Content Of Seedlings Research Articles

Effect of wood ash application on the morphological, physiological and biochemical parameters of Brassica napus L.

The present study was conducted to determine the effect of wood ash application on different parameters of Brassica napus L. including seed germination, seedling growth, fresh and dry biomass, water content in seedlings, photosynthetic pigments, soluble sugars, total protein and cell viability. In addition, the effect of wood ash on soil microflora and accumulation of trace elements in seedlings were determined. The seeds of B. napus were grown at different doses of wood ash (0, 1, 10, 25, 50 and 100 g (wood ash)/kg (soil)) and the effect on various parameters was determined. Wood ash significantly inhibited seed germination at doses above 25 g/kg and there was no germination at 100 g/kg of wood ash. At lower concentrations of wood ash, most of the growth parameters of seedlings were stimulated, but at higher concentrations of wood ash most of the studied parameters were adversely affected. Wood ash was found to be very detrimental to B. napus when applied above 25 g/kg. Wood ash application resulted in an increased bioaccumulation of trace elements in seedlings of B. napus. Almost all trace elements were significantly higher in seedlings grown in wood ash above 10 g/kg as compared to the control. An increase in total microbial count was observed with wood ash treatment which was statistically significant at 1 and 10 g/kg of wood ash. It is concluded that at very high concentration, wood ash can be detrimental to plants; however, its application at lower application rate can be recommended.

Comparative responses of two Trigonella species to salinity and drought stresses in vitro

Effects of salinity and drought on growth, contents of proline, malondialdehyde (MDA), proteinand activity of antioxidative enzymes were studied in two Trigonella species. Seeds andexplants of T. foenum-graecum and T. aphanoneura were grown on Murashige and Skoogmedium (MS) complemented with iso-osmotic concentrations of NaCl (0, 100, 150 mM) andmannitol (0, 180, 275 mM). Growth and relative water content (RWC) of seedlings and callidecreased by increasing of salinity and drought in both species. In contrast to that of calli,proline and protein contents increased in seedlings of both species under both stresses. Theincrease of proline content in seedlings of T. aphanoneura was higher than that of T. foenumgraecumunder NaCl stress. MDA content in seedlings of T. aphanoneura was higher than thatof T. foenum-graecum and increased in both species under salinity. Among antioxidativeenzymes, catalase (CAT) activity increased continuously in seedlings of T. aphanoneuracomparing to that of T. foenum-graecum. Similar increasing trends were obtained regardingCAT activities in calli of both species under both stresses. Increase in activities of SOD, CATand POX was observed in calli of both species under stress. It seems that undifferentiated callirespond more regularly to both stresses. Finally, higher proline content and lower amount ofMDA could be considered as criteria for higher tolerance of T. foenum-graecum seedlingsagainst osmotic stresses.

Antioxidant enzyme activity and osmolyte content in winter cereal seedlings under hardening and cryostress

Activities of antioxidant enzymes and the osmolyte contents in seedlings of winter rye (Secale cereale L.), soft (Triticum aestivum L.) and durum (T. durum L.) wheat, and barley (Hordeum vulgare L.) grown at 20°C (control) or after 7-day cold hardening at 2°C and/or 5-hour freezing at −6°C were investigated. It was found that nonhardened rye seedlings differed from those of other cereals by their ability to survival after freezing at −6°C and higher activity of guaiacol peroxidase (GPO) and high content of proline. Hardening induced the increase in the frost tolerance of all cereals under study, and the resistance of rye and soft wheat was found to be significantly higher than that of durum wheat and barley. Rye and soft wheat exhibited more profound tolerance to oxidative damages as well, and it was expressed in lesser increase in the MDA content after freezing. In the course of hardening, detectable increase in the activities of GPO and catalase (CAT), as well as the contents of proline and soluble carbohydrates, was observed in seedlings of all cereals under study. In barley, the activity of superoxide dismutase (SOD) increased to the highest extent under these conditions. After freezing of both hardened and nonhardened seedlings, higher activities of all tested antioxidant enzymes were revealed in rye and soft wheat as compared to those in durum wheat and barley. In this case, hardened rye and soft wheat seedlings after freezing displayed increased content of proline. All these results lead to the conclusion that the high content of proline and activity of GPO observed in rye seedlings may determine their increased constitutive frost tolerance, whereas high tolerance of hardened soft wheat seedlings is primarily associated with accumulation of low-molecular-weight protectors, such as sugars and proline, and, to some extent, with the increased activity of antioxidant enzymes.

