Root Browning in Pinus banksiana Lamb. and Eucalyptus pilularis Sm. 1. Anatomy and Permeability of the White and Tannin Zones

Growing tree roots are characteristically brown with white tips. The browning process, which occurs as the white region matures, has often been attributed to the deposition of suberin in various tissues. However, in pouch-grown tree seedlings of jack pine (Pinus banksiana Lamb.) and eucalyptus (Eucalyptus pilularis Sm.), browning was not linked to suberization but was caused by the deposition of condensed tannins in the walls of all cells external to the stele. Therefore, we propose using the term “tannin zone” to refer to this region of the root. Vitality tests indicated that the cells of the epidermis and cortex were alive in white regions but were dead in brown regions. Following sequential treatment with berberine hemisulfate and potassium thiocyanate, the cortical walls external to the endodermal Casparian band were full of berberine thiocyanate crystals, indicating that they were permeable to berberine. These walls should also be permeable to water and ions, which have smaller molecular dimensions than the tracer dye. Based on the anatomy and permeability of the tannin zone, we predict that its capacity for ion uptake would be reduced compared to the white zone because of a reduced absorptive plasmalemma surface area. In jack pine, some uptake could be effected by the passage cells of the endodermis. The tannin zone should be even less absorptive in eucalyptus because the exodermis remains an apoplastic barrier and the endodermis lacks passage cells. It is difficult to predict the difference between the tannin and white zones with respect to water uptake. Death of the cells external to the endodermis would reduce the resistance of the root to water movement, but deposition of tannins would increase it. The deposition of suberin lamellae in increasing numbers of endodermal cells may also retard water flow. The anatomy and physiological properties of the tannin zone are unique from those of the distal, white zone and the proximal, cork-clad zone.     

The Effect of Lateral Root Outgrowth on the Structure and Permeability of the Onion Root Exodermis

Lateral root development in onion is accompanied by a variety of anatomical and permeability changes in some cells of the adventitious root. The endodermal Casparian band of the parent root is disrupted early in the development of the lateral but later extends so as to be continuous with the developing Casparian band of the new root. The lateral root emerges through a longitudinal split in the adventitious root exodermis and epidermis. Following this, the cell walls and intercellular air spaces adjacent to the lateral become incrusted with suberin and a small amount of lignin, forming a collar of modified tissue around the lateral. Subsequent radial expansion of the lateral distorts the adjacent cells of the adventitious root and forces a tight association between it and the lateral. The apoplastic permeability of lateral/parent root junctions was tested using Cellufluor, an apoplastic fluorescent dye which binds to cellulose. Prior to lateral root emergence, no dye enters the parent root cortex due to the Casparian band of the exodermis. Immediately after emergence, dye often penetrates through the break in the exodermal Casparian band and diffuses into the first cortical cell layer. However, when the collar of suberized cells develops (two days after lateral root emergence), movement of the dye into an undisturbed adventitious root is usually prevented (i.e., in 77% of the cases examined). In contrast, only 17% of the root systems which were transplanted just prior to treatment excluded the dye. This indicates that the apoplastic seals around the laterals are sensitive to movement and we recommend that only undisturbed root systems be used for permeability studies.     

Root and shoot elongation of rhizotron-grown seedlings of Eucalyptus nitens and Eucalyptus globulus in relation to temperature

Information on the growth response of a crop plant in relation to temperature can be helpful in selecting genotypes to suit local environments, scheduling favourable time of planting and forecasting growth and yield. To determine the effects of varying temperature on root and shoot elongation of eucalypt seedlings, elongation rates of roots and shoots were measured in rhizotrons for two species (Eucalyptus nitens (Deane and Maiden) Maiden, and Eucalyptus globulus Labill.) at a temperature range of 5–23 °C. Within this range of temperatures, elongation rates of roots and shoots of both species increased with an increase in temperature. Roots of E. globulus were more sensitive and shoots less sensitive to temperature than those of E. nitens. However, the threshold temperature corresponding with zero elongation rate predicted from the regression of elongation rate against temperature was similar for the roots (∼5 °C) and shoots (∼0 °C) of both species. Hysteresis did not appear to have a significant influence on root or shoot elongation of both species during warming compared with cooling. Results are discussed highlighting the importance of the interaction between development and growth of plant components.     

