Effects of lanthanum(Ⅲ) on nitrogen metabolism of soybean seedlings under elevated UV-B radiation

The hydroponic culture experiments of soybean bean seedlings were conducted to investigate the effect of lanthanum （La） on nitrogen metabolism under two different levels of elevated UV-B radiation （UV-B, 280-320 nm）. The whole process of nitrogen metabolism involves uptake and transport of nitrate, nitrate assimilation, ammonium assimilation, amino acid biosynthesis, and protein synthesis. Compared with the control, UV-B radiation with the intensity of low level 0.15 W/m^2 and high level 0.45 W/m^2 significantly affected the whole nitrogen metabolism in soybean seedlings （p 〈 0.05）. It restricted uptake and transport of NO3^-, inhibited activity of some key nitrogen-metabolism-related enzymes, such as： nitrate reductase （NR） to the nitrate reduction, glutamine systhetase （GS） and glutamine synthase （GOGAT） to the ammonia assimilation, while it increased the content of free amino acids and decreased that of soluble protein as well. The damage effect of high level of UV-B radiation on nitrogen metabolism was greater than that of low level. And UV-B radiation promoted the activity of the anti-adversity enzyme glutamate dehydrogenase （GDH）, which reduced the toxicity of excess ammonia in plant. After pretreatment with the optimum concentration of La （20 mg/L）, La could increase the activity of NR, GS, GOGAT, and GDH, and ammonia assimilation, but decrease nitrate and ammonia accumulation. In conclusion, La could relieve the damage effect of UV-B radiation on plant by regulating nitrogen metabolism process, and its alleviating effect under low level was better than that under the high one.

Effect of Lanthanum (Ⅲ) on Reactive Oxygen Metabolism of Soybean Seedlings under Supplemental UV-B Irradiation

The effect of lanthanum （Ⅲ） on reactive oxygen metabolism of soybean seedlings under elevated ultraviolet-B radiation（UV-B：280~320 nm）at 0.15 and 0.45 W·cm-2 levels respectively was studied through hydroponics in the laboratory.Plasmolemma permeability and contents of malonadialdehyde（MDA）,hydrogen peroxide（H2O2）,and proline gradually increased during the imposition of UV-B radiation and subsequently decreased during recovery from UV-B stress.The dynamic tendency of catalase（CAT）activity was similar to that of the above four indices.The activity of peroxidase（POD）initially increased,then remained at a high level,and finally dropped steeply when soybean seedlings were exposed to a low dosage of UV-B radiation.However,POD activity rose throughout and declined slightly on the eleventh day when soybean seedlings were stressed by a high dosage.With the addition of La （Ⅲ） of 20 mg·L-1,the rising tendency of plasmolemma permeability and contents of MDA,H2O2,and proline were slowed down during the stress period,whereas the declining speed was accelerated during the recovery period.The activities of CAT and POD were higher than those without La （Ⅲ） in all experiments.It suggested that the regulative effect of La （Ⅲ） on antioxidant enzymes such as CAT and POD could strengthen their capacities to scavenge reactive oxygen species（ROS）,decrease contents of MDA and proline,and maintain normal plasmolemma permeability.Further more,the protective potential of La （Ⅲ） was better under low UV-B radiation than under a high one.

Effect of Lanthanum on Plants under Supplementary Ultraviolet-B Radiation: Effect of Lanthanum on Flavonoid Contents in Soybean Seedlings Exposed to Supplementary Ultraviolet-B Radiation

The effect of La on flavonoids, chlorophyll contents, and phenylalanine ammonia-lyase （PAL） activity in soybean seedlings under supplementary ultraviolet-B radiation （UV-B, 280 - 320 nm） was studied. The results show that PAL activity, contents of flavonoids and chlorophyll in the plants pretreated with La （20 mg·L^- 1 ） are higher than those in CK. UV-B radiation could result in an increase in flavonoid content and PAL activity, associated with a decrease in chlorophyll content. However, the increase in the range of PAL activity and flavonoid content in UV-B treatment are lesser than those in the La treatment. The changes of flavonoid contents and PAL activity in La ＋ UV-B treatment are similar to those in UV-B treatment, and the increase in their range is higher than those in UV-B treatment. This shows that La can enhance the resistance of soybean seedling to UV-B radiation and alleviate the damage of UV-B radiation by increasing flavonoid content, chlorophyll content, and PAL activity.

Ecophysiological Effect of La-Gly on Soybean Harmed by Acid Rain

Spraying soybean seedlings with 30 mg·L -1 La-Gly apparently reduces the harm of pH 2 5 acid rain to the plants. The results show that this is related to many physiological reactions, for example the La-Gly increases both the photosynthetic rate and chlorophyll content, decreases the content of malond ialdehyde, reduces the cell membrane permeability, and keeps the stability of pH value and triphenyl tetrazolium chloride reduction ability of the cell juice of soybean seedlings etc.

Effects of drought stress on photosynthesis and chlorophyll fluorescence images of soybean(Glycine max)seedlings

The main purpose of this research is to provide a theoretical foundation for the screening of drought-resistant soybean varieties and to establish an efficient method to detect the PSII actual photochemical quantum yields efficiently.Three soybean varieties were compared in this experiment after 15 d when they were planted in a greenhouse.These varieties were then exposed to light drought stress(LD)and serious drought stress(SD)conditions.With five times’measurement,chlorophyll fluorescence and soil-plant analysis development considered as the main basis for this study.Several parameters in SD conditions significantly reduced,such as net photosynthetic rates(Pn),stomatal conductance(Gs),PSII primary light energy conversion efficiency(Fv/FM),PSII actual photochemical quantum yields[Y(II)],photochemical quenching coefficient(qP)and non-photochemical quenching coefficient(qN).The soybeans in the seedling stage adapted to the inhibitory effect of drought stress on photosynthesis through stomatal limitation.Under serious drought stress,non-stomatal limitation damaged the plant photosynthetic system.The amplitudes of Pn and Y(II)of drought-resistant Qihuang 35 were lower than those of the two other varieties.Based on the data of this study,a new method had been developed to detect Y(II)which reflected the photosynthetic capacity of plant,R=0.85989,u=0.048803 when using multiple linear regression,and R=0.84285,u=0.054739 when using partial least square regression.