Establishment of highly efficient plant regeneration of Paeonia ostii‘Fengdan’through optimization of callus,adventitious shoot,and rooting induction

Tree peony is a famous ornamental plant,while the low propagation rate is the main hurdles hindering the industry development.Till now,the highly efficient regeneration system for tree peony is not established.In this study,using Paeonia ostii’Fengdan’mature embryos,the effects of variations in inoculation method,initiating culture,adventitious shoot induction,rooting media,plant growth regulators(PGRs),and a nonconventional PGR(plant extracts)on regeneration from explants were evaluated.In embryo cultures,embryonic callus induction rate of 1/4 embryos was the highest among those of embryos with other three technical treatments(whole embryos,1/2 embryos,and pieces of embryos).The woody plant medium(WPM)containing 1.0 mg·L^(-1)6-BA,0.5 mg·L^(-1)GA3,30.0 g·L^(-1)sucrose,and 3.0 g·L^(-1)phytagel significantly improved shoot induction and multiplication.3.0 mg·L^(-1)plant extracts promoted hypocotyl germination,rooting,and root growth,in direct embryo culture,and a combination of 3.0 mg·L^(-1)plant extracts+2.0 mg·L^(-1)IBA+1.5 mg·L^(-1)IAA produced optimal rooting induction rate for multiple shoots in direct embryo culture and indirect somatic embryogenesis.For the three in vitro micropropagation methods,the highest shoot proliferation coefficient(5.4±0.2)was obtained with indirect somatic embryogenesis.Fortunately,the propagation ability of shoots remains high,even when culture propagation was continued for more than two years.Thus,a reliable system for plant regeneration from mature embryos derived from P.ostii’Fengdan’callus and two direct embryo culture systems have been established.The novel regeneration system could facilitate uniform seedling production.

Does the root to shoot ratio show a hormetic response to stress? An ecological and environmental perspective

Root/shoot(R/S)ratio is an important index for assessing plant health,and has received increased attention in the last decades as a sensitive indicator of plant stress induced by chemical or physical agents.The R/S ratio has been discussed in the context of ecological theory and its potential importance in ecological succession,where species follow different strategies for above-ground growth for light or below-ground competition for water and nutrients.We present evidence showing the R/S ratio follows a biphasic dose–response relationship under stress,typical of hormesis.The R/S ratio in response to stress has been widely compared among species and ecological succession classes.It is constrained by a variety of factors such as ontogeny.Furthermore,the current literature lacks dose-response studies incorporating the full dose–response continuum,hence limiting scientific understanding and possible valuable application.The data presented provide an important perspective for new-generation studies that can advance current ecological understanding and improve carbon storage estimates by R/S ratio considerations.Hormetic response of the R/S ratio can have an important role in forestry for producing seedlings with desired characteristics to achieve maximum health/productivity and resilience under plantation conditions.

Regulation of phytohormones on root primordium initiation and adventitious root formation in the etiolated shoots of Paeonia suffruticosa'Yinfen Jinlin'

Tree peony is well known and sought after for its large, colorful flowers. Its propagation is via vegetative methods. Mech- nisms of the adventitious rooting and the regulation of rooting processes are the principles and techniques of plant propagation and improvement. Microstructures and fluctuations of phytohormones in the adventitious rooting were studied with the etiolated soft- wood shoots of Paeonia suffkuticosa ＇Yinfen Jinlin＇. There are no pre-primordia in the shoots of the cultivar. Adventitious roots are produced in five stages： shoot selection, primordium initiation, primordium growth, conducting tissue differentiation and root protru- sion. Primordia initiated in the cortex. The contents of the endogenous hormones, IAA, ABA and GA, were 5.842, 0.873 and 1.043 nmol·g^-1 FW on the bases of shoots, respectively. CTKs which included isopentenyl adenine （iPA）, zeatin riboside （ZR） and dihy- drozeatin riboside （DHZR） were 0.949, 0.695 and 2.034 nmol·g^-1 FW, respectively. DHZR is active among CTKs. The ratio of IAA to GA, CTK and ABA clearly increased at the stage of primordium initiation, while they showed low levels at the stages of primor- dium growth. The ratios were restored at the shoot levels at the stage of root protrusion. IBA provoked primordia initiation in the cortex, the vascular cambium, the pith and even in the callus induced on the base of shoots. ]AA levels in the treated shoots increased gradually to its highest level （three times of control） at the stage of conducting tissue differentiation. The ratios of IAA to GA, CTK and ABA clearly decreased at the stage of primordium initiation. The ratio of IAA to ABA is regulated at 10：1.

