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Fourteen F₅- and F₆-pedigrees, previously selected for a more vigorous seminal root system in a cross population of spring barley, were compared with their parents in the response to severe post-sowing drought and limited N- and P-supply. The materials were studied in glass-faced soil boxes, sand-vermiculite cultures and in the field. The F₅'s juvenile rooting superiority was not totally preserved for further growth stages suggesting partly different genetic backgrounds responsible for the seminal root system at various growth stages. Results indicated an absence of close genetic correlations between the seminal and adventitious root systems. The selected spring barley pedigrees exhibiting a more vigorous rooting benefit much more for their ability to avoid drought conditions than for their tolerance to nitrogen and phosphorus limitations. Especially under decreased N availability, the enhanced root extension in F₅ₛ resulted in a depressed shoot dry matter production. Despite a relatively low differentiation in the grain yield, some of the selected F₆-pedigrees were simultaneously found to indicate a high yield potential, an improved stability or tolerance to low-input.
On the basis of the field experiment carried out at the Experimental Station at Jadwisin (52°29’ N; 21°03’ E), Polish mid-early potato cultivar Triada was grown on sandy loam in years 2004 and 2005 in 6 treatments, which included the application of water and nitrogen: organic (cattle manure) and mineral. Water drip irrigation and nitrogen fertigation were scheduled by the Decision Support System (DSS). Diverse water supplies and organic or mineral nitrogen did not change harvest index (HI) values, which varied between 0.7 and 0.8 at the end of the growing period. Average tuber dry matter yield, about 11.0 t∙ha⁻¹, in both years of the investigation was reached with different HI values: 0.78 for 2004, and 0.73 for 2005. Higher percentage of biomass distributed to tubers was found in 2004, which was characterized by lower cumulative thermal time and global radiation, as well as better water balance in comparison with the growing period of 2005.
Atmospheric ozone remains depleted which in turn leads to the increase of UV-B radiation reaching the surface of the earth and in the same time more and more nitrogen will be imported into the terrestrial ecosystems through nitrogen deposition. These two factors will operate simultaneously. The photosynthetic and physiological responses of deciduous broad leaved species Swida hemsleyi occurring commonly at 1350–3700 m a.s.l. subjected to enhanced UV-B and to nitrogen supply were studied. The experimental design included two levels of UV-B treatments (ambient UV-B, 11.02 KJ m⁻² day⁻¹ and enhanced UV-B, 14.33 KJ m⁻² day⁻¹) and two nitrogen levels (without supplemental nitrogen supply and with supplemental nitrogen supply). An experiment was conducted in open semi-field condition in Maoxian Ecological Station of Chinese Academy of Sciences, Sichuan province, China at 1820 m a.s.l. Enhanced UV-B caused a marked decline in growth parameters, net photosynthetic rate, stomatal conductance to water vapour, chlorophyll pigments, whereas it induced an increase in rate of reactive oxygen species (ROS) production and ROS accumulation and malondialdehyde (MDA) content. Enhanced UV-B also induced an increase in leaf thickness and antioxidant compounds content, such as carotenoids and proline content. On the other hand, nitrogen supply caused an increase in some growth parameters, chlorophyll pigments and antioxidant compounds, and reduced ROS accumulation. However, nitrogen supply did not affect MDA content under enhanced UV-B, though it increased antioxidant compounds content and reduced the rate of ROS production and ROS accumulation. These results implied that enhanced UV-B brought harmful effects on Swida hemsleyi seedlings and supplemental nitrogen supply could alleviate the adverse effects of UV-B radiation on plants to some extent.
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