Influência da acidez e do teor de fósforo do solo no crescimento inicial do mogno

<p class="Default"><span>A adubação fosfatada para espécies perenes nativas necessita de estudos, tanto em condições de campo, como na fase de mudas. No presente estudo, objetivou-se avaliar a interação entre calagem e níveis de fósforo no crescimento inicial e o acúmulo de nutrientes do mogno (<em>Swietenia macrophylla </em>King.), cultivado num Latossolo Amarelo Distrófico típico em casa de vegetação. O delineamento experimental utilizado foi o inteiramente casualizado em esquema fatorial, com três repetições. Os tratamentos foram constituídos de seis doses de P (11; 22; 44; 66; 88 e 110 mg dm</span><span class="A9"><sup><span>-3</span></sup></span><span>), além do tratamento controle (sem a aplicação de P), combinadas com a aplicação de 500 mg dm</span><span class="A9"><span>-3 </span></span><span>de calcário ou sem a adição do corretivo. A adição de doses crescentes de P com aplicação de calcário favoreceram o crescimento inicial e o acúmulo de nutrientes em mudas de mogno, todavia, sem apresentar interações entre si. A máxima eficiência econômica para a produção de matéria seca foi alcançada com a aplicação de 41,6 mg dm</span><span class="A9"><sup><span>-3</span></sup></span><span>de P, associada com adição 500 mg dm</span><span class="A9"><sup><span>-3 </span></sup></span><span>de calcário dolomítico.</span></p><p class="Default"> </p>

Pretreatment with low-dose gamma irradiation enhances tolerance to the stress of cadmium and lead in Arabidopsis thaliana seedlings

Heavy metals are important environmental pollutants with negative impact on plant growth and development. To investigate the physiological and molecular mechanisms of heavy metal stress mitigated by low-dose gamma irradiation, the dry seeds of Arabidopsis thaliana were exposed to a Cobalt-60 gamma source at doses ranging from 25 to 150Gy before being subjected to 75µM CdCl2 or 500µM Pb(NO3)2. Then, the growth parameters, and physiological and molecular changes were determined in response to gamma irradiation. Our results showed that 50-Gy gamma irradiation gave maximal beneficial effects on the germination index and root length in response to cadmium/lead stress in Arabidopsis seedlings. The hydrogen peroxide and malondialdehyde contents in seedlings irradiated with 50-Gy gamma rays under stress were significantly lower than those of controls. The antioxidant enzyme activities and proline levels in the irradiated seedlings were significantly increased compared with the controls. Furthermore, a transcriptional expression analysis of selected genes revealed that some components of heavy metal detoxification were stimulated by low-dose gamma irradiation under cadmium/lead stress. Our results suggest that low-dose gamma irradiation alleviates heavy metal stress, probably by modulating the physiological responses and gene expression levels related to heavy metal resistance in Arabidopsis seedlings.

