Effects of enhanced UV-B radiation on the distribution of mineral elements in soybean (Glycine max) seedlings

Effect of irradiation and canopy position on anatomical and physiological features of Fagus sylvatica and Quercus petraea leaves

Growing conditions at different tree canopy positions may significantly vary and lead to foliar changes even within the same tree. An assessment of foliar anatomy, including also epidermal features, can help us understand how plants respond to environmental factors. Working with two model tree species (i.e., Quercus petraea and Fagus sylvatica) grown at their southernmost European distribution area in Central Spain, the influence of irradiation and canopy height was examined by sampling lower canopy leaves and comparing them with fully irradiated, top canopy leaves and shaded top canopy leaves grown for months within a bag made of shade netting fabric before they sprouted. At the end of the summer, samples were collected, and several parameters were analysed. The results indicate that SLA (specific leaf area) differences are significant both between species and groups. Leaf and cuticle thickness differed significantly between groups while stomatal densities only between species. Regarding mineral concentrations, differences between species were significant for K, Mn, N and N: P ratios. It is concluded that leaf responses to environmental conditions may be variable both within the same tree and between species.

Seedling growth, physiological characteristics, nitrogen fixation, and root and nodule phytase and phosphatase activity of a low-phytate soybean line

Understanding the influence of the valuable "low-phytate" trait on soybean seedling growth, physiology, and biochemistry will facilitate its future exploitation. The aim was to elucidate the physiological and biochemical characteristics of low-phytate (LP) soybean at the seedling stage. To this end, seed P and mineral content and seedling dry weight, carbon (C) and nitrogen (N) accumulation, nitrogen fixation, and root and nodule phytase and phosphatase activity levels were measured at 21 d after sowing LP and normal-phytate (NP) soybean lines. Seedling dry weight, and C and N accumulation were 31%, 38% and 54% higher, respectively, in the LP line than the NP line. The total and specific nitrogen fixation levels in the LP nodules were 46% and 78% higher, respectively, than those in the NP nodules. The phytase, phosphatase, and specific phytase levels were 1.4-folds, 1.3-folds, and 1.3-folds higher, respectively, in the LP roots than the NP roots. The phosphatase and specific phosphatase levels in LP nodules were 1.5-folds and 1.3-folds higher, respectively, than those in the NP nodules. The mineral levels were substantially higher in the LP seeds and seedings than in those of the NP line. The HCl extractabilities of P, S, Fe, Cu and Mn were higher in the LP seeds than the NP seeds. These results indicate that the LP line presented with superior seedling growth and nitrogen fixation relative to the NP line. The LP line had relatively higher root phytase and root and nodule phosphatase activity levels than the NP line and could, therefore, be better suited and more readily adapt to low P conditions.

Effects of elevated ultraviolet-B radiation on root growth and chemical signaling molecules in plants

Ozone layer depletion leads to elevated ultraviolet-B (UV-B) radiation, which affects plant growth; however, little is known about the relationship between root growth and signaling molecules in roots. Therefore, in this work, simulated UV-B radiation was used to study the effects of elevated UV-B radiation on root growth of soybean seedlings and changes in the content of signaling molecules in roots. The results showed that compared with the control, the 2.63 kJ m-2 d-1 and 6.17 kJ m-2 d-1 elevated UV-B radiation treatments inhibited root growth, and root growth parameters (total root length, root surface area, root volume, average diameter, root tip number, and root dry weight) all decreased. For root signaling molecules, the content of nitric oxide, reactive oxygen species, abscisic acid, salicylic acid, and jasmonic acid increased, and the content of auxin, cytokinin, and gibberellin decreased. The above indices changed more significantly under the 6.17 kJ m-2 d-1 treatment. After withdrawal of the exposure, the above indices could be restored to a certain extent. These data indicated that UV-B radiation interfered with root growth by affecting the content of signaling molecules in roots, and the degree of the effects was related to the intensity of UV-B radiation. The results from this study provide a theoretical basis for studying the preliminary mechanism of elevated UV-B radiation on root growth and possible pathways that can mitigate UV-B radiation damage for root growth. ONE SENTENCE SUMMARY: The effects of elevated UV-B on root growth of soybean seedlings were regulated by signaling molecules, and the degree of the effects was related to the intensity of UV-B radiation.

