Zinc-Induced Changes in Morpho-Physiological and Biochemical Parameters in Artemisia annua

Responses of Artemisia annua to different concentrations of zinc [50, 100, 200, 300 and 400 μg g⁻¹(soil dry mass)] were studied during plant ontogeny. Total leaf area, dry mass of leaves, length and dry mass of shoots and roots increased with the age of the plant but the magnitude of increase declined significantly under the influence of Zn treatment. Net photosynthetic rate, intercellular carbon dioxide concentration and stomatal conductance were highest at flowering stage in control and treated plants and decreased at post flowering stage. Contents of chlorophyll a, chlorophyll b, carotenoids, proteins and nitrate reductase activity in leaves increased from pre-flowering to maximum level at flowering stage and decreased thereafter in both control and treated plants. Presence of Zn in the soil drastically decreased/inhibited all the parameters, and the magnitude of decline increased with increasing Zn concentration. This revised version was published online in July 2006 with corrections to the Cover Date.     

驳枝对早花烟草成熟期间叶中叶绿素含量、硝酸还原酶和淀粉酶活性的影响

对早花烟草驳枝后,其成熟期间中部和上部叶中叶绿素（Ch1）含量和硝酸还原酶（NR）活性下降,下部叶则增高,成熟后期的上部叶中淀粉酶（AM）活性明显增强。经驳枝的烟草,中、上部叶烘烤后叶中淀粉、氮和烟碱含量下降,下部叶中的淀粉含量无明显变化。     

Water bird guilds and their feeding connections in the Bodrogzug, Hungary

Thalli of the intertidal Phaeophyte Fucus spiralis L. and the subtidal Chlorophyte Ulva olivascens Dangeard were exposed to artificial UV-A, UV-B and photosynthetically active radiation (PAR) by combination of PAR + UV-A + UV-B (PAB), PAR + UV-A (PA) and PAR (P) treatments. UV-A enhanced photosynthesis and stimulated carbonic anhydrase (CA) and nitrate reductase (NR) in F. spiralis whilst PAR only had an inhibitory effect in this species. U. olivascens suffered chronic photoinhibition in all the treatments as evidenced by reduced maxima photosynthesis (P_max) and photosynthetic efficiency (α). Non stimulatory effect was observed upon CA and NR in this species. Our results showed that artificial UV radiation triggered opposite responses in both species. We suggest that differences shown by both species might be related to their location in the rocky shore and their ability to sense UV. We propose that the ratio UV:PAR acts as an environmental signal involved in the control of photosynthesis as shown by pronounced inhibition in samples exposed to only PAR. We also suggest that UV-regulated photosynthesis would be related to carbon (C) and nitrogen (N) cycles, regulating feedback processes that control C and N assimilation.     

Effect of Temperature on Diurnal Changes in CO2 Exchange in Intact Cucumber Plants

Multifactorial experiments were performed to study the diurnal dynamics of CO₂ exchange in intact cucumber plants (Cucumis sativus L.). Based on experimental data, we analyzed the models of net photosynthesis, night respiration, and biomass accumulation. This analysis allowed us to resolve the growth component of respiration and to determine the diurnal temperature pattern that is optimal for biomass accumulation. It was found that the most profound transformation of assimilates into the biomass occurs under the maximum ratio of growth respiration to maintenance respiration. Under the experimental conditions used, this requirement was fulfilled at a temperature of 25°C during the photoperiod (optimum of net photosynthesis) and at subsequent gradual cooling to a hardening temperature (13°C by the end of the night).     

Effect of sulfur on nitrate reductase and ATP sulfurylase Activities in groundnut (Arachis hypogea L.)

Field experiments were conducted to determine the effect of sulfur (S) and Nitrogen (N) on nitrate reductase (NR) and ATP-sulfurylase activities in groundnut cultivars (Arachis hypogea L. cv. Ambar and Kaushal). Two combinations of S (in kg ha^-1): OS (-S) and 20S (+S) were used with 20 kg ha^-1 N. The application of S enhanced the NR and ATP-sulfurylase activities in both the cultivars at all the growth stages. The application of S also increased soluble protein and chlorophyll content in the all growth stages of both the cultivars. NR and ATP-sulfurylase activities in the leaves were measured at various growth stages as the two enzymes catalyze the rate limiting steps of the assimilatory pathways of nitrate and sulfate, respectively.     

