Water relations, mineral nutrition, growth, and13C discrimination in two apple cultivars under daily episodes of high root-medium temperature

Abstract

Although high soil temperatures can occur in apple orchards throughout the world, there is little information on their effect. This investigation was conducted to determine the influence of various durations of root exposure to 34 °C on the growth and physiology of the apple plant. Roots of Royal Gala and McIntosh cultivhrs were exposed to 34 °C for 0, 8,16, and 24 hours/day for seven weeks. Royal Gala grown at the 24 hours/day treatment exhibited significant decreases in leaf, shoot, and root growth; chlorophyll concentration of the older leaves; transpiration; discrimination against 13C in leaves; and an increase in leaf temperature. In McIntosh, root growth and chlorophyll concentration of leaves were not affected. For both cultivars compared to the control treatment, the continuous high temperature treatment resulted in lower levels of R Mg, and Mn in leaves. Royal Gala at this treatment showed significantly higher values of foliar N and K and lower values of Ca, Fe, and Zn. For McIntosh the levels of Cu and B decreased significantly in this treatment as compared to the control treatment. We conclude that 34 °C in the root-zone does not stress these cultivars unless it persists throughout the day/night cycle.

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

“…Possible explanations of how root-zone temperature influenced C assimilation include an alteration in water uptake, modification of the endogenous plant growth regulator balance, or absorption of nutrients (Behboudian et al, 1994). Water uptake was altered in the present study with transpiration rates decreasing with supraoptimum (i.e., >25 °C) root-zone temperatures (data not shown).…”

“…Water uptake was altered in the present study with transpiration rates decreasing with supraoptimum (i.e., >25 °C) root-zone temperatures (data not shown). This may have been a result of decreased levels of cytokinin-like substances in the roots and leaves (Gur et al, 1972) and also a possible increase in the synthesis of ABA resulting in stomatal closure (Behboudian et al, 1994). Other possible reasons for the root-zone temperature influence on net Pn include the mechanistic aspects of ion absorption and translocation (Natr, 1992).…”

“…Studies by Privé (1991) and Trinka (1991), however, indicated that these results may have been due to groundcover moisture conservation properties, and that warm root-zone temperatures may be optimum for raspberry growth. This unclear quantification of optimum root-zone temperature and results from an elevated daily root-zone temperature study with apples imply that net CO 2 exchange rate (NCER) may also be influenced by root-zone temperature (Behboudian et al, 1994). Hence, the objectives of this project were to 1) determine how whole-plant NCER is influenced by CO 2 concentration, whole-plant temperature, irradiation, and humidity and 2) quantify and differentiate the influence of air and root-zone temperature on NCER in raspberries.…”

Plant water relations influence carbon gain in a grass occurring along sharp gradients of soil temperature

“…Thus, soil temperatures often covary with other microclimate parameters, and the independent effects of soil temperatures on plants are difficult to identify, particularly under natural conditions in the field. Supraoptimal soil temperatures caused water stress, reduced nutrient uptake, and lower photosynthesis in crops (BassiriRad et al ., 1991; Behboudian et al ., 1994; Udomprasert et al ., 1995; Dodd et al ., 2000; He et al ., 2001). Correlations of high soil temperature and reduced uptake of soil water at midsummer for woody species of south‐west North America (Lin et al ., 1996; Williams & Ehleringer, 2000) indicate that the significance of warm soils to native plants may be more important than is currently appreciated.…”

The Effects of Elevated Root Zone Temperature on the Development and Carbon Partitioning of Spring Wheat

“…Increasing RZT from 25 to 30°C increases root-toshoot ratios (Awal et al, 2003) and can increase photosynthetic rates (Ziska, 1998). However, further increases in RZT can lead to growth inhibition by reducing nutrient uptake and chlorophyll content (Du and Tachibana, 1994), disturbing plant water relations and reducing g S (Behboudian et al, 1994) or altering plant chemical signaling (Dodd et al, 2000;Tachibana et al, 1997;Wang et al, 2004).…”