Water Deficit Stress Effects on Corn (<i>Zea mays</i>, L.) Root:Shoot Ratio

A study was conducted at Akron, CO, USA, on a Weld silt loam in 2004 to quantify the effects of water deficit stress on corn (Zea mays, L.) root and shoot biomass. Corn plants were grown under a range of soil bulk density and water conditions caused by previous tillage, crop rotation, and irrigation management. Water deficit stress (Dstress) was quantified by the number of days when the water content in the surface 0.3 m deviated from the water content range determined by the Least Limiting Water Range (LLWR). Root and shoot samples were collected at the V6, V12, and R1 growth stages. There was no significant correlation between Dstress and shoot or root biomass at the V6 growth stage. At the V12 and R1 growth stages, there were negative, linear correlations among Dstress and both root biomass and shoot biomass. The proportional decrease of shoot biomass was greater than the proportional decrease in root biomass, leading to an increase in the root:shoot ratio as water deficit stress increased at all growth stages. Determining restrictive soil conditions using the LLWR may be useful for evaluating improvement or degradation of the soil physical environment caused by soil management.

The Equilibrium and Growth Stability of Winter Wheat Root and Shoot Under Different Soil Water Conditions

The equilibrium between root, shoot and growth stability under different soil water conditions were investigated in a tube experiment of winter wheat. The water supplying treatments included： sufficient irrigation at whole growth phase, moderate deficiency irrigation at whole growth phase, serious deficiency irrigation at whole growth phase, sufficient irrigation at jointing stage, tillering stage, flowering stage, and fillering respectively, after moderate and serious water deficit during their previous growth stage. Root and shoot biomass were measured. On the basis of the cooperative root-shoot interactions model, the equilibrium and growth stability were studied on the strength of the kinetics system theory. There was only one varying equilibrium point between the root and shoot over the life time of the winter wheat plant. Water stress prolonged the duration of stable growth, the more serious the water deficit, the longer the period of stable growth. The duration of stable growth was shortened and that of unstable growth was prolonged after water recovery. The growth behavior of the plants exposed to moderate water deficit shifted from stable to unstable until the end of the growth, after rewatering at flowering. In the life-time of the crop, the root and shoot had been adjusting themselves in structure and function so as to maintain an equilibrium, but could not achieve the equilibrium state for long. They were always in an unbalanced state from the beginning to the end of growth. This was the essence of root-shoot equilibrium. Water stress inhibited the function of root and shoot, reduced root shoot interactions, and as a result, the plant growth gradually tended to stabilize. Rewatering enhanced root shoot interactions, prolonged duration of instable growth. Rewatering at flowering could upset the inherent relativity during the long time of stable growth from flowering to filling stage, thus leading to unstable growth and enhanced dry matter accumulating rate in the whole plant.

Effects of Soil Moisture on Dynamic Distribution of Dry Matter Between Winter Wheat Root and Shoot

The dynamic relationship of dry matter accumulation and distribution between winter wheat root and shoot was studied under different soil water conditions. The dry matter accumulation in root was greatly influenced by water stress, so as to the final root weight of the treatment with 40% field moisture capacity(FMC) was less than 1/4 of that of the treatment with 80% FMC on average. Water stress during the 3-leaf stage to the tillering stage had the greatest influence on root, and the influence of water stress during the jointing stage to the booting stage on shoot was greater than root. However, water stress during the tillering stage to the booting stage had a balanced effect on root and shoot, and the proportion of dry matter that distributed to root and shoot was almost the same after rewatering. Water recovery during the jointing stage to booting stage could promote R/S, but the increasing degree was related to the duration of water limitation. Soil water condition had the lowest effect on R/S during the flowering stage to the filling stage and the maximal effect on R/S during the jointing stage to the heading stage, R/S of 40% FMC treatment was 20.93 and 126.09% higher than that of 60% FMC and 80% FMC treatments respectively at this period.