Photosynthetic Efficiency of Plants of Brassica Juncea,Treated with Chlorosubstituted Auxins

The leaves of 29-d-old plants of Brassica juncea Czern & Coss cv. Varuna were sprayed with 10^–6 or 10^–8 M aqueous solutions of indole-3-yl-acetic acid (IAA) or its substituted derivatives 4-Cl-IAA, 7-Cl-IAA, and 4,7-Cl₂-IAA. All the auxins improved the vegetative growth and seed yield at harvest compared with those sprayed with de-ionised water (control). 4-Cl-IAA was most prominent in its effect, generating 21.6, 39.7, 61.0, 35.0, 65.5, and 56.2% higher values for dry mass, leaf chlorophyll content, carbonic anhydrase (E.C. 4.2.1.1) and nitrate reductase (E.C. 1.6.6.1) activities, net photosynthetic rate, and carboxylation efficiency, respectively, in 60-d-old plants. It also enhanced the seed yield by 31.1% over the control. The order of response of the plants to various auxins was 4-Cl IAA 7-Cl IAA > 4,7-Cl₂ IAA = IAA > control.     

The application of ethephon (an ethylene releaser) increases growth, photosynthesis and nitrogen accumulation in mustard (Brassica juncea L.) under high nitrogen levels

Ethephon (2-chloroethyl phosphonic acid), an ethylene-releasing compound, influences growth and photosynthesis of mustard (Brassica juncea L. Czern & Coss.). We show the effect of nitrogen availability on ethylene evolution and how this affects growth, photosynthesis and nitrogen accumulation. Ethylene evolution in the control with low N (100 mg N kg(-1) soil) was two-times higher than with high N (200 mg N kg(-1) soil). The application of 100-400 microl x l(-1) ethephon post-flowering, i.e. 60 days after sowing, on plants receiving low or high N further increased ethylene evolution. Leaf area, relative growth rate (RGR), photosynthesis, leaf nitrate reductase (NR) activity and leaf N reached a maximum with application of 200 microl x l(-1) ethephon and high N. The results suggest that the application of ethephon influences growth, photosynthesis and N accumulation, depending on the amount of nitrogen in the soil.     

羊草和紫花苜蓿生长特征及光合特性对不同土壤水分的响应

采用人工控制实验,对12%(T1)、16%(T2)和20%(T3)3种土壤水分条件下羊草和紫花苜蓿的净光合速率Pn、实际光化学量子效率ФPSⅡ、光化学淬灭q P、非光化学淬灭q N、水分利用效率WUE、株高、分枝分蘖数、生物量等参数进行测定。结果表明,在实验范围内,(1)ФPSⅡ和q P共同影响净光合速率,羊草和紫花苜蓿净光合速率对土壤水分的响应不同,紫花苜蓿的土壤水分生态幅要比羊草窄,羊草生长的最适土壤含水量为20%,随着土壤含水量的降低,净光合速率呈单调递减趋势;紫花苜蓿的最适土壤含水量为16%,其净光合速率与土壤含水量之间呈非线性关系,存在明显阈值。(2)适宜土壤含水量有助于羊草和紫花苜蓿株高和分枝分蘖的生长。(3)在土壤水分低于适宜土壤含水量范围时,羊草和紫花苜蓿有相似的响应机制,都通过增加根系生物量来适应环境胁迫。     

Effect of water deficit on photosynthetic and other physiological responses in grapevine (Vitis vinifera L. cv. Riesling) plants

The grapevine (Vitis vinifera L. cv. Riesling) plants subjected to water deficit were studied for changes in relative water content (RWC), leaf dry mass, contents of chlorophyll (Chl), total leaf proteins, free amino acids, and proline, and activities of ribulose-1,5-bisphosphate carboxylase (RuBPC), nitrate reductase (NR), and protease. In water-stressed plants RWC, leaf dry matter, Chl content, net photosynthetic rate (P _N), and RuBPC and NR activities were significantly decreased. The total leaf protein content also declined with increase in the accumulation of free amino acids. Concurrently, the protease activity in the tissues was also increased. A significant two-fold increase in proline content was recorded.     

土壤酸度对脂松苗木光合和叶绿素荧光的影响

脂松（Pinus resinosa）是北美东北部地区重要的造林树种之一,2004年在我国东北东部山地引种栽培初步获得成功.为扩大脂松栽培范围,采用盆栽方法研究不同土壤酸度（pH分别为4.5、5.5、6.5、7.5和8.0）对脂松苗木光合和叶绿素荧光参数的影响,确定其适生的土壤酸度范围.结果表明：土壤酸度对脂松苗木针叶叶绿素a、b和叶绿素含量、类胡萝卜素含量、净光合速率(P_n)和荧光参数F_o、F_m、F_v、F_v/F_m、Φ_PSⅡ有显著影响（P<0.05）.pH 5.5处理的叶绿素含量和P_n最高,分别比pH 7.5和8.0 处理增加41%、50%和61%、88%;pH 7.5和8.0处理时最低.pH 5.5时叶绿素荧光参数F_v/F_m和Φ_PSⅡ均最高,分别比pH 7.5和8.0处理增加8%、12%和22%、35%;pH 7.5和8.0时则受到明显抑制.土壤pH值为5.5时最适宜脂松生长.     

