Dependence of starch storage on nutrient availability and photon flux density in small birch Betula pendula Roth)

Abstract Small birch plants (Betula pendula Roth) were grown in a climate chamber at different levels of nutrient availability and at two photon flux densities. The extent to which starch storage was dependent upon nutrient availability and photon flux density was investigated. Acclimated values of starch concentration in leaves were highest at low nutrient availability and high photon flux density. Starch storage in roots was only found at the lowest nutrient availability. However, the relative rate of starch storage (starch stored per unit plant dry weight and time) was higher in plants with good nutrition. The data suggest that, at sub-optimal nutrient availability, the momentary rate of net shoot photosynthesis is unlikely to limit the structural (as opposed to carbon storage) growth of the plant. Although photosynthetic rate per unit leaf area (as measured at the growth climate) was slightly lower in plants with poor nutrient availability, photosynthetic rate per unit leaf nitrogen was higher. These data suggest a priority of leaf nitrogen usage in photosynthesis, with limiting amounts of leaf nitrogen (and possibly other nutrients) for subsequent growth processes. This argument is consistent with the higher concentrations of starch found in plants with poor nutrient availability.     

Translocation of radionuclides of Co, Zn, Se, Rb, Y, Tc, and Re into organs of tomato plant via roots

The translocation of the radionuclides of Co, Zn, Se, Rb, Y, Tc, and Re into red and green fruits, flesh, seeds, rind, calyxes, flower, leaves, and stems via the root of the tomato plant at two different growth stages was studied by a multitracer technique. The contents (%/g) of Co, Zn, Se, and Y in the roots were the highest among the organs, but only small amounts of them were translocated into the aerial parts after 5 d cultivation with a multitracer. In contrast, Rb, Tc, and Re showed rapid translocation into the stems and leaves from the root. In the plants cultivated for 95 d with a multitracer, Zn, Se, and Rb distributed in all of the organs, Co in the organs except for flowers, and Y, Tc, and Re in the limited organs. The translocation ratio of the elements for the edible part of the plants cultivated for 95 d decreased in the order of Rb>Zn>Co≈Se>Tc≈Y>Re. The transfer factor of the elements for tomato fruit was determined to be in the range of 10⁻⁵–10⁻². The characteristic translocation behavior of the elements gives us fundamental information on the assessment of pollutant uptake by the tomato plant.     

Interactions between selenium and iodine uptake by spinach (Spinacia oleracea L.) in solution culture

Interactions between Se (as selenate) and I (as iodate) uptake by spinach plants (Spinacia oleracea L.) were studied under controlled conditions using solution culture. Spinach readily accumulated both Se and I in the edible parts, the leaves, with solution-to-leaf transfer factors ranging from 3.5 to 13.4. The distribution coefficients between leaves and roots ranged from 4.07 to 5.66 for I and 4.51 to 8.59 for Se. Selenium concentrations in plant tissues were unaffected by addition of I to the nutrient solution. Similarly, plant I concentrations were unaffected by addition of Se to the nutrient solution, except in nutrient solution with I at a concentration of 50 μM, in which addition of Se lowered shoot I concentrations significantly, but the effect was of low magnitude. These results indicate the possible feasibility of dual supplementation of plant growth substrates with Se and I to improve human nutrition where these two elements are deficient in the diet. The data also indicate the involvement of a positive feedback mechanism in the uptake of Se by spinach plants, since Se concentrations in leaves increased disproportionately with increasing Se concentration in the nutrient solution.     