Direct Regeneration of Plants Derived from in vitro Cultured Shoot Tips and Leaves of Poplar （Populus×euramericana ＇Neva＇）

The purpose of the present study was to establish a regeneration procedure for Populus × euramericana ＇Neva＇ by using in vitro shoots tips and leaves. For sterilization, 0.1% （w/v） mercuric chloride （HgCl2） solution for 8 to 10 min was the optimal treatment for this poplar cultivation. The effects of benzyladenine （BA） and α-naphthaleneacetic acid （NAA） added to Murashige and Skoog （MS） medium were tested on organogenesis. The highest regeneration rate and numbers of shoots/explant from shoot tips （96.7%, 9.8） and leaves （90.0%, 8.7） were obtained on the half-strength MS medium supplemented with 0.5 mg/L BA and 0.1 mg/L NAA. The optimal medium for in vitro rooting of shoots was on a half-strength MS medium containing 1 mg/L indolebutyric acid （IBA） with the highest rooting frequency （93.3%） and numbers of roots/explant （8.2）. For acclimatization, in vitro rooted plantlets were transferred to plastic cups containing vermiculite and peat （1： 1）. After acclimatization, transplanted plantlets grew well in a shade house. Therefore, we believe that this efficient plant regeneration protocol especially by leaf explants is very important for in vitro clonal propagation of Populus×euramericana ＇Neva＇.

Root-shoot relationships of Fraxinus mandchurica

In this paper, root-shoot relationships of seedlings of Manchurican ash (Fraxinus mandchurica) in pots is studied in green house. The results show that roots and shoots have the co-ordination of growth and roots and shoots of ash have the same growth dynamics. There are very close relationships between toall root mass and total shoot mass, between fine root mass and leaf mass in this experiments. At the end growing season, ash root-shoot mass ratio and fine root-leaf mass ratio are 1 .85 and 2.01 respectively. These ratios are difference during growth season. There are larger roots than shoots on seedling stage. Low nitrogen and phosphorus produce higher root-shoot ratio, and high nutrient concentrations decrease the ratios.

Variations in shoot and root growth of three provenances of Faidherbia albida in clay and sand soil

The variation in shoot and root seedling growth traits was compared among three Faidherbia albida （Del）. A. Chev. provenances originating from Kenya （Taveta）, Malawi （Bolero） and Ghana （Bolgatanga）; representing east, south and west Africa, respectively. Bulked seeds from three provenances were grown in two soil types （clay and sand） at the World Agroforestry Centre nursery, Nairobi. Seedlings grown in clay soil had high shoot growth and shoot to root ratios but shorter root length, lower number of nodules and specific root length compared to seedlings in sand soil. Shoot to root ratios reduced with time and this was more pronounced in sand soil. Overall, the Bolero and Taveta provenances had higher growth than the Bolgatanga provenance. This was probably because plants grown in nutrient-rich clay soil invest more in shoot growth as compared to root growth. Longer root growth in sand soil shows a better adaptive mechanism that increases competitive ability and survival in nutrient-poor systems. Variations observed among the seedling variables such us shoot and root growth could be used for early selection for reforestation and agroforestry in predominantly clay and sand soil areas.

Phytohormones Accumulation and Distribution in Shoots and Roots of Haploid,Diploid and Tetraploid Barley Seedlings Derived from Microspore Culture

Phytohormones play important roles in plant growth and development,and polyploids are thought to be an important method for plant breeding.However,the relationship between ploidy and phytohormone is still unclear.In this study,barley at three ploidy levels were produced by microspore culture.Therefore,we further analyzed the phytohormone content in the shoots and roots of the three kinds of barley materials to study the effect of ploidy on phytohormones accumulation and distribution.The results showed that Abscisic acid(ABA),gibberellin(GA),jasmonic acid(JA),auxin(IAA),salicylic acid(SA)and cytokinin(CTK)were successfully determined in shoots and roots using LC-MS(liquid chromatography mass spectrometry).By comparing the shoots of the haploid and diploid plants,it was found that the distribution trend of the six phytohormones was consistent,and another consistent trend was found in the roots of the diploid and tetraploid plants.In addition,we further analyzed the shoot/root ratio of the different phytohormones to identify the potential differences for haploid,diploid and tetraploid.Here,the relationship between ploidy and phytohormone we provided would provide new insights into understanding the new phenotypes that occur in polyploid species.