Removal of the stem terminal and application of auxin change carbohydrates in Pinus banksiana cuttings during propagation

This study determined how surgical removal of the stem terminal, with indole-3-butyric acid (IBA) treatment, influenced concentrations and partitioning of carbohydrates in Pinus banksiana Lamb, cuttings during propagation. Seedlings and cuttings that originated from 90-day-old stock plants were untreated or treated by removing the stem terminal, followed by application of IBA to the severed apical or basal (cuttings only) stem. Fresh and dry weights of the basal 1-cm stems of cuttings were determined daily for the first 10 days of propagation (i.e., before roots were visible). In addition, basal 1-cm stems, upper (ca 9-cm) stems and needles of seedlings and cuttings were analyzed for sucrose, soluble reducing sugar and total non-structural carbohydrate. Net concentrations of each carbohydrate in cuttings were obtained by subtracting corresponding concentrations for similarly treated seedlings, yielding data directly related to only the physiology of rooting. Data for cuttings indicated that presence of the stem terminal combined with applied IBA positively influenced rooting through processes that increased basal stem fresh and dry weights before root emergence. Removal of the stem terminal influenced accumulation of net total carbohydrate in cuttings, but the major effect was on carbohydrate partitioning. Either type of IBA treatment after removal of the stem terminal usually resulted in different net carbohydrate concentrations in each tissue source of cuttings, compared with only removal of the terminal. Neither basal nor apical IBA treatment of cuttings without stem terminals yielded results for carbohydrate accumulation and partitioning like those obtained with intact cuttings. Removal of the stem terminal, even if followed by IBA treatment, may have lessened rooting potential of cuttings because it resulted in greater reducing sugarstarch concentration ratios in basal stems compared with those in intact cuttings.     

Root Anatomy and Mycotrophy of the Achlorophyllous Voyria tenella Hook. (Gentianaceae)

The central cylinder of the root of Voynet tenella consists of up to ten central, non-lignified, tracheidal xylem elements surrounded by some parenchymatic tissue and 5–7 groups of phloem. A pericycle could not be discerned. Even though the endodermis carries a faint suberin lamella it cannot be discerned anatomically without special staining. The cells of the 1–3 cortex layers next to the endodermis are elongated longitudinally, the subsequent cortex parenchyma is multi-layered and consists of isodiametric cells. The cells of the 2–3 layered outer dermal tissue are smaller than those of the adjacent cortex, their walls carry a suberin lamella and the outermost of them constantly scale off. The dermal tissue is interpreted as a multilayered exodermis. The fungal colonization in roots of Voyria tenella remarkably differs from any known mycorrhizal pattern. After having penetrated the dermal tissue, the always intracellularly-growing hyphae head straight towards the inner cortex layers, where they spread along the central cylinder. Ramifications from these inner-spreading hyphae then colonize the cortex parenchyma from the inside and they develop dense hyphal coils. Eventually, the coiled hyphae swell and collapse, resulting in amorphous clumps of fungal material. This mycorrhizal pattern is referred to as an intraradical fungus garden. Arguments are given to call the mycorrhiza in Voyria tenella a specialized arbuscular mycorrhiza. Phylogenetic and ecological implications of the observations and the results are discussed.     

四种冷冻保护剂对小鼠2-细胞胚胎渗透性和毒性作用的比较

作为胚胎冷冻保存的基础性研究,冷冻保护剂的渗透性和毒性研究非常重要.本试验选用1,2-丙二醇、甘油、乙二醇和二甲基亚砜4种常用冷冻保护剂,对小鼠2-细胞胚胎进行渗透性和毒性研究.结果显示:1.5 mol/L的1,2-丙二醇、乙二醇和二甲基亚砜冷冻保护剂对2-细胞胚胎的渗透性显著高于甘油保护剂;4种冷冻保护剂对细胞膜的完整性没有影响;1.5 mol/L的乙二醇、1,2-丙二醇和甘油保护剂处理后的2-细胞胚胎的囊胚发育率和孵化率与对照组胚胎比较差异不显著(P>0.05),但显著高于二甲基亚砜处理后的2-细胞囊胚发育率和孵化率(P<0.01).结果表明:在4种冷冻保护剂中,乙二醇和1,2-丙二醇适合于小鼠2-细胞胚胎冷冻保存     

