Growth and physiological responses of Picea asperata seedlings to elevated temperature and to nitrogen fertilization

Abstract

Picea asperata is a dominant species in the subalpine coniferous forests distributed in eastern edges of Tibetan Plateau and upper reaches of the Yangtze River. The paper mainly identified the short-term influences of experimental warming, nitrogen fertilization, and their combination on growth and physiological performances of Picea asperata seedlings. These seedlings were subjected to two levels of temperature (ambient; infrared heater warming) and two nitrogen levels (0; 25 g m -2 a -1 N) for 6 months. We used a free air temperature increase of overhead infrared heater to raise both air and soil temperature by 2.1 and 2.6°C, respectively. The temperature increment induced an obvious enhancement in biomass accumulation and the maximum net photosynthetic rate, and decreased AOS and MDA level under ambient nitrogen conditions. Whereas, negative effects of experimental warming on growth and physiology was observed under nitrogen fertilization condition. On the other hand, nitrogen fertilization significantly improved plant growth in unwarmed plots, by stimulating total biomass, maximum net photosynthetic rate (A max ), antioxidant compounds, as well as reducing the content of AOS and MDA. However, in warmed plots, nitrogen addition clearly decreased A max , antioxidant compounds, and induced higher accumulation of AOS and MDA. Obviously, the beneficial effects of sole nitrogen on growth and physiology of Picea asperata seedlings could not be magnified by artificial warming.

Nitrogen level affects growth and reactive oxygen scavenging of fenugreek irrigated with wastewater

“…This may be because it is a nitrogen-storage compound (Ahmad & Hellebust 1988) and that synthesis and accumulation of proline are stimulated by nitrogen supply (Sanchez et al 2002). This result is in agreement with the findings of many workers (Naidoo & Naidoo 2001, Sanchez et al 2001, 2002, Zhao & Liu 2009, Ahmadi et al 2010, Wang et al 2011.…”

“…These metals might have contributed to increased MDA levels (Olorunfemi & Lolodi 2011). Reduction of MDA content due to nitrogen application was probably due to increased activity of antioxidant enzymes (Shin et al 2005, Zhao & Liu 2009, Lin et al 2011. Xiao et al (1998) reported that nitrogen application can improve light reaction of photosynthesis which ultimately leads to the lower ROS production.…”

“…Williams et al (1967) suggested that addition of nitrogen in soil increases the formation of NO 3 -which decreases soil pH. Lowering pH increases the solubility of heavy metals and decrease the efficiency of adsorption (Moreno et al 2000, Zhao & Liu 2009, Ahmadi et al 2010, Lin et al 2011.…”

Positive effects of night warming on physiology of coniferous trees in late growing season: Leaf and root

“…It is reported that globally averaged maximum and minimum temperatures have both increased since 1950 (IPCC, 2013), which tends to affect carbon assimilation and consumptions in plants, because photosynthesis in most plants occurs during the daytime and is more sensitive to daily maximum temperature, whereas plants respiration occurs throughout the whole day (Atkin et al, 2013), and is therefore influenced by both daily maximum and minimum temperature (Peng et al, 2013). To our knowledge, a great deal of attention has been focused primarily on continuous warming or day warming (Zhao and Liu, 2009;Zheng et al, 2013), while little is known about the effect of night warming on trees, especially on their root N uptake rates.…”

Belowground responses of Picea asperata seedlings to warming and nitrogen fertilization in the eastern Tibetan Plateau

“…Our previous study results showed that warming increased photosynthetic rates and the aboveground biomass of dragon spruce (Picea asperata) seedlings (Yin et al 2008;Zhao and Liu 2009a), and nitrogen fertilization significantly improved plant aboveground growth (Zhao and Liu 2009a). However, it remained unclear whether belowground growth, root/shoot ratio, and carbon and nitrogen allocation above-and belowground will change consistently with aboveground parameters under warming, enrichment of soil N or a combination of both?…”