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.

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.

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.

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.

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.

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.

杜梨组培快繁及组培苗微扦插技术研究

以种子来源的4个杜梨株系组培苗为试材,采用植物组织培养和组培苗微扦插的方法,研究了不同浓度细胞分裂素6-BA和IBA处理对杜梨丛生芽增殖的影响以及不同浓度IBA和生长素(NAA)处理对杜梨组培苗离体生根和微扦插生根的影响,以期为稳定高效杜梨组培快繁体系的建立提供参考依据。结果表明:基因型和6-BA浓度对杜梨增殖系数具有极显著影响,IBA浓度对增殖系数具有显著影响;低浓度的生长素更适合用于杜梨组培苗的生根诱导。综合考虑组培苗增殖和生根情况,DL30株系表现最优,其适宜的增殖培养基为MS+1.0 mg·L^(-1)6-BA+0.2 mg·L^(-1)IBA,增殖系数为3.4±0.35,适宜的生根培养基为1/2MS+0.2 mg·L^(-1)IBA,生根率达60.0%±20.0%。IBA和NAA蘸根处理对杜梨组培苗微扦插生根有显著影响,杜梨株系DL30组培苗通过1000 mg·L^(-1)的IBA蘸根处理后微扦插生根率为46.7%±8.8%。

苹果砧木新品种鲁砧1号离体叶片高效不定植株再生

【目的】建立苹果半矮化砧木新品种鲁砧1号离体叶片高效不定梢再生技术体系,为该砧木快繁和遗传改良奠定技术基础。【方法】以鲁砧1号无菌苗离体叶片为外植体,研究碳源、细胞分裂素种类和质量浓度对叶片不定梢再生的影响;以不定梢为试材,研究基本培养基、蔗糖质量浓度对不定梢生根的影响。【结果】MS添加较低质量浓度(0.6 mg·L^(-1))细胞分裂素(TDZ)时,碳源物质为D-山梨醇的叶片不定梢再生率显著高于蔗糖;其他激素处理下,D-山梨醇和蔗糖之间叶片不定梢再生率无显著差异。两种碳源上的平均每叶不定芽(梢)数,都表现较高细胞分裂素质量浓度处理高于或显著高于较低细胞分裂素质量浓度处理,以TDZ质量浓度为1 mg·L^(-1)时产生的不定芽数最多,平均每叶不定芽数为3.8~4个。在不定芽诱导培养基上,6-苄基氨基嘌呤(BA)比TDZ更容易诱导产生直接伸长生长的不定梢。不定梢生根率和平均每株生根条数,两种基本培养基及两个蔗糖质量浓度之间都表现差异不显著,但以1/4MS基本培养基和20 g·L^(-1)蔗糖组合的生根培养基上获得的生根率和单株生根条数最高,分别超过93%和5.8。【结论】鲁砧1号离体叶片容易诱导再生不定芽和不定梢生根,诱导叶片不定芽再生最佳培养基为MS添加1 mg·L^(-1)TDZ、0.3 mg·L^(-1)IBA和30 g·L^(-1)蔗糖,最佳生根培养基为1/4MS添加0.3~0.5 mg·L^(-1)IBA和20 g·L^(-1)蔗糖。

西南桦立木生物量模型的研建

基于2019—2020年在云南省境内采集并测定的157株西南桦立木生物量(其中地上生物量106株、全树生物量51株),建立地上、地下生物量一元(二元)独立模型W=a×D^(b)、W=a×D^(b)×HC,并采用相容性生物量模型建立西南桦地上总生物量与树枝、树叶、树干各分项生物量之和相容的西南桦立木生物量模型,采用根茎比建立地下生物量模型。结果表明:对于西南桦地上生物量,一元、二元模型分别选用权函数W=1/(D^(2))、W=1/(D^(2)H),对于西南桦地下生物量,一元、二元模型分别选用权函数W=1/(D^(0.5))、W=1/(D^(0.5)H^(0.5)),进行加权回归求解模型参数,可明显减小异方差影响及提高模型稳定性;相容性生物量模型解决了立木树枝、树叶、树干等分项生物量之和与地上总生物量不相等问题;从评价指标来看,西南桦地上总生物量和树干生物量模型预估精度均在94%以上;树枝、树叶生物量模型预估精度在92%以上,地下生物量模型预估精度在87%以上。总之,各模型预估精度均达到了国家相关精度要求;研究成果可应用于西南桦生物量的估算。