Establishment of Somatic Cell Clones in Thesium chinense Turcz and Its in vitro Rooting Technique

[Objective] The aim of this study is to establish the rapid micro-propagation system in Thesium chinense Turcz.[Method]With stem fragments of wild Thesium chinense Turcz as explants,different culture media were designed to conduct induction culture,strengthening plantlet culture and in vitro rooting.[Result]The optimum medium for inducing clustered shoots was determined to be MS medium appended with 1.5 mg/L 6-BA,0.01 mg/L NAA and 0.3 mg/L 2,4-D;in addition,60 mg/kg ABT was suitable for rooting,by which the percentage of rooted plantlets reached 76.6%.[Conclusion]This study simplified the procedures of tissue culture in Thesium chinense Turcz and enhanced the proliferation rate,providing basis for artificial cultivation and resource protection of Thesium chinense Turcz.

多花胡枝子超嫩梢扦插繁殖及生根机理研究

探究植物生长调节剂对多花胡枝子超嫩梢扦插生根效果与内源激素含量变化的影响,揭示多花胡枝子超嫩梢扦插繁殖的生根机理。以多花胡枝子顶部嫩梢为材料,测定植物生长调节剂种类、浓度对多花胡枝子扦插生根率、生长及内源激素含量的影响。结果表明,多花胡枝子超嫩梢扦插生根类型为愈伤组织生根;生根过程经历愈伤组织阶段、不定根形成阶段和不定根伸长阶段;T5处理的插穗表现出最佳效果,生根率为100%。插穗内源激素与生根密切相关,与CK相比,处理组IAA与GA的含量较高,且IAA/ABA与IAA/ZR的含量比值较高,ABA与ZR的含量较低,经过植物生长调节剂处理后,有利于多花胡枝子超嫩梢扦插生根。研究获得了多花胡枝子超嫩梢扦插生根的最适宜处理,T5处理下有利于一级根生长,促进扦插苗的生长,提高IAA含量及其与ABA、ZR的比值,有利于多花胡枝子超嫩梢扦插生根。

A Comparative Study of Morphological Responses of Seedling Roots to Drying Soil in 20 Species from Different Habitats

Rooting depth and root and shoot biomass were measured for seedlings of 20 species in both watered and unwatered sand columns. The species were from habitats of widely varying moisture status, ranging from marsh to desert. Moisture status of the species' habitats was quantified as Ellenberg moisture number. Seedlings were allowed to grow in moist sand for 21 days and were then exposed to the treatments (watered and unwatered) for a further 21 days. Rooting depth of control plants was not correlated with Ellenberg number. Root depth of plants from dry habitats tended to increase in drying sand, while roots of plants from wet habitats decreased in depth. Plasticity of rooting depth (depth in unwatered / depth in watered sand) was significantly correlated with Ellenberg number ( r 2 = 0.56). Plasticity of shoot/root ratio was also correlated with Ellenberg number, but the relationship was weaker than for rooting depth plasticity. Species that showed the greatest plasticity in rooting depth also showed the greatest ability to sustain shoot growth in unwatered sand. There was some evidence that growth of plants from very dry habitats was reduced in the watered treatment. Results of this study suggest that a major, although not the only, adaptation of plants of dry habitats is the ability of their seedlings to exploit deeply buried water resources.

Study on the Influencing Factors and the Root Mechanism in Cutting Process of Prunus humilis(Bge). Sok

A procedure for cutting Prunus humilis（Bge）. Sok was comprehensively studied in this paper. It was found that the key factors involved in this procession were medium, rooting accelerator, concentration of rooting accelerator and type of shoot. The results showed that send was used as mediums; Treatment with 1 000 mg/L AST rooting powder No. 2 and semi-woody shoots were the optimal materials for cutting, and the rooting rate reached 88.1%. Anatomical study on rooting of Prunus hum#is（Bge）. Sok cutting has been carded out by the paraffin section method. The observation result shows that the adventitious root primordium of Prunus humili$（Bge）. Sok cutting belongs to the type of induced root primordium. The adventitiousroot primordium originates from the cross region of vascular cambium and pith rays.