盐胁迫下荒漠共生植物红砂与珍珠的根茎叶中离子吸收与分配特征

西北荒漠地区C3小灌木红砂(Reaumuria soongorica)和C4半灌木珍珠猪毛菜(Salsola passerina)在特定环境下混生在一起,分布面积广阔。以采自腾格里沙漠边缘荒漠地带的天然野生珍珠猪毛菜和红砂群落的幼苗为材料,经0、100、200、300、400mmol/L NaCl盐溶液共同胁迫10 d,检测它们的含水量、主要矿质离子在根茎叶的含量与分布,揭示二者耐盐的共生协同的离子平衡适应机制。试验结果发现,珍珠猪毛菜叶片具有"吸钾排钠的"的耐盐特征,红砂叶片具备"吸钠排钾"的特征,吸收利用无机矿质离子具备互补效应。二者耐盐Cl、Ca和Si离子吸收与累积能力存在很大差异:随着盐胁迫程度加剧,红砂的根茎叶中Cl离子含量持续增加,并且为珍珠猪毛菜的2—5倍;珍珠猪毛菜根中Ca离子含量为红砂的2—3倍,但含量变化不显著;红砂根中Si离子含量迅速降低后稳定,并且是珍珠猪毛菜根的3—5倍,其他器官变化差异较小。因此,红砂与珍珠猪毛菜的共培养盐胁迫下根中吸收的离子侧重不同,红砂以Na、Cl、Si为主,珍珠猪毛菜以K、Ca为主。随着盐胁迫的程度加强,离子选择吸收系数S k,Na的变化趋势降低,表明二者叶部对Na的选择性减小,K的选择性吸收积累增大,增强了它们的抗盐性,最终使叶片所受盐害减小。总之红砂与珍珠猪毛菜共生的耐盐离子稳态机制显著不同,离子吸收与分布具有互补互利的效应。     

不同产地黄芩中无机元素含量及其与根际土壤无机元素的关系

药用植物中各无机元素含量的不仅影响药用植物的生长发育,也是药材有效成分的构成因子。通过对全国范围内16个不同产地(即居群)的92个野生黄芩(Scutellaria baicalensis Georgi)样本及其相应的根际土壤中10种无机元素含量的分析,发现不同产地黄芩及其根际土壤无机元素都有很大变异,且不同产地黄芩根际土壤中无机元素的变异远大于黄芩药材中无机元素的变异。总体来看,黄芩中Mg(9级)含量较其他植物含量高;P(1级)、K(2级)、Mn(3级)含量与其他植物相比处处较低水平;黄芩对Sr(富集系数达到3.52)有较强富集。并且通过无机元素分布曲线分析建立了无机元素指纹谱,主成分分析筛选出黄芩主要特征无机元素为Mg、K、Ca、Fe、Zn。本研究还表明,黄芩对各元素的吸收能力受产地的影响较大,提示黄芩对无机元素的吸收与各产地根际土壤无机元素有一定关联性。     

The effect of calcium bicarbonate on iron absorption and distribution byChrysanthemum morifolium, (Ram.)

Summary Plants grown for two weeks in high-bicarbonate nutrient solution with iron became chlorotic, absorbed less iron, and translocated a lower percentage of absorbed iron than did green plants grown under low bicarbonate with iron. Chlorotic plants, pretreated in low-bicarbonate solutions lacking iron, absorbed more iron and translocated a higher percentage to leaves than the green plants. Plants induced to chlorosis by high bicarbonate absorbed less iron after transfer to low-bicarbonate solution containing iron than did chlorotic plants pretreated with low-carbonate solution lacking iron. Initial localization of iron occurred in the roots. A considerable amount of the iron initially found on the roots was translocated to developing shoots over a nine-week period unless the plants were grown in high bicarbonate solutions. More iron was translocated from roots of plants in minus-iron solutions following initial absorption than when iron was supplied in the nutrient solutions. Journal Series Paper736. University of Georgia, College of Agriculture Experiment Stations, College Station, Athens, Ga. 30601.     

Stomatal conductance of differentially salinized plants

Stomatal resistance was measured daily with a stomatal diffusion porometer during a 4-week period in leaves of bean (Phaseolus vulgaris L., var. Bush Blue Lake) and barley (Hordeum vulgare L., var. Liberty) plants having roots equally split between two differentially salinized nutrient solutions. The stomatal conductance (reciprocal of stomatal resistance) of plants with half their roots in saline solutions was intermediate between the stomatal conductances of plants grown in nonsaline solutions and those grown in saline solutions.     