不同种源油松幼苗的光合色素和非结构性碳水化合物对模拟氮沉降的短期响应

PDF HTML阅读 XML下载 导出引用 引用提醒 不同种源油松幼苗的光合色素和非结构性碳水化合物对模拟氮沉降的短期响应 DOI: 10.5846/stxb201312122936 作者: 作者单位: 北京林业大学森林资源与生态系统过程北京市重点实验室,北京林业大学森林资源与生态系统过程北京市重点实验室,北京林业大学森林资源与生态系统过程北京市重点实验室,北京林业大学森林资源与生态系统过程北京市重点实验室,北京林业大学森林资源与生态系统过程北京市重点实验室,北京林业大学森林资源与生态系统过程北京市重点实验室 作者简介: 通讯作者: 中图分类号: 基金项目: 中央高校基本科研业务费专项资金资助(TD2011-07);国家自然科学基金青年基金(31000263) Short term responses of photosynthetic pigments and nonstructural carbohydrates to simulated nitrogen deposition in three provenances of Pinus tabulaeformis Carr. seedlings Author: Affiliation: The Key Laboratory for Forest Resources Ecosystem Processes of Beijing,Beijing Forestry University,The Key Laboratory for Forest Resources Ecosystem Processes of Beijing,Beijing Forestry University,The Key Laboratory for Forest Resources Ecosystem Processes of Beijing,Beijing Forestry University,The Key Laboratory for Forest Resources Ecosystem Processes of Beijing,Beijing Forestry University,The Key Laboratory for Forest Resources Ecosystem Processes of Beijing,Beijing Forestry University,The Key Laboratory for Forest Resources Ecosystem Processes of Beijing,Beijing Forestry University Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:以不同种源(内蒙NM、北京BJ和山西SX)的3年生油松幼苗为研究对象,研究不同种源油松幼苗的光合色素以及非结构性碳水化合物(NSC)对氮沉降增加的短期响应。实验中设置5个氮处理:CK(0 kg hm-2 a-1)、N1(15 kg hm-2 a-1)、N2(25 kg hm-2 a-1)、N3(50 kg hm-2 a-1)、N4(150 kg hm-2 a-1)。研究结果表明:(1)不同生长季,3个种源油松幼苗的光合色素对氮沉降增加的响应存在差异,但是只有BJ种源油松幼苗的叶绿素含量在生长季中期受到了氮沉降增加的显著促进作用,并在N4水平下达到最大值。(2)氮沉降的增加促进了3个种源油松幼苗NSC的转移和消耗,在生长季初期和中期,随着氮沉降水平的升高,3个种源油松幼苗的可溶性糖(SS)含量、淀粉(ST)含量以及总非结构性碳水化物(TNC)含量呈不同程度的降低。生长季末期,3个种源油松幼苗的SS和TNC明显积累。N4水平抑制了NM种源油松幼苗SS和BJ种源油松幼苗ST的累积,促进了NM种源油松幼苗ST含量和BJ种源油松幼苗SS含量的提高。氮沉降的增加显著抑制了SX种源油松幼苗NSC的积累,延长了幼苗的生长期,推迟了幼苗进入休眠的时间。 Abstract:Nitrogen (N) deposition has noticeably increased in China in recent years, which is expected to have influenced the physiological characteristics of Pinus tabulaeformis Carr. To improve our understanding about the effects of elevating N deposition on P. tabulaeformis, the short-term responses of the photosynthetic pigments and nonstructural carbohydrates (NSC) in seedlings with three provenances were studied. We set up a simulated N experiment with three provenances of 3-year-old P. tabulaeformis seedlings on Lingkong Mountain in Shanxi Province. The three provenances were Neimeng (NM), Beijing (BJ), and Shanxi (SX). Five N treatments with three replications were designed, including CK (0 kg hm-2 a-1), N1 (15 kg hm-2 a-1), N2 (25 kg hm-2 a-1), N3(50 kg hm-2 a-1) and N4 (150 kg hm-2 a-1). The source of N was NH4NO3 and fertilization was carried out five times in 2012. The contents of the photosynthetic pigment and nonstructural carbohydrate in the seedlings with three provenances were measured under different N treatments in June, August, and October, 2012. The results showed that: in different growing seasons, photosynthetic pigments exhibited various responses to elevated N deposition in P. tabulaeformis seedlings, regardless of provenance. In the early growing season, the photosynthetic pigment contents showed no significant response to the addition of N in any of the seedlings. In the intermediate growing season, the chlorophyll content of BJ provenance seedlings increased significantly under elevated N deposition treatments, reaching a maximum under the N4 treatment. There was no significant increase in the chlorophyll content of provenances NM and BJ increased after adding N. In the late growing season, the photosynthetic pigment content of provenance SX was lowest under the N1 treatment and increased under the N2, N3, and N4 treatments, with no significant differences to CK. The photosynthetic pigment contents of NM and BJ provenances seedlings were not affected by N deposition. Elevated N deposition promoted the transfer and consumption of nonstructural carbohydrate (NSC) in all three seedlings. In the early growing season, N addition significantly reduced soluble sugar (SS) and total nonstructural carbohydrate (TNC) content in the NM provenance seedlings, the TNC content in BJ provenance seedlings, and the SS content in SX provenance seedlings. In the intermediate growing season, the SS, starch (ST), and TNC contents in NM provenance seedlings were lowest under the N4 treatment. In contrast, in SX provenance seedlings, these three indexes reached minimum values under the N3, N1, and N2 treatments, respectively. The SS, ST, and TNC in BJ provenance seedlings showed no significant responses to N deposition. In the late growing season, SS and TNC content noticeably increased in the seedling needles of all three provenances; however, they exhibited various responses to different N deposition levels. The TNC contents in the seedlings of NM and BJ provenances were not significantly influenced by elevated N deposition. High N deposition (N4 treatment) inhibited SS accumulation in NM provenance seedlings, but increased SS content in BJ provenance seedlings. In addition, high N deposition clearly inhibited ST in BJ provenance seedlings, but increased ST content in NM provenance seedlings. Elevated N deposition significantly inhibited NSC accumulation in SX provenance seedlings, which delayed seedling dormancy and extended the growing period of seedlings. 参考文献 相似文献 引证文献