A method for the determination of nitrate reductase

A procedure for the assay of nitrate reductase based on Szekely's diaminodiphenylsulphone method of nitrate determination (Szekely, E. (1967) Talanta 14, 941–950) is described. The method is simple and sensitive, allowing determination of 1 μg of nitrate in a volume of 1 ml or less. It is particularly suited to the determination of nitrate reductase.     

Cadmium-Induced Changes in Leaf Epidermes, Photosynthetic Rate and Pigment Concentrations in Cajanus Cajan

Application of different concentrations of cadmium [5, 10, 15, 25 and 50 g(CdCl₂) g^–1(soil d.m.)] markedly affected leaves of Cajanus cajan (Linn.) Huth. Due to increased Cd content in leaves, stomatal density and size on abaxial epidermis, and the size of stomatal aperture and length and density of trichomes on both leaf epidermes decreased significantly in the treated plants. Net photosynthetic rate and stomatal conductance were reduced significantly at each concentration of cadmium, whereas reduction in intercellular carbon dioxide concentration was significant at 10 g Cd onwards. The contents of chlorophyll a, chlorophyll b and carotenoids were relatively low during early stages of plant development under the effect of Cd. Nitrate content, nitrate reductase activity and protein content were also lower in treated plants, compared with control.     

Nitrate regulation of nitrate uptake and nitrate reductase expression in barley grown at different nitrate:ammonium ratios at constant relative nitrogen addition rate

Barley (Hordeum vulgare L. cv. Golf) was cultured using the relative addition rate technique, where nitrogen is added in a fixed relation to the nitrogen already bound in biomass. The relative rate of total nitrogen addition was 0.09 day^?1 (growth limiting by 35%), while the nitrate addition was varied by means of different nitrate: ammonium ratios. In 3- to 4-week-old plants, these ratios of nitrate to ammonium supported nitrate fluxes ranging from 0 to 22 μmol g^?1 root dry weight h^?1, whereas the total N flux was 21.8 ± 0.25 μmol g^?1 root dry weight h^?1 for all treatments. The external nitrate concentrations varied between 0.18 and 1.5 μM. The relative growth rate, root to total biomass dry weight ratios, as well as Kjeldahl nitrogen in roots and shoots were unaffected by the nitrate:ammonium ratio. Tissue nitrate concentration in roots were comparable in all treatments. Shoot nitrate concentration increased with increasing nitrate supply, indicating increased translocation of nitrate to the shoot. The apparent V_max for net nitrate uptake increased with increased nitrate fluxes. Uptake activity was recorded also after growth at zero nitrate addition. This activity may have been induced by the small, but detectable, nitrate concentration in the medium under these conditions. In contrast, nitrate reductase (NR) activity in roots was unaffected by different nitrate fluxes, whereas NR activity in the shoot increased with increased nitrate supply. NR-mRNA was detected in roots from all cultures and showed no significant response to the nitrate flux, corroborating the data for NR activity. The data show that an extremely low amount of nitrate is required to elicit expression of NR and uptake activity. However, the uptake system and root NR respond differentially to increased nitrate flux at constant total N nutrition. It appears that root NR expression under these conditions is additionally controlled by factors related to the total N flux or the internal N status of the root and/or plant. The method used in this study may facilitate separation of nitrate-specific responses from the nutritional effect of nitrate.     

ISOLATION AND PARTIAL CHARACTERIZATION OF NITRATE ASSIMILATION MUTANTS OF DUNALIELLA TERTIOLECTA (CHLOROPHYCEAE)1

Fifteen nitrate assimilation-deficient mutants of the euryhaline green alga, Dunaliella tertiolecta Butcher were selected by their chlorate resistance. Ten mutants, unable to grow on NO₃^? but able to grow on NO₂^?, had no detectable nitrate reductase activity. Five mutants, unable to grow on either NO₃^? or NO₂^?, had depressed levels of both nitrate and nitrite reductase. A method for assaying methyl viologen-nitrate reductase in the presence of nitrite reductase is described.