Leaf water potential of differentially salinized plants

Water and osmotic potential energies were measured with thermocouple psychrometers, at intervals during a 4-week period, in growing leaves of bean (Phaseolus vulgaris, var. Blue Lake) and barley (Hordeum vulgare, var. Liberty) plants having roots equally split between 2 differentially salinized nutrient solutions. The osmotic potentials of plants with half their roots in saline solutions were about halfway between the osmotic potentials of plants grown in nonsaline solutions and those grown in saline solutions. By the end of the 4-week measurement period, the beans and barley were almost mature. The final dry weights of shoots of plants with half their roots in saline solutions were about halfway between the dry weights of the shoots of plants grown in nonsaline solutions and the dry weights of those in saline solutions. The results obtained showed that the degree of osmotic adjustment and the rate of growth were functions of the proportion of the root system exposed to saline conditions.     

Calcium and Salt Toleration by Bean Plants

The role of calcium in the salt relations of the bean plant, Phaseolus vulgaris, was examined. Brittle wax bush bean plants were cultured in nutrient solutions containing 50 mM NaCl. In the absence of added calcium the plants showed a general breakdown of the roots. A low concentration of calcium in the nutrient solution (0.1 mM) prevented this. Without added calcium the plants absorbed and translocated sodium at such a rate that high concentrations of it built up in the leaves within two days. With increasing concentrations of calcium in the nutrient solution the leaves contained progressively less sodium, and at 3 mM CaSO₄ the concentrations of sodium in the leaves was equal to that of the control plants grown without addition of salt. Even after both roots and stems had reached a high concentration of sodium, the leaves of plants grown in the presence of adequate concentrations of calcium contained little sodium.     

Aspects of phytoremediation for chromium contaminated sites using common plants Urtica dioica, Brassica napus and Zea mays

As chromium is widely used in many industries of which leather industries are the biggest consumers, wastes from tanneries pose a serious threat to the environment. Present research conducted greenhouse pot experiments on several plants using different solutions to find out their phytoextraction potential. Among the plants, Urtica dioica found to be very effective due to its higher uptake capacity for chromium. The analyses showed that with 500 mg/l solutions Cr concentration in roots was 38.9% higher (average 20 mg/kg) than plants fed with 200 mg/l solutions (phytostabilisation), while with 200 mg/l solutions more Cr was transported to leaves (phytoextraction), 10.52% higher (average 9.5 mg/kg) concentration than plants fed with 500 mg/l solutions, but also means that plants were less affected by toxicity. Zea mays showed high tolerance towards Cr with negligible concentration in leaves. Although average Cr concentration in Brassica napus is lower (25% and 21% for 200 mg/l and 500 mg/l solutions respectively) than Urtica dioica which still could account for phytoextraction, but due to its high vulnerability to insects its potentiality has downgraded. Among other elements, K being a component of the salt, played significant role for plants growth and survival—opening new avenue for phytoremediation of contaminated sites.     

Proline involvement in the common sage antioxidant system in the presence of NaCl and paraquat

To elucidate proline antioxidant properties in common sage (Salvia officinalis L.) plants, they were treated with paraquat (a producer of superoxide radical) and/or NaCl and also with paraquat and proline at the stage of 4–5 true leaves. The paraquat solution (1 ml containing 0.1 μmol of the agent) was applied to the leaf surface; NaCl (200 mM) and proline (the final concentration of 5 mM) were added to nutrient medium. Experimental plants were firstly kept in darkness for 12 h, then illuminated, and in 3, 6, and 12 h, leaves and roots were fixed for biochemical analyses. The results obtained are in agreement with the supposition of proline antioxidant properties. In particular, it was established that paraquat induced a slight increase in the proline level in the leaves during dark period of plant growth and also during subsequent 3 h after light switching on. This transient proline accumulation in the leaves was accompanied by its level decrease in the roots. Proline addition to the nutrient medium of paraquat-treated plants neutralized paraquat damaging action on the leaves. In the presence of paraquat, proline treatment reduced the accumulation in the roots of hydrogen peroxide and malondialdehyde, the product of membrane lipid peroxidation. It also affected indirectly the activities of superoxide dismutase (SOD) and free, covalently bound, and ionically bound peroxidases. Keeping in mind that, in the presence of paraquat, superoxide-induced changes in SOD activity in the roots were negatively correlated with the level of proline, which content was the highest during the last hours of experiments, we can conclude that proline antioxidant effects are manifested only after 12 h of stressor action, whereas antioxidant enzymes are involved in ROS scavenging during the earlier stage of damaging factor action.     