Effect of Kinetin on Physiological and Biochemical Properties of Maize Seedlings under Arsenic Stress

The effects of different levels of kinetin (KT) application on the growth, biomass, contents of chlorophyll (Chl a, Chl b, and carotenoid), arsenic uptake, and activities of antioxidant enzymes in maize seedlings under arsenic (As) stress were investigated by a hydroponic experiment. The results showed that KT supplementation increased the biomass in terms of root length, root number, fresh weight, and seedling length, and KT treatments also improved the contents of Chl a, As uptake, and Chl a : b ratio compared to cases with As treatment alone. However, no significant changes were observed in carotenoid content, and a reduction was found in Chl b content of seedlings. KT also increased the activities of catalase (CAT), peroxidase (POD), and superoxide dismutase (SOD) in the leaves of maize seedlings when 0.1 mg/L KT and As were applied, which decreased the content of malondialdehyde (MDA). These results suggested that KT could alleviate the toxicity of As to maize seedlings by keeping the stability of chlorophyll, enhancing the activities of antioxidant enzymes, and inhibiting the lipid peroxidation. In conclusion, the alleviation effect of KT in maize seedlings exposed to As stress was clearly observed in the present study.

QTLs for Shoot Length and Chlorophyll Content of Rice Seedlings Grown under Low-Temperature Conditions, using a Cross between Indica and Japonica Cultivars

Quantitative trait loci (QTLs) affecting the shoot length and chlorophyll content of seedlings grown at a low temperature (16ºC) for 4 weeks were analyzed using inbred lines derived from a cross between an indica rice cultivar, Habataki, and a japonica rice cultivar, Arroz da Terra. Culm length of the inbred lines, measured at the harvesting stage, was also analyzed. The QTLs linked to increased shoot length (qSL1 ) and culm length (qCL1 ) on the Arroz da Terra allele were detected in the same region of chromosome 1, where the gibberellin 20 oxidase-2 gene (identical to Semi Dwarf1 : SD1 ) located. Other QTLs ( qSL and qSL8 ) that were linked to increased shoot length on Arroz da Terra and Habataki alleles, but had no effects on the culm length, were detected on chromosomes 3 and 8, respectively. The alleles of qSL3 and qSL8 might improve early shoot growth without increasing the risk of lodging caused by a long culm length. A novel QTL (qCC1 ) linked to increased chlorophyll content of seedlings grown at low temperatures through the effect of an Arroz da Terra allele was detected on chromosome 1, but it differed in position from the QTLs for shoot length.

Comparative Effect of Nitrogen Forms on Nitrogen Uptake and Cotton Growth Under Salinity Stress

The effects of nitrogen (N) forms (ammonium- or nitrate-N) on plant growth under salinity stress [150 mmol sodium chloride (NaCl)] were studied in hydroponically cultured cotton. Net fluxes of sodium (Na+), ammonium (NH4+), and nitrate (NO3−) were also determined using the Non-Invasive Micro-Test Technology. Plant growth was impaired under salinity stress, but nitrate-fed plants were less sensitive to salinity than ammonium-fed plants due mainly to superior root growth by the nitrate-fed plants. The root length, root surface area, root volume, and root viability of seedlings treated with NO3-N were greater than those treated with NH4-N with or without salinity stress. Under salinity stress, the Na+ content of seedlings treated with NO3-N was lower than that in seedlings treated with NH4-N owing to higher root Na+ efflux. A lower net NO3− efflux was observed in roots of nitrate-fed plants relative to the net NH4+ efflux from roots of ammonium-fed plants. This resulted in much more nitrogen accumulation in different tissues, especially in leaves, thereby enhancing photosynthesis in nitrate-fed plants under salinity stress. Nitrate-N is superior to ammonium-N based on nitrogen uptake and cotton growth under salinity stress.