Impact of clear-cutting and prescribed burning on microbial diversity and community structure in a Jack pine (Pinus banksiana Lamb.) clear-cut using Biolog Gram-negative microplates

Three isolates ofFusarium avenaceum are pathogenic on spotted knapweed(Centaurea maculosa), a major weed plant of pasturelands and rangelands of the Pacific Northwestern USA. One isolate (no. 1) obtained from the European centre of origin of knapweed and isolate no. 365 native to Montana, did not significantly affect knapweed seed germination. However,F. avenaceum no. 1003, another Montana native isolate, caused a 100% decrease in seed germination and hence, no seedling emergence. When formulated, isolate no. 1003, could be recovered from treated soils after 7 days and caused a significant reduction in seedling emergence or seedling dry weight. This organism had no effect on the germination ofTriticum aestivum orMedicago sativa, but did affect the germination of other plant species.F. avenaceum appears to be a candidate for the biocontrol of spotted knapweed, however, a native isolate is potentially more effective than an isolate obtained from the centre of origin ofC. maculosa.     

Root anatomy of <Emphasis Type=Italic>Pinus taeda</Emphasis> L.: seasonal and environmental effects on development in seedlings

The environmental and seasonal effects on anatomical traits of Pinus taeda L. seedling roots were studied in the laboratory in three contrasting root growth media and also in typical outdoor nursery culture. Growth media with lower water regimen and high penetration resistance caused a reduction in lengths of the white and condensed tannin (CT) zones and acceleration of development of suberin lamellae in the endodermis. As a possible counter to this reduction in zone lengths, second-order laterals were produced closer to the tips of first-order laterals. This suggested there may be an advantage to producing more shorter roots under stressful conditions. Under outdoor nursery conditions (June to mid-December) the white zone was always a rather small part of the root system surface area (4.5% in December), but it dominated as a provider of cortical plasmalemma surface area (CPSA) in contact with modified soil solution (65% in December) because of its live cortex and capacity to increase nearly three fold the amount of CPSA per unit root length. The CT zone always provided most of the total root surface area (80% in December). Although it had no live cortex, a few cells of the CT zone endodermis remained non-suberized passage cells, perhaps giving this major part of the root system some capacity for ion and water absorption. A late summer increase in CPSA was due largely to the rapid production of mycorrhizae. Root systems were capable of very rapid replacement of roots lost due to undercutting and lateral root pruning. The great variation in CPSA per unit root length contained in the white, mycorrhizal and CT zones suggested a capacity to adapt rapidly to changing conditions.     

Microtubule pattern and the occurrence of pre-prophase bands in embryogenic cultures of black spruce (Pieca mariana Mill.) and non-embryogenic cultures of jack pine (Pinus banksiana Lamb.)

Summary The organization of microtubules during interphase and prophase in embryogenic cultures of black spruce (Picea mariana) was investigated by indirect immunofluorescence. Somatic embryos of black spruce possessed an extensively branched and interconnecting network of fine interphase cortical microtubules. The development of pre-prophase bands (PPBs) in embryogenic black spruce cultures was compared with that in non-embryogenic cell cultures of jack pine (Pinus banksiana). PPBs in both species were initially arranged as a very broad array of microtubules, later (early to mid-prophase) becoming narrower and more intensely fluorescent. The occurrence of pre-prophase bands in relation to the number of phragmoplasts (i.e. PPB index) of black spruce somatic embryos was significantly higher (p<0.01) than that found for jack pine cells.     

