Whole-plant Net CO2 Exchange of Raspberry as Influenced by Air and Root-zone Temperature, CO2 Concentration, Irradiation, and Humidity

Abstract

<jats:p>The influence of irradiance, CO<jats:sub>2</jats:sub>, and temperature on whole-plant net CO<jats:sub>2</jats:sub> exchange rate (NCER) of <jats:italic>Rubus idaeus</jats:italic> L. `Heritage' micropropagated raspberries was examined. Within the set of environmental conditions examined, irradiation was the most important factor, accounting for 58% of the whole-plant irradiance/CO<jats:sub>2</jats:sub> concentration/temperature NCER model variation, followed by CO<jats:sub>2</jats:sub> concentration (28%) and temperature (2.5%). Net photosynthesis (Pn) required irradiance levels &gt;600 μmol·m<jats:sup>-2</jats:sup>·s<jats:sup>-1</jats:sup> <jats:italic>PPF</jats:italic> for saturation, greatly increased under CO<jats:sub>2</jats:sub> enrichment (up to 1500 μL·L<jats:sup>-1</jats:sup>), and was optimum at a whole-plant temperature of 20 °C. Temperature effects were partitioned in an experiment using varying air and root-zone temperatures (15, 20, 25, 30, and 35 °C) under saturated light and ambient CO<jats:sub>2</jats:sub> levels (350 μL·L<jats:sup>-1</jats:sup>). Air and root-zone temperature influenced Pn, with maximum rates occurring at an air × root-zone temperature of 17/25 °C. The contribution of air and root-zone temperature to the NCER model varied, with air and root-zone temperature contributing 75% and 24%, respectively, to the total model variation (<jats:italic>R</jats:italic><jats:sup>2</jats:sup> = 0.96). Shoot dark respiration increased with air and root-zone temperature, and root respiration rates depended on air and root-zone temperature and shoot assimilation rate. Humidity also influenced Pn with a saturated vapor pressure deficit threshold &gt;0.25 kPa resulting in a Pn decrease. Quantifying the physiological response of raspberries to these environmental parameters provides further support to recent findings that cool shoot/warm root conditions are optimum for raspberry plant growth.</jats:p>

Persistent negative temperature response of mesophyll conductance in red raspberry (Rubus idaeus L.) leaves under both high and low vapour pressure deficits: a role for abscisic acid?

“…Net photosynthesis in red raspberry is optimal below 25 °C, peaking typically around 17–21 °C (Percival et al . ; Stafne et al . ; Hall & Sobey ).…”

“…In this study, we evaluated the short-term temperature response of g m in red raspberry (Rubus idaeus L.), an economically important horticultural crop of northern hemisphere origins, which readily adapts to cool temperate climatic conditions (Hall & Sobey 2013). Net photosynthesis in red raspberry is optimal below 25°C, peaking typically around 17-21°C (Percival et al 1996;Stafne et al 2001;Hall & Sobey 2013). We evaluated g m from 20 to 35°C, which is representative of the maximal daytime T leaf differential experienced by raspberry leaves out in the open field on sunny summer days in southern Québec where plants were obtained.…”

Review: Characterization and Impact of Supraoptimal Root-zone Temperatures in Container-grown Plants

“…Leaf chlorophyll content of Freeman maple cultivars was reduced by a constant RZT of 34°C compared with 28°C for 32 d (Wilkins et al, 1995). Air temperature and RZT in the range of 15 to 35°C influenced CO 2 assimilation in Rubus idaeus L. 'Heritage', with maximum rates occurring at an air temperature/RZT of 17/25°C (Percival et al, 1996). High RZT in Prunus mira Koehne (smoothpit peach) seedlings decreased leaf water content and decreased photosynthesis (Hao et al, 2012).…”

Whole-plant respiration and its temperature sensitivity during progressive carbon starvation

“…A. crenata is a very slow-growing shade-tolerant plant (Kitajima et al 2006), and growth respiration may be low relative to maintenance respiration. Previous studies have found low Q 10 values of whole-plant respiration, often lower than 1.5 (Percival et al 1996;Frantz et al 2004), but in these other species, growth respiration was proportionally higher than in A. crenata. A. crenata grows in the understorey of warm to temperate evergreen forests in its native environment in Japan and also in Florida (Kitajima et al 2006).…”