Effects of Zeolite on Seedling Quality and Nutrient Contents of Cucumber Plant (Cucumis sativus L. cv. Mostar F1) Grown in Different Mixtures of Growing Media

Zeolite has been successfully used in growing media for containerized production systems. In this study the effects of zeolite utilization with the mixture of different growing media (GM) on the seedling quality and nutrient contents of cucumber (Cucumis sativus L. cv. Mostar F1) were determined under the greenhouse conditions. For this purpose, natural zeolite, perlite, turf, and their different mixture forms were used as GM for growing of cucumber seedlings. Effects of these substances on the seed germination, plant height, stem diameter, seedling fresh weight, and macronutrient [nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg)] and micronutrient [iron (Fe), zinc (Zn), manganese (Mn), and copper (Cu)] contents were studied. As a result of this study, the effects of GM on the seedling quality parameters were found to be significant for seed germination, plant height, stem diameter and fresh weight, and nutrient contents of seedlings. The best results were generally obtained from turf + zeolite mixtures.

Stomatal Opening, Transpiration, and Need/e Moisture in Loblolly Pine Seedlings From Two Texas Seed Sources

Relationships among percentage of open stomates, transpiration, and needle moisture content in seedlings of loblolly pine of two Texas provenances were studied under changing soil moisture conditions. Needle moisture content correlated very well with transpiration under favorable moisture conditions, and with percentage of open stomates under soil moisture stress. Transpiration and percentage of open stomates were correlated under a wide range of moisture conditions. Foliage moisture content was still relatively high in both ecotypes when stomates closed and transpiration drastically declined. The Lost Pines seed source appeared to have superior ability to conserve moisture under droughty conditions by closure of stomares and reduction of transpiration. FOREST SCI. 23: 457-462.

Differential activity and expression of antioxidant enzymes and alteration in osmolyte accumulation under high temperature stress in wheat seedlings

The objective of this study was to investigate the effects of high temperature (HT) stress on activity and expression of antioxidant enzymes and osmotic adjustment substance content in seedlings of four wheat cultivars with contrasting levels of HT tolerance. The results showed that the differences in superoxide dismutase (SOD) activity, glutathione reductase (GR) activity, soluble protein content and proline content between HT-resistant cultivars and HT-sensitive cultivars were more obvious than those in the activities of peroxidase (POD) and catalase (CAT). Moreover, the transcript levels of Fe-SOD and Mn-SOD were consistent with the trend of variation in SOD activity, which suggested that Fe-SOD and Mn-SOD might play important roles in SOD activity under HT stress. Finally, the transcript levels of CAT and GR were more sensitive than the activities of CAT and GR in response to HT stress in wheat seedlings. Collectively, our results indicated that HT-resistant wheat cultivars had higher SOD activity, GR activity and proline content than HT-sensitive wheat cultivars under HT stress. These data indicated that HT-resistant wheat cultivars resisted the damage caused by HT stress more effectively, which could be applied in predicting HT-resistant wheat cultivars used for field production.

Effects of biochar on photosynthesis and antioxidative system of Malus hupehensis Rehd. seedlings under replant conditions

The purpose of this study was to investigate the mechanisms and effects of biochar on the plant growth of Malus hupehensis Rehd. seedlings under replant conditions. Before the M. hupehensis Rehd. seedlings were planted in pots, biochar was added to pots filled with replant soil at four rates: 0, 5, 20, 80gkg−1. The growth of seedlings was monitored with plant height and photosynthesis. The antioxidant enzyme activities, lipid peroxidation and osmotic regulation substance contents in seedlings leaves were also measured. The phenolic compounds in the four soil treatments were detected too. The results showed that the addition of biochar significantly decreased the contents of phenolic acids in replant soil through the sorption of biochar. In comparison with the control, biochar applied to replant soil at 80gkg−1 enhanced the plant height, fresh weight, and photosynthetic parameters. Furthermore, seedlings in soil treated with biochar, particularly at 80gkg−1, exhibited higher activity of antioxidant enzymes including superoxide dismutase, peroxidase, catalase, and ascorbate peroxidase. With the addition of biochar, the contents of malondialdehyde, O2•− and H2O2 significantly decreased, and the osmotic substances accumulation in leaves also declined. These results suggested that the addition of biochar can alleviate apple replant disease by activating antioxidant enzymes, decreasing lipid peroxidation, and significantly reducing the phenolic acids content of replant soil through the sorption of biochar.