Permeability studies in chitosan membranes. Effects of crosslinking and poly(ethylene oxide) addition

Pure chitosan, glutaraldehyde crosslinked chitosan, and a blend of chitosan with poly(ethylene oxide) (PEO) membranes were prepared. The three membranes were characterized in terms of their swelling capacities as well as their permeabilities to a drug model (sulfamerazine sodium salt). For the permeation experiments, the variables analyzed were the type of membrane and the initial drug concentration in the liquid phase (from 0.1% to 1.5%). Permeability coefficients were calculated using UV spectroscopy. The results showed that for the three analyzed membranes, the permeability did not change with time (over the studied time interval). An increase in the permeability for CHI/PEO membranes compared to those made of pure chitosan was also observed, possibly due to microporous region formation and/or crystallinity reduction. For the crosslinked membrane, an even higher increase in the permeability coefficient was observed. In this case, the increase was attributed to free volume variation.     

Effects of aluminium on growth and cation uptake in seedlings of Eucalyptus mannifera and Pinus radiata

This experiment was designed to examine the effects of aluminium (Al) on the growth of Pinus radiata (D. Don) and Eucalyptus mannifera subsp. mannifera (Mudie) seedlings in culture solutions in a glasshouse to help explain the failure of radiata pine trees on some acid, low fertility soils in Australia on which the native eucalypts flourish. Aluminium (Al) in culture solution increased the growth of roots and shoots of seedlings of both species but while growth of the eucalypt continued to increase with increases in Al to 2.222 μM, growth of the pine was largest at 370 μM Al. In addition to total root length, specific root length (length per unit dry weight), a measure of fineness of the root, increased in the eucalypt seedlings as the substrate Al increased. Growth of the shoots and roots of the pine in the absence of any added Al was extremely poor suggesting that Al, in low concentrations, may be an essential element or ameliorate some other factors in solution culture at low pH. Root and shoot concentrations of K increased with increasing Al, whilst Ca and Mg Concentrations decreased and Mn concentrations were unaffected in both species. Tissue Ca and Mg concentrations were 2 to 3 times higher in the eucalypt seedlings than the pine at all levels of added Al due to greater uptake of these elements by the eucalypt. In contrast, at the highest concentration of Al in the medium, shoot Al concentrations were lower in the cucalypt than in the pine due to a greater proportion of Al being retained in the eucalypt roots. These differences between the seedlings in terms of root growth and tissue cation concentrations may help explain the ability of eucalypt species to maintain vigorous growth on acid soils high in Al and low in Ca and P, where growth of the pines failed.     

CO_2 倍增对长白赤松幼苗根 土界面水分运输过程的影响(英文)

用具有非破坏性的电导率方法测定土壤水分的廓线 ,与挖掘法 (或打孔法 )获取的根系分布对比 ,研究CO2倍增条件下一年生的长白赤松 (PinussylvestrisLinn .var.sylvestriformis (Takenouchi)ChengetC .D .Chu)幼苗根 土界面的水分运输状态。结果表明 :(1)土壤水分廓线由植物的活性所调制 ,根系分布密集的土层其水分含量也高。(2 )CO2 倍增 ,根系 土壤水分运输的活跃层及根系分布都将向土壤深处位移。研究证明 ,电导率方法能够指示发生于根 土界面上的水分运输状态 ,方法简单 ,且对土壤无破坏     

外源硫化氢对豌豆根尖及其边缘细胞的影响

为研究外源硫化氢（H2S）对豌豆（Pisum sativum）胚根生理特性及其边缘细胞的影响,测定了不同浓度外源H2S处理下豌豆根长、根尖组织可溶性蛋白质含量、抗氧化酶（APX、CAT、POD和SOD）活性、根尖边缘细胞存活率及其粘胶层相对面积的变化。结果表明：低浓度（0-40μmol·L-1）H2S可促进豌豆胚根生长,根尖组织可溶性蛋白质含量升高,SOD、APX和POD活性增加,CAT活性降低,根尖边缘细胞存活率上升,粘胶层相对面积变小。高浓度（60-80μmol·L-1）H2S可抑制豌豆胚根生长,可溶性蛋白质含量和边缘细胞存活率明显下降,APX和POD活性降低,CAT活性升高,SOD活性没有明显变化,粘胶层相对面积变大;边缘细胞染色体凝集并边缘化,然后逐渐降解并伴随粉末化,细胞质膜皱缩。因此,推测H2S可能在植物体内发挥着重要的生理作用。     

Changes in the Root System of Wheat Seedlings Following Root Anaerobiosis I. Anatomy and Respiration in Triticum aestivum L.