Combined effects of Lanthanum(III) and elevated Ultraviolet-B radiation on root nitrogen nutrient in soybean seedlings

Rare earth element pollution and elevated ultraviolet-B (UV-B) radiation occur simultaneously in some regions, but the combined effects of these two factors on plants have not attracted enough attention. Nitrogen nutrient is vital to plant growth. In this study, the combined effects of lanthanum(III) and elevated UV-B radiation on nitrate reduction and ammonia assimilation in soybean (Glycine max L.) roots were investigated. Treatment with 0.08 mmol L(-1) La(III) did not change the effects of elevated UV-B radiation on nitrate reductase (NR), nitrite reductase (NiR), glutamine synthetase (GS), glutamate synthase (GOGAT), glutamate dehydrogenase (GDH), nitrate, ammonium, amino acids, or soluble protein in the roots. Treatment with 0.24 mmol L(-1) La(III) and elevated UV-B radiation synergistically decreased the NR, NiR, GS, and GOGAT activities as well as the nitrate, amino acid, and soluble protein levels, except for the GDH activity and ammonium content. Combined treatment with 1.20 mmol L(-1) La(III) and elevated UV-B radiation produced severely deleterious effects on all test indices, and these effects were stronger than those induced by La(III) or elevated UV-B radiation treatment alone. Following the withdrawal of La(III) and elevated UV-B radiation, all test indices for the combined treatments with 0.08/0.24 mmol L(-1) La(III) and elevated UV-B radiation recovered to a certain extent, but they could not recover for treatments with 1.20 mmol L(-1) La(III) and elevated UV-B radiation. In summary, combined treatment with La(III) and elevated UV-B radiation seriously affected nitrogen nutrition in soybean roots through the inhibition of nitrate reduction and ammonia assimilation.

Influence of UV radiation on chlorophyll, and antioxidant enzymes of wetland plants in different types of constructed wetland

A surface- and vertical subsurface-flow-constructed wetland were designed to study the response of chlorophyll and antioxidant enzymes to elevated UV radiation in three types of wetland plants (Canna indica, Phragmites austrail, and Typha augustifolia). Results showed that (1) chlorophyll content of C. indica, P. austrail, and T. augustifolia in the constructed wetland was significantly lower where UV radiation was increased by 10 and 20 % above ambient solar level than in treatment with ambient solar UV radiation (p < 0.05). (2) The malondialdehyde (MDA) content, guaiacol peroxidase (POD), superoxide dismutase (SOD), and catalase (CAT) activities of wetland plants increased with elevated UV radiation intensity. (3) The increased rate of MDA, SOD, POD, and CAT activities of C. indica, P. australis, and T. angustifolia by elevated UV radiation of 10 % was higher in vertical subsurface-flow-constructed wetland than in surface-flow-constructed wetland. The sensitivity of MDA, SOD, POD, and CAT activities of C. indica, P. austrail, and T. augustifolia to the elevated UV radiation was lower in surface-flow-constructed wetland than in the vertical subsurface-flow-constructed wetland, which was related to a reduction in UV radiation intensity through the dissolved organic carbon and suspended matter in the water. C. indica had the highest SOD and POD activities, which implied it is more sensitive to enhanced UV radiation. Therefore, different wetland plants had different antioxidant enzymes by elevated UV radiation, which were more sensitive in vertical subsurface-flow-constructed wetland than in surface-flow-constructed wetland.