Seed Treatment with Salicylic Acid Enhance Drought Tolerance in Capsicum

Salicylic acid is a natural chemical used to enhance biotic and abiotic stress tolerance in plants. In our experiment we studied about the effect of salicylic acid on the growth of the capsicum under water stress condition. Four concentrations (0.25, 0.50, 1.00 and 2.00 mM) of salicylic acid (SA) were applied through seed soaked method. Pretreatment with salicylic acid improved the majority of physiological and morphological parameters measured in capsicum seedling and plants. Results showed that SA treatment reduced the injury rating value, electrolyte leakage and increased proline content in seedlings, the dry matter of plants and ultimately yield. The best drought protection observed when the seeds were soaked in 0.50 mM SA.

Glycerol Affects Root Development through Regulation of Multiple Pathways in Arabidopsis

Glycerol metabolism has been well studied biochemically. However, the means by which glycerol functions in plant development is not well understood. This study aimed to investigate the mechanism underlying the effects of glycerol on root development in Arabidopsis thaliana. Exogenous glycerol inhibited primary root growth and altered lateral root development in wild-type plants. These phenotypes appeared concurrently with increased endogenous glycerol-3-phosphate (G3P) and H2O2 contents in seedlings, and decreased phosphate levels in roots. Upon glycerol treatment, G3P level and root development did not change in glycerol kinase mutant gli1, but G3P level increased in gpdhc1 and fad-gpdh mutants, which resulted in more severely impaired root development. Overexpression of the FAD-GPDH gene attenuated the alterations in G3P, phosphate and H2O2 levels, leading to increased tolerance to exogenous glycerol, which suggested that FAD-GPDH plays an important role in modulating this response. Free indole-3-acetic acid (IAA) content increased by 46%, and DR5pro::GUS staining increased in the stele cells of the root meristem under glycerol treatment, suggesting that glycerol likely alters normal auxin distribution. Decreases in PIN1 and PIN7 expression, β-glucuronidase (GUS) staining in plants expressing PIN7pro::GUS and green fluorescent protein (GFP) fluorescence in plants expressing PIN7pro::PIN7-GFP were observed, indicating that polar auxin transport in the root was downregulated under glycerol treatment. Analyses with auxin-related mutants showed that TIR1 and ARF7 were involved in regulating root growth under glycerol treatment. Glycerol-treated plants showed significant reductions in root meristem size and cell number as revealed by CYCB1;1pro::GUS staining. Furthermore, the expression of CDKA and CYCB1 decreased significantly in treated plants compared with control plants, implying possible alterations in cell cycle progression. Our data demonstrated that glycerol treatment altered endogenous levels of G3P, phosphate and ROS, affected auxin distribution and cell division in the root meristem, and eventually resulted in modifications of root development.

Plant growth-promoting rhizobacteria improved growth, nutrient, and hormone content of cabbage (Brassica oleracea) seedlings

A greenhouse experiment was conducted to observe the effects of Bacillus megaterium strain TV-91C, Pantoea agglomerans strain RK-92, and B. subtilis strain TV-17C inoculation on the growth, nutrient, and hormone content of cabbage seedlings. The seeds of cabbage were incubated in flasks by shaking at 80 rpm for 2 h at 28 °C to coat the seeds with the rhizobacteria. Plant growth-promoting rhizobacteria (PGPR) treatments increased fresh and dry shoot and root weight, stem diameter, seedling height, chlorophyll reading values, and leaf area of cabbage seedlings compared with the control. Among the strains, B. megaterium TV-91C gave the greatest seedling nutrient content and growth parameters, although the maximum values for leaf area, gibberellic acid, salicylic acid, and indole acetic acid (IAA) contents of seedlings were obtained with the P. agglomerans RK-92 treatment. Seed inoculation with B. megaterium TV-91C increased fresh and dry shoot and root weight by 32.9%, 22.6%, 16.0%, and 35.69%, respectively. Inoculations also increased the stem diameter, seedling height, and SPAD chlorophyll values by 47.5%, 27.2%, and 5.8%, respectively. Furthermore, compared to the control, P. agglomerans RK-92 increased gibberellic acid, salicylic acid, IAA, and leaf area by 13.9%, 70.9%, 38.5%, and 27.3%, respectively. PGPR treatments may improve seedling growth and quality in cabbages.