Contrasting silicon uptakes by coniferous trees: a hydroponic experiment on young seedlings

Silicon uptake by terrestrial plants impacts the Si land-ocean fluxes, therefore inducing significant modifications for biogeochemical cycle of Si. Understanding the mechanisms that control Si uptakes by forest vegetation is of great interest for the study of the global Si cycle as the world’s total forest area corresponds to about 30% of the land area. Our study compares Si uptake in controlled conditions by two coniferous species (Pseudotsuga menziensii and Pinus nigra) exhibiting contrasting Si uptake in the field. For this purpose, seedlings were grown for 11 weeks under controlled conditions in hydroponics with different Si concentrations (0.2 to 1.6 mM) in nutrient solutions. The Si concentrations were greater in Douglas fir leaves as compared with Black pine leaves and increased, depending on the Si concentration in the nutrient solution. According to mass balance, Si absorption seems to have been driven by passive Si transport at 0.2 mM Si (realistic concentration for forest soil solutions) and was rejective at higher Si concentrations in nutrient solution for both species. For this reason, we attributed the higher Si concentration in Douglas fir leaves to the greater cumulative transpiration of these seedlings. We suggest that contrasting transpiration rates may also play a key role in controlling Si accumulation in leaves at field scale.     

Physiological Characteristics of Fe Accumulation in the ;Bronze' Mutant of Pisum sativum L., cv ;Sparkle' E107 (brz brz)

The pea (Pisum sativum L.) mutant, E107 (brz, brz) accumulated extremely high concentrations of Fe in its older leaves when grown in light rooms in either defined nutrient media or potting mix, or outdoors in soil. Leaf symptoms (bronze color and necrosis) were correlated with very high Fe concentrations. When E107 plants were grown in nutrient solutions supplied 10 μm Fe, as the Fe(III)-N,N′-ethylenebis[2-(2-hydroxyphenyl)glycine] chelate, their roots released higher concentrations of Fe(III) reducing substances to the nutrient media than did roots of the normal parent cv, `Sparkle.' Reciprocal grafting experiments demonstrated that the high concentrations of Fe in the shoot was controlled by the genotype of the root. In short-term <sup>59</sup>Fe uptake studies, 15-day-old E107 seedlings exhibited higher rates of Fe absorption than did `Sparkle' seedlings under Fe-adequate growth conditions. Iron deficiency induced accelerated short-term Fe absorption rates in both mutant and normal genotypes. Iron-treated E107 roots also released larger amounts of both protons and Fe(III) reductants into their nutrient media than did iron-treated `Sparkle' roots. Furthermore, the mutant translocated proportionately more Fe to its shoot than did the parent regardless of Fe status.     

Effect of soil flooding on photosynthesis,carbohydrate partitioning and nutrient uptake in the invasive exotic Lepidium latifolium

Lepidium latifolium L. is an invasive exotic crucifer that has spread explosively in wetlands and riparian areas of the western United States. To understand the ecophysiological characteristics of L. latifolium that affect its ability to invade riparian areas and wetlands, we examined photosynthesis, chlorophyll concentration, carbohydrate partitioning and nutrient uptake in L. latifolium in response to soil flooding. Photosynthesis of flooded plants was about 60–70% of the rate of unflooded controls. Chlorophyll concentrations of flooded plants were about 60–70% of the unflooded plants during 15–50 days of flooding. Flooding resulted in an increase in leaf starch concentration, but root starch concentration was not significantly affected. However, concentrations of soluble sugar were significantly higher in both leaves and roots of flooded plants than unflooded controls. On day 50 after initial flooding, the concentrations of N, P, K and Zn in leaves of flooded plants were lower than in control plants. The concentrations of Mn and Fe in leaves of flooded plants were eight and two times those of control plants, respectively. In contrast, N, P, K and Zn concentrations of roots of flooded plants were slightly higher than in unflooded plants. The concentrations of Fe and Mn in roots of flooded plants were 15 and 150 times those of the control plants, respectively. The transport of P, K, and Zn to shoots decreased and that of Mn increased under flooding. The accumulation of N, K and Zn in roots decreased and that of Mn increased in response to flooding. The results suggested that the maintenance of relatively high photosynthesis and the accumulation of soluble sugar in roots of flooded plants are important adaptations for this species in flooded environments. Despite a reduction in photosynthesis and disruption in nutrient and photosynthate allocation in response to flooding, L. latifolium was able to survive 50 days of flooding stress. Overall, L. latifolium performed like a facultative hydrophyte species under flooding.     