The Role of Nitrogen Fertilizers in Sugarcane Root Biomass under Field Conditions

Sugarcane is used worldwide for sugar, ethanol and energy production. In Brazil, the shift from burned to unburned harvest systems resulted in increases in nitrogen fertilization rates, which can impact root architecture and biomass. The expectation is also an increase in sugarcane biomass. The study hypothesized that high N rates applied to sugarcane fields increases root growth and N stored in roots, promoting higher biomass and N accumulated in shoots. Two experiments were set up in Southeastern Brazil, on a Typic Kandiudox (TK) and Rhodic Eutrudox (RE). Four treatments were studied 1) N application in the plant-cane (0 and 120 kg·ha-1 N) and 2) N application in the ratoon (0 and 150 kg·ha-1 N). The shoot biomass and the root density (by the core method up to 0.6 m) were evaluated over the first ratoon crop cycle, and the N content in those compartments was also examined. There was no carry over effect on N applied at planting in root and shoot biomass in the ratoon crop cycle. At the RE site, the ratoon N fertilization increased root density in the superficial soil layer (0 - 0.2 m) and close to the plants (<0.3 m). The effect of N addition on root biomass, and biomass and N accumulated in shoot was limited in both sites. Increasing N rates in unburned sugarcane fields do not consistently increases root and shoot biomass under Brazilian field conditions.

Root distribution of three co-occurring desert shrubs and their physiological response to precipitation

Root distribution of three desert shrubs,Tamarix ramosissima Ledeb.,Haloxylon ammodendron(C.A.Mey.) Bunge and Reaumuria soongorica(Pall.) Maxim.was investigated under co-occurring conditions using a method for excavating the whole root system.Assimilation shoot water potential and transpiration rates were monitored during the wet-dry cycle.Leaf-specific apparent hydraulic conductance and the index of water stress impact for the three species were calculated from shoot water potential and transpiration rate.The results showed that,along the soil profile,the root system of T.ramosissima mainly distributed at 50 to 310 cm interval,with an average total absorbing root-surface area of 30,249.2 cm2 per plant;the root system of H.ammodendraom distributed at 0 to 250 cm interval with an average total absorbing root-surface area of 12,847.3 cm2 per plant;the root system of R.soongorica distributed at 0-80 cm interval,with an average total absorbing root-surface area of 361.8 cm2.The root distribution shows the following:T.ramosissima uses groundwater as its main water source;H.ammodendraom uses both groundwater and rainwater;and R.soongorica uses rainwater only.During the wet-dry cycle,the hydraulic parameters of T.ramosissima showed no responses to precipitation.R.soongorica responded most significantly,and the responses of H.ammodendraom were intermediate.In conclusion,the plant response to rain events is closely related to their root distribution and plant water-use strategy.

Non-aerated liquid culture promotes shoot organogenesis in Eucalyptus globulus Labill

Eucalyptus is very recalcitrant to in vitro culture.In this research, an efficient shoot organogenesis system was developed using 60-day-old plants of Eucalyptus globulus grown in vitro and non-aerated liquid medium to improve shoot proliferation. Cultures were initiated with hypocotyls and leaf segments from plantlets cultivated on semisolid 1/2 MS modified medium supplemented with 4.44 μM 6-Benzyladenine(BA) and 16.1 μM 1-Naphthaleneacetic acid(NAA). Calli were transferred to shoot induction medium, with either 0.5 or 2.7 μM NAA. Shoot multiplication was carried out on 4.44 μM BA + 0.5 μM NAA medium, and semisolid and non-aerated liquid systems were compared for improving shoot proliferation.Rooting of adventitious shoots was evaluated on medium containing NAA or Indole-3-butyric acid-IBA(5 and16 μM). Callogenesis was obtained from both types of explants, although shoot formation was only obtained from leaf-derived calli. Shoot proliferation on 4.44 μM BA+0.5 μM NAA resulted in the most shoots/callus.Non-aerated liquid medium was more efficient in promoting shoot multiplication(53.5 shoots/callus) than was semisolid medium(28.5 shoots/callus). Levels of phenolic compounds were significantly reduced in the shoots cultivated in liquid medium. Efficient rooting(76%) was obtained using 16 μM IBA.