Specific effects of certain salts on nitrogen metabolism of young corn seedlings

The effect of sodium and magnesium chlorides and sulphates on nitrogen metabolism of corn seedlings and their constituent parts have been studied. Treatment with all salts led to a decrease in the nitrogen content of the seedling as a whole, and the decrease became more pronounced with the increase of salt concentration, though these concentrations were too low to induce any osmotic action. The same trend of changes was noticed as regards nonprotein-N, whereas the opposite was recorded in reference to the changes; of protein-N. Higher concentrations of the salt solutions led to leaching out of more nonprotein-N than did lower concentrations. The study of the distribution of nitrogenous constituents among the different organs of the seedling showed that while the total-N content of the whole seedling decreased with the increase of salt concentration, the total-N content of the roots decreased markedly, and the total-N content of the tops decreased also but less whereas, the total-N content of the grains increased with the increase of salt concentration as compared with that in the control. As a result of disturbances of nitrogen metabolism under salinization, more ammonia and amides were accumulated in all seedling organs.

Effect of an IAA overproducer mutant of the fungus hebeloma Cylindrosporum romagnesi on the early stages of ectomycorrhizal infection and carbohydrate content in seedlings of Pinus pinaster (ait.) SOL.

Ectomycorrhizal and control seedlings of <i>Pinus pinaster</i> were cultured on a synthetic Melin-Norkrans medium in Petri dishes. Seedlings were inoculated with a mycelial slurry of an indole-3-acetic acid (IAA) overproducer <i>Hebeloma cylindrosporum</i> mutant 331. The wild strain <i>H. cylindrosporum</i> hl was used as a reference. Medium was supplemented or not with glucose. The mycelial slurry appeared to be very effective for mycorrhizal inoculation even on the medium without glucose. In such culture conditions ectomycorrhizal ability of the IAA overproducer mutant 331 was significantly higher than of the comparable wild type. The highest content of soluble sugars was found in stems and roots of plants mycorrhizal with the mutant followed by mycorrhizal plants with the wild type and then by the uninoculated control. Sucrose practically disappeared from roots of mycorrhizal plants. Starch content in roots of mycorrhizal plants with the IAA overproducer mutant was lower as compared with other treatments. Fungal auxin in mycorrhizal symbiosis seems to be responsible for maintaining the source-sink relationship. This is revealed by higher sugar level in the host's photosynthetic tissue (source) and the rise of soluble sugar content in roots (sink) due to enhanced translocation of sugars to the roots and auxin stimulated conversion of carbohydrates (sucrose, starch) of the host.

Specific effects of certain salts on carbohydrate metabolism in young corn seedlings

The effects of sodium and magnesium chlorides and sulphates on carbohydrate metabolism of corn seedlings and their component parts were studied. There was a decrease in the total carbohydrate content of seedlings with advance of time, in control and in different concentrations of salts. The decrease became less marked with increase of salt concentrations. The main effect of salinization, on the changes in carbohydrates, was strongest on the roots and grains. The roots contained the lowest proportion of the various carbohydrate fractions. This feature suggests that the mobilization of carbohydrates from grains to roots is greatly retarded by salinization. Both cations and anions exert an influence on the conversion of reserve carbohydrates.

Seed photosynthesis enhances Posidonia oceanica seedling growth

Posidonia oceanica seeds demonstrate photosynthetic activity during germination as well as throughout seedling development, a fact which suggests that seed photosynthesis can influence seedling growth. This study examines the contribution of seed photosynthesis to changes in leaf and root biomass, the concentration of seed carbohydrate reserves (free sugars and starch) and elemental C, N and P content in seedlings exposed to different light/dark treatments. Green seeds attached to seedlings remained photosynthetically active for three months and photosynthetic activity in the seeds enhanced seedling growth in leaves and roots. It was estimated that ca. 29.26% of leaf biomass and ca. 42.31% of root biomass production was due to seed photosynthetic activity. Photosynthesis occurred at a higher rate in seeds than in leaves during early seedling growth, and extreme light limitation reduced the mobilization of carbon reserves stored in the seeds. These adaptations control leaf self‐shading and plant competition in well‐established P. oceanica beds while also promoting increased seedling survival rates in open, uncolonised areas where clonal growth is limited.