 ecotypes of Arabidopsis thaliana, nighttime relative humidity was manipulated to suppress or allow NT in plants given two levels of nitrogen. N-limited plants grown under high nighttime relative humidity (~90%) showed decreased plant fitness relative to plants in which NT was not suppressed (~55% RH), indicating that under non-water-limiting conditions, NT benefited N-limited plants. Results for non-N-limited plants varied among ecotypes, thus relative costs and benefits depending on nutrient availability. In a separate field study, Helianthus anomalus plants given nutrient additions showed decreased day and night conductance and transpiration. To explore the extent to which NT might affect the supply of mobile nutrients to plant roots, the Barber-Cushman model was used to investigate depletion of nitrate at various distances from a rooting zone under different levels of water flux through the system. Results showed that increasing water flux through the system (as with NT) increased N supply to plant roots. A preliminary field study using the desert shrub Sarcobatus vermiculatus showed that actual plant uptake of 15N decreased slightly when NT was suppressed, although differences were not significant due to low sample sizes.