Anatomical changes in roots of wheat seedlings (Triticum aestivumL. cv. Hatri) following oxygen deficiency in the rooting mediumwere investigated. The response of the plant to stress was testedat a very early developmental stage when the first adventitiousroots had just emerged. In order to analyze the adaptation ofdifferent roots, respiration rates of the roots 1–3 and4–n were compared with the respiration rates of the totalroot system. Oxygen deficiency was induced either by flushingnutrient solution with nitrogen or flooding of sand. In contrast to plants grown in well aerated media, both stressvariants led to a significant increase of the intercellularspace of the root cortex in seminal and first adventitious roots.Radial cell enlargement of cortical cells near the root tip,cell wall thickenings in flooded sand cultures and an increasein phloroglucinol-stainable substances were found to be furtherindicators of low oxygen supply. The roots 4–n which were promoted in growth under hypoxiashowed higher respiration rates; hence the total root respirationwas not restricted. Triticum aestivum L. cv. Hatri, wheat, roots, anatomy, anaerobiosis, stress, root respiration, intercellular space     

Changes in the Root System of Wheat Seedlings Following Root Anaerobiosis II. Morphology and Anatomy of Evolution Forms

Morphological and anatomical parameters which are variable underroot anaerobiosis in Triticum aestivum were checked on fivetaxa of primitive and modern wheats (and the related genus Aegilops).The plants were grown in nutrient solution which was eitheraerated or flushed with nitrogen. When the plants were flushedwith nitrogen a general retardation in longitudinal root growthoccurred in all of them, but only Triticum aestivum showed aclear promotion of growth of later appearing roots enablingit to maintain the same root/shoot ratio even under stress conditions.There was an increase in the volume of intercellular space inthe root cortex of nearly all the plants investigated. The diameterand the lignin content of the roots and the form of their corticalcells also varied. All these changes were expressed in the primitivewheats to a lesser extent than in the advanced Triticum aestivumindicating that there is a clear increase in the adaptive responsein the latter. Triticum species, Aegilops species, wheat, roots, anatomy, anaerobiosis, stress, intercellular space, selection     

Differences in foliage quality of young jack pine (Pinus banksiana Lamb.) on burned and clearcut sites: effects on jack pine budworm (Choristoneura pinus pinus Freeman)

Summary Suitability of young jack pine as a host for jack pine budworm was examined on similarly-aged trees growing on two areas previously burned in wildfires and on two previously clearcut areas in northwest Wisconsin. Nitrogen, monoterpenes, and moisture levels of foliage, and xylem water potential were measured and related to larval survival and pupal weight of caged jack pine budworm larvae. Nitrogen, monoterpenes, needle weight, and needle moisture were higher in trees growing on clearcut sites than on burned area trees. Surival of budworms to early and late instar, pupation, and adult eclosion was greater for larvae caged on clearcut-area trees than on burned-area trees. Female pupal weight differed between older (ca 10 years old) and younger (ca 8 years old) trees, but not between clearcut and burned areas. Mean female pupal weight was greatest on lownitrogen trees, where larval survival was lowest. Foliar nitrogen was consistently included as a significant predictor in budworm survival regressions. Regressions indicated larval survival and pupal weight may be associated with different tree- and foliage-related traits. Results suggest long-lasting effects of previous forest disturbance may subsequently affect herbivorous insects such as jack pine budworm.     

水稻无侧根突变体RM109的显微结构及其根毛形态观察

水稻原品种"大力"以NaN3诱变方法获得了稳定突变体RM109.显微结构观察表明,RM109种子根外表根毛稀少且短小,无侧根发生,而"大力"品种则有侧根发生,且密生根毛.根毛观察比较显示,距种子根根端1 cm处的RM109根毛数是"大力"品种的19%,差异极显著,根直径与"大力"品种差异不显著;距根端8 cm处的RM109根毛数和根直径分别是"大力"品种的45%和79%,二者差异极显著;距根端3 cm处,RM109最大根毛长是"大力"品种的33%,差异极显著;RM109种子根根端到根毛发生区的长度,与"大力"品种的差异不显著.