Maize growth and ion absorption in Richter's solution at different flow rates

By comparing maize plants cultivated in standing nutrient solution with those from solutions flowing at different flow rates it has been established that absorption of nitrogen, potassium and especially of phosphorus was increased owing to the flow. There was likewise a relative rise in the distribution of nutrients to the overground parts of the plants. The content expressed per unit dry matter was increased only in the case of phosphorus; with nitrogen and potassium it was slightly lower than in the standing solution. Increasing amounts of iron were required under the conditions of flowing nutrient solutions to prevent chlorosis of the plants. The production of dry matter,NAR andRGR was also increased because of the flow. The flow considerably changed the habitus of the primary roots of the maize plants. The roots were longer, thinner and on the whole they contained relatively less dry matter (RWR). The lengthening of the roots is explained as a response to stimulation by the solution flow—the rheotropism.     

Absorption of Nitrogen, Phosphorus, and Potassium from Nutrient Sprays by Leaves

Barley, Brussels sprout, French bean, tomato, and sugar-beetplants grown in soil in pots and sprayed, usually daily, forseveral weeks, with nutrient solutions containing nitrogen,phosphorus, potassium, and a spreader, with precautions to preventthe spray solution falling on the soil, had higher nutrientcontents and dry weights than control plants sprayed with waterand spreader only. Increase in nutrient content occurred withhigh or low levels of nutrient supply to the roots and was approximatelyproportional to the concentration of spray and to the frequencyof spraying. The nitrogen content of sugar-beet plants was increased equallyby spraying with solutions supplying ammonium sulphate, calciumnitrate, or urea in equivalent concentrations. Nutrient uptake from solutions sprayed on leaves influenceduptake by the roots so that the additional amounts of nutrientcontained in sprayed plants may be greater or smaller than theamount absorbed from the spray by the leaves.     

A Method for Characterizing the Relation between Nutrient Concentration and Flux into Roots of Intact Plants

A method based on the rate of depletion of a nutrient from solution was developed to characterize nutrient flux of plant roots. Nutrient concentration of the solution was measured at a series of time intervals to describe the complete depletion curve. An integrated rate equation, based on a Michaelis-Menten model, was developed and fit to the data of the depletion curve using a least-square procedure. The equation contained values for V_max, the maximum rate of influx; Km, the Michaelis constant; and E, efflux, which were used to describe the relation between solution concentration and net influx rate. Models other than Michaelis-Menten could also be used. The method uses only one plant or group of plants to obtain data over a range of nutrient concentrations, is adapted particularly to the low concentration range, and measures the concentration below which net influx ceases. With this method the plant is in steady state absorption prior to the experiment and continues at this steady state until near the end of the experiment.     

