Influence of High Shoot and Root‐Zone Temperatures on Growth of Three Wheat Genotypes during Early Vegetative Stages

Abstract

Keywords high shoot/root-zone temperature; net assimilation rate; relative growth rate; specific root weight; wheat; xylem sap flow rate Correspondence I. AbstractHigh temperatures, whether of shoot or root, are reported to affect shoot and root growth of various plant species. The scanty information available on the differential response of wheat genotypes to high shoot and root-zone temperatures triggered this investigation to study the response and adaptation of shoot and root growth of three wheat genotypes to high shoot and root-zone temperatures during early growth stages. Three wheat genotypes; Fang (heat tolerant), Siete Cerros (heat sensitive) and Imam (recent cultivar adapted to a hot irrigated environment) were grown in soil and hydroponically. Three shoot/rootzone temperatures (23/23, 23/35 and 35/35°C for the soil experiment and 22/22, 22/38 and 38/38°C for the hydroponic experiment) were applied at three-leaf growth stage. High root-zone temperature alone or combined with high shoot temperature reduced xylem sap flow rate, root dry weight, root length and root/shoot ratio. Unexpectedly, shoot fresh and dry weights and relative growth rate (RGR) were not significantly affected by the high root-zone temperature except for the susceptible genotype, Siete Cerros, after prolonged exposure in the hydroponic experiment. In contrast, high shoot/root-zone temperature significantly reduced shoot fresh and dry weights from as early as the first week of the hydroponic experiment. The 38/38°C treatment also caused significant reduction in RGR and net assimilation rate during the first 2 weeks, but no significant differences were found during the last 2 weeks compared with 22/22°C. Interesting responses were observed among genotypes in terms of shoot and root dry weights and root/shoot ratio at 38/38°C treatment. The heat-sensitive Siete Cerros showed the least reduction in these traits during the first 2 weeks while the heat-tolerant Fang and Imam responded by greatly reducing their shoot and root weights. The situation was almost reversed with the duration of treatments such that Siete Cerros became the most affected genotype while Fang and Imam were better adapted to high shoot/root-zone temperature. Specific root weight was the exceptional trait that increased under high temperature treatments. Results indicate that despite the reduction in root length and weight observed under high root-zone temperature, shoot growth was not much affected suggesting that the use of suitable cultivar coupled with proper management could alleviate most of high root-zone temperature effects during early growth stages.

Supra‐optimal growth temperature exacerbates adverse effects of low Zn supply in wheat

“…Apparently, supra‐optimal temperatures can affect root growth at a higher extent as compared to shoot growth as observed in the current and other studies ( Tahir et al., ; Heckathorn et al., ). For example, many have reported that increasing the root‐zone temperature is more detrimental than increasing the ambient air temperature for root and shoot growth and that increasing the root‐zone temperature alone can result in inhibition of shoot growth (reviewed in Huang et al., ).…”

Effects of Soil Temperature on Growth and Root Function in Rice

“…1). Decrease of root weight and root/shoot ratio at high soil temperatures compared with control temperatures of 22-24ºC has been reported in other crops: grass at 35ºC (Xu and Huang, 2000a), wheat at 35ºC (Tahir et al, 2008) and tree of heaven (Ailanthus altissima) at 34ºC (Graves et al, 1991). The optimum soil temperature for root growth ranges from 10-18ºC in most cool-season grasses (Fly and Huang, 2004), and is about 20ºC in cucumbers (Tachibana, 1982).…”

“…In this study, root respiration, and uptake of water and nutrients might be stimulated by high soil temperature until 7 DAT. Inhibition of water uptake by long-term elevation of soil temperature was observed in tree of heaven (Graves et al, 1991) and wheat (Tahir et al, 2008); that of root respiration was observed in tomatoes (Klock et al, 1997). The nitrogen and water absorption in rice decreased by long-term elevation of water temperature at 37ºC (Baba, 1958).…”

“…), and apple trees (Malus sylvestris Mill. ), supraoptimal root temperature caused negative effects on shoot and root growth (Du and Tachibana, 1994a;Gur,et al, 1972;Lyons et al, 2007;Xu and Huang, 2000a), photosynthesis and carbohydrate metabolism (Du and Tachibana, 1994b;Xu and Huang, 2000b), and water and nutrient uptake (Huang and Xu, 2000;Klock et al, 1997;Tahir et al, 2008). The production of cytokinins and abscisic acid (ABA) in roots has been suggested to have a significant role in regulating shoot growth and photosynthesis under high soil temperature in wheat and grass (Liu and Huang, 2005).…”

Improved root zone temperature buffer capacity enhancing sweet pepper yield via soil-ridged substrate-embedded cultivation in solar greenhouse

“…PG without soil covering could not buffer the high root zone temperature, and consequently inhibited the growth and fruit yield of sweet pepper compared to other treatments due to high root zone temperature [30,31] . Previous studies showed that the effects of high root zone temperature on plants were more apparent than those of high air temperature [18,32] . For example, a high root zone temperature reduced the accumulation of dry matter and affected the growth of sweet pepper [33] .…”