Combined effects of lanthanum(III) and elevated ultraviolet-B radiation on root growth and ion absorption in soybean seedlings

Rare earth element accumulation in the soil and elevated ultraviolet (UV)-B radiation (280-315 nm) are important environmental issues worldwide. To date, there have been no reports concerning the combined effects of lanthanum (La)(III) and elevated UV-B radiation on plant roots in regions where the two issues occur simultaneously. Here, the combined effects of La(III) and elevated UV-B radiation on the growth, biomass, ion absorption, activities, and membrane permeability of roots in soybean (Glycine max L.) seedlings were investigated. A 0.08 mmol L(-1) La(III) treatment improved the root growth and biomass of soybean seedlings, while ion absorption, activities, and membrane permeability were obviously unchanged; a combined treatment with 0.08 mmol L(-1) La(III) and elevated UV-B radiation (2.63/6.17 kJ m(-2) day(-1)) exerted deleterious effects on the investigated indices. The deleterious effects were aggravated in the other combined treatments and were stronger than those of treatments with La(III) or elevated UV-B radiation alone. The combined treatment with 0.24/1.20 mmol L(-1) La(III) and elevated UV-B radiation exerted synergistically deleterious effects on the growth, biomass, ion absorption, activities, and membrane permeability of roots in soybean seedlings. In addition, the deleterious effects of the combined treatment on the root growth were due to the inhibition of ion absorption induced by the changes in the root activity and membrane permeability.

Lanthanum (III) regulates the nitrogen assimilation in soybean seedlings under ultraviolet-B radiation

Ultraviolet-B (UV-B, 280-320 nm) radiation has seriously affected the growth of plants. Finding the technology/method to alleviate the damage of UV-B radiation has become a frontal topic in the field of environmental science. The pretreatment with rare earth elements (REEs) is an effective method, but the regulation mechanism of REEs is unknown. Here, the regulation effects of lanthanum (La(III)) on nitrogen assimilation in soybean seedlings (Glycine max L.) under ultraviolet-B radiation were investigated to elucidate the regulation mechanism of REEs on plants under UV-B radiation. UV-B radiation led to the inhibition in the activities of the key enzymes (nitrate reductase, glutamine synthetase, glutamate synthase) in the nitrogen assimilation, the decrease in the contents of nitrate and soluble proteins, as well as the increase in the content of amino acid in soybean seedlings. The change degree of UV-B radiation at the high level (0.45 W m(-2)) was higher than that of UV-B radiation at the low level (0.15 W m(-2)). The pretreatment with 20 mg L(-1) La(III) could alleviate the effects of UV-B radiation on the activities of nitrate reductase, glutamine synthetase, glutamate synthase, and glutamate dehydrogenase, promoting amino acid conversion and protein synthesis in soybean seedlings. The regulation effect of La(III) under UV-B radiation at the low level was better than that of UV-B radiation at the high level. The results indicated that the pretreatment with 20 mg L(-1) La(III) could alleviate the inhibition of UV-B radiation on nitrogen assimilation in soybean seedlings.

Protective effect of cerium ion against ultraviolet B radiation-induced water stress in soybean seedlings

Effects of cerium ion (Ce(III)) on water relations of soybean seedlings (Glycine max L.) under ultraviolet B radiation (UV-B, 280-320 nm) stress were investigated under laboratory conditions. UV-B radiation not only affected the contents of two osmolytes (proline, soluble sugar) in soybean seedlings, but also inhibited the transpiration in soybean seedlings by decreasing the stomatal density and conductance. The two effects caused the inhibition in the osmotic and metabolic absorption of water, which decreased the water content and the free water/bound water ratio. Obviously, UV-B radiation led to water stress, causing the decrease in the photosynthesis in soybean seedlings. The pretreatment with 20 mg L(-1) Ce(III) could alleviate UV-B-induced water stress by regulating the osmotic and metabolic absorption of water in soybean seedlings. The alleviated effect caused the increase in the photosynthesis and the growth of soybean seedlings. It is one of the protective effect mechanisms of Ce(III) against the UV-B radiation-induced damage to plants.