西北干旱区荒漠植物叶片和细根碳、氮、磷化学计量特征

植物的叶片和细根是植物地上部分和地下部分最重要的营养器官,其碳(C)、氮(N)、磷(P)化学计量特征反映了植物的养分限制状况及叶片与细根间的协同作用,开展叶片与细根化学计量关系的研究,对认识植物养分利用策略及元素间平衡关系有重要意义。对西北干旱区21种荒漠植物叶片与细根C、N、P含量进行了测定,分析了C、N、P含量及其计量比在不同生活型及不同器官间的关系。结果表明:1)西北干旱区荒漠植物叶片与细根C含量相对稳定,叶N、P含量高于细根,说明在干旱生境中,植物对养分的分配侧重于地上部分,以完成其正常的生命活动;叶片与细根的N ∶ P无显著差异,有明显的保守性,表明植物地上与地下部分养分吸收策略与分配规律具有一致性;2)不同生活型植物叶片和细根的C、N、P含量及C ∶ N、C ∶ P存在显著差异,灌木与禾草具有较高的C ∶ N和C ∶ P,杂类草具有较高的N、P含量,说明灌木与禾草倾向于保守型养分适应策略,杂类草倾向于快速生长的资源竞争策略;3)21种荒漠植物叶片与细根N、P含量间均存在显著的正相关关系,表明西北干旱区荒漠植物体内N、P元素间存在相互作用;4)植物叶片与细根间C、N、P含量及C ∶ N、C ∶ P存在等速生长关系,表明植物光合产物和养分在地上与地下部分间的分配具有平行的比例关系,但这种关系受生活型影响。上述结果表明西北干旱区不同生活型植物在恶劣生境中存在不同的养分适应策略,且地上与地下部分的养分利用策略及分配规律存在协同作用,这为进一步认识西北干旱区荒漠植物的养分利用策略提供了试验基础。     

Effect of Nitrate and Ammonium Nutrition of Nonnodulated Phaseolus vulgaris L. on Phosphoenolpyruvate Carboxylase and Pyruvate Kinase Activity

Young bean plants (Phaseolus vulgaris L. var Saxa) were fed with 3.5 or 10 millimolar N in either the form of NO₃⁻ or NH₄⁺, after being grown on N-free nutrient solution for 8 days. The pH of the nutrient solutions was either 6 or 4. The cell sap pH and the extractable activities of phosphoenolpyruvate carboxylase and of pyruvate kinase from roots and primary leaves were measured over several days.

The extractable activity of phosphoenolpyruvate carboxylase (based on soluble protein) from primary leaves increased with NO₃⁻ nutrition, whereas with NH₄⁺ nutrition and on N-free nutrient solution the activity remained at a low level. Phosphoenopyruvate carboxylase activity from the roots of NH₄⁺-fed plants at pH 4 was finally somewhat higher than from the roots of plants grown on NO₃⁻ at the same pH. There was no difference in activity from the root between the N treatments when pH in the nutrient solutions was 6. The extractable activity of pyruvate kinase from roots and primary leaves seemed not to be influenced by the N nutrition of the plants.

The results are discussed in relation to the physiological function of both enzymes with special regard to the postulated functions of phosphoenolpyruvate carboxylase in C3 plants as an anaplerotic enzyme and as part of a cellular pH stat.

     

Changes in the concentration of phenolic compounds and exudation induced by phosphate deficiency in bean plants (Phaseolus vulgaris L.)

The effect of prolonged phosphate starvation of bean plants (Phaseolus vulgaris L.) on the concentration of phenolics and their exudation by roots was studied. Plants cultured on phosphate-deficient media maintained a steady concentration of total phenolics in the leaves, whereas in the leaves of plants grown on complete nutrient media the phenolic concentration decreased. After 18 days of culture, higher total phenolics and anthocyanin concentrations in phosphate-deficient leaves compared with control leaves were observed. The divergent trends in total phenolic concentrations between phosphate-deficient and control leaves corresponded to the changes in the activity of L-phenylalanine ammonia-lyase. In the roots, the concentration of total phenolics was lower in phosphate-deficient plants compared with control plants. However, after 18 days of culture of bean plants, the amount of exuded phenolics from phosphate-deficient roots was 5-times higher than that from the roots of control plants. The activity of L-phenylalanine ammonia-lyase was twice as high in the roots of phosphate-starved plants. Comparable rates in the exudation of phenolics by bean roots observed after 18 days of culture on nitrogen-deficient or phosphate-deficient medium may suggest a similar system of signal transduction for phenolics release. The results are discussed in relation to the possible functions of phenolics in nutrient uptake and as chemical signals in root-soil microbe interactions to enhance the plant adaptation to particular environmental conditions.