Effects of cutting types and hormonal concentration on vegetative propagation of Zanthoxylum armatum in Garhwal Himalaya,India

Experiments were carried out to define the effects of hormonal concentrations on semi-hard wood（SHW） and hard-wood（HW） branch cuttings of the Z.armatum. SHW and HW cuttings were collected in the month of March. The SHW and HW cuttings were treated with different concentration of indole-3-acetic acid and indole-3-butyric acid（IAA and IBA） and placed in vermiculite rooting medium for 90 days under 1-min misting after 10 min. Sprouting, rooting percentage, sprout number, sprout length, root number, and length were measured.The highest rooting and sprouting rate, 64.0 %, was obtained at the 0.3 % IBA treatment in the SHW cuttings.Similarly sprout length and number of roots per cutting were also higher at the 0.3 % IBA treatment in the SHW cuttings. The number of shoots per cutting was higher at the 0.3 % IAA treatment in the SHW cuttings. Root length per cutting was higher in 0.4 % IBA treatment in the SHW cuttings. The results indicated that 0.3 and 0.4 % IBA treatment produce higher rooting percentages as well as the number of roots and their length in SHW cuttings. The HW cuttings produced maximum rate of 18.0 % rooting in0.5 % IBA treatment. The control set and lower concentrations of IBA and IAA completely failed to root in the mist chamber.

Water adaptive traits of deep-rooted C_3 halophyte(Karelinia caspica(Pall.) Less.) and shallow-rooted C_4 halophyte(Atriplex tatarica L.) in an arid region,Northwest China

This paper focused on the water relations of two halophytes differing in photosynthetic pathway, phe- notype, and life cycle： Karelinia caspica （Pall.） Less. （C3, deep-rooted perennial Asteraceae grass） and Atriplex tatarica L. （C4, shallow-rooted annual Chenopodiaceae grass）. Gas exchange, leaf water potential, and growth characteristics were investigated in two growing seasons in an arid area of Xinjiang to explore the physiological adaptability of the two halophytes. Both K. caspica and A. tatarica showed midday depression of transpiration, in- dicating that they were strong xerophytes and weak midday depression types. The roots of A. tatarica were con- centrated mainly in the 0-60 cm soil layer, and the leaf water potential （~L） increased sharply in the 0-20 cm layer due to high soil water content, suggesting that the upper soil was the main water source. On the other hand, K. caspica had a rooting depth of about 1.5 m and a larger root/shoot ratio, which confirmed that this species uptakes water mainly from deeper soil layer. Although A. tatarica had lower transpiration water consumption, higher water use efficiency （WUE）, and less water demand at the same leaf water potential, it showed larger water stress impact than K. caspica, indicating that the growth of A. tatarica was restricted more than that of K. caspica when there was no rainfall recharge. As a shallow-rooted C4 species, A. tatarica displayed lower stomatal conductance, which could to some extent reduce transpiration water loss and maintain leaf water potential steadily. In contrast, the deep-rooted C3 species K. caspica had a larger root/shoot ratio that was in favor of exploiting groundwater. We concluded that C3 species （K. caspica） tapes water and C4 species （A. tatarica） reduces water loss to survive in the arid and saline conditions. The results provided a case for the phenotype theory of Schwinning and Ehleringer on halophytic plants.

Potential of Plant Growth Regulators on Modulating Rooting of <i>Rosa centifolia</i>

Rosa centifolia is grown for its flowers which are used for essential oil extraction. It is vegetatively propagated through its cuttings which are difficult to root. This study was designed to increase the rooting percentage of cuttings by applying plant growth regulators (PGRs) with different levels. In total 31 treatments with different concentrations (450 ppm, 700 ppm and 950 ppm) of indole butyric acid (IBA), indole acetic acid (IAA), naphthalene acetic acid (NAA) alone, in combination and with same concentrations of 6-benzylamino purine (BAP) were used. Healthy similar sized cutting of R. centifolia was treated in solution of PGRs by quick dip method and planted in polythene bags. The data for shoot length, shoot dry weight, number of roots, root length and root dry weight were recorded. All three levels (450 ppm, 700 ppm and 950 ppm) of IBA alone produced maximum results in case of all parameters as compared to all other treatments. Among three levels of IBA, 450 ppm concentration produced maximum shoot length (10.67 cm), shoot dry weight (3.02 g), number of roots (14.00), root length (11.90 cm) and root dry weight (0.50 g). Lower concentrations of plant growth regulators produced better results as compared to higher concentrations.