以子叶植株为砧木的大豆再生芽嫁接快繁技术

大豆组织培养过程中一直存在着再生芽不生根、生根少、根系易污染以及再生植株移栽成活率低、生长不良等问题,严重制约大豆遗传转化效率的提升。本研究针对以上问题,以只有子叶、下胚轴和根系的“子叶植株”为砧木,以组织培养产生的再生芽为接穗,建立了一种简单高效的大豆再生芽嫁接快繁技术体系。实验结果表明,以出苗后4~6 d的大豆子叶植株为砧木,以不生根、生根少或根系污染的再生芽为接穗,构建嫁接复合体,再生芽的成活率达到79.8%±4.9%。此外,将再生芽分成2~3个茎段,分别做接穗创制以子叶植株为砧木的嫁接植株,其繁殖种子总数(234.5±39.1粒)较通过组织培养系统得到的单个植株(83.7±13.2粒)提高1.8倍。综上,本研究提出的以子叶植株为砧木、再生芽为接穗的嫁接方法省去了再生芽生根过程,能够有效解决大豆组织培养过程中再生芽不生根、生根少和根系易污染等问题,提高再生芽的成活率,缩短再生芽的繁殖周期,扩大再生芽的种子产量,进而显著提高再生芽的繁殖系数。该技术对提高大豆遗传转化效率,实现再生植株的工程化快繁具有重要意义,对解决其它双子叶植物组织培养过程中再生芽生根困难问题、提高遗传转化效率也具有借鉴价值。

不同浓度矮壮素、萘乙酸和烯效唑对大葱苗期生长的影响

为探究不同植物生长调节剂对大葱苗期徒长的控制效果,研究了矮壮素、萘乙酸和烯效唑3种植物生长调节剂对大葱苗期生长的影响。结果表明,喷施3种植物生长调节剂均能显著增加大葱幼苗的根系数量、茎粗、壮苗指数和根冠比;矮壮素和烯效唑处理显著降低株高,萘乙酸处理则增加株高;矮壮素和萘乙酸处理的叶绿素含量增加,干质量增加,而喷施不同浓度烯效唑的叶片和假茎干质量在处理后35 d时分别较对照降低7.56%~31.59%和27.95%~47.33%。综合考虑大葱幼苗的形态指标和干物质分配比例,500 mg·L^(-1)烯效唑处理对大葱幼苗控制徒长的效果最好,壮苗指数和根冠比分别较对照提高111.00%和91.30%。

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.

百合斑驳病毒在卷丹顶端分生组织中的分布

【目的】百合斑驳病毒(lily mottle virus,LMoV)是危害重要食药用百合卷丹的主要病毒之一,每年给百合种植业造成数十亿的损失。通过原位杂交技术明确LMoV在卷丹顶端分生组织中的分布,为百合脱毒培养提供支撑。【方法】采用种植于贵州省清镇市的栽培卷丹作为试验材料,利用RT-PCR并于NCBI网站下载不同地方LMoV分离物构建进化树鉴定卷丹所携带的病毒种类,据检测结果选取LMoV为对象,基于LMoV基因组序列设计并制备RNA荧光探针,开展卷丹茎尖和根尖石蜡切片组织的RNA原位杂交,观察卷丹茎尖和根尖中LMoV的分布。【结果】RT-PCR检测表明卷丹材料侵染了LMoV,构建进化树发现本实验分离物与吉林和辽宁的LMoV分离物关系最近,原位杂交进而表明卷丹茎尖中LMoV杂交信号主要分布在顶端分生组织下方0.15-0.2 mm的组织中,靠近紧挨分生组织叶原基的初生叶基部有较弱的病毒杂交信号,靠近初生叶的成熟叶顶端中病毒荧光信号强烈,感染LMoV的卷丹分生组织中心纵切面无毒区大小为(0.4-0.6)mm×(0.15-0.2)mm;在根尖0.25 mm×0.2 mm分生组织中无杂交信号分布,在皮层细胞中信号最强烈,在根冠和根伸长区信号较弱。【结论】卷丹顶端分生组织及最接近顶端的一个叶原基[大小约(0.4-0.6)mm×0.2 mm]未发现病毒信号,可作为茎尖脱毒的起始材料。根顶端分生组织外侧根冠有较强病毒信号,不适合作为卷丹脱毒培养的外植体。

播期推迟对棉花根系生长发育特征及产量的影响

【目的】研究推迟播期对棉花根系生长发育特征和产量的影响,为黄河流域棉区棉花适期播种提供依据。【方法】2022―2023年在河北农业大学威县试验站开展田间试验,设置常规播期(4月15日)和推迟播期(5月1日)2个处理,分析推迟播期对棉花品种冀农大23号的根系分布、根系生长速率、根冠比、干物质积累量和产量等的影响。【结果】与常规播期相比,推迟播期条件下,棉花根系长度和生物量的最大增长速率分别增加2.92~5.35 cm·d^(-1)和0.40~0.76 mg·d^(-1);深层土壤中棉花根系占比提高,其中30~60 cm土层根系长度占比和根系生物量占比分别增加2.99~3.55百分点和3.94~4.42百分点;生育后期棉株地上部干物质积累量和根冠比无明显差异;根系载荷能力显著降低6.43%~17.69%;2022年籽棉产量无显著差异,2023年单位面积铃数和籽棉产量分别显著增加9.72%和7.66%。相关分析表明,0~60 cm土层根长密度、0~60 cm土层根系生物量密度、根系生物量最大增长速率和30~60 cm土层根系长度占比均与籽棉产量极显著正相关。【结论】黄河流域棉区推迟播期(5月1日)可通过提高棉花根系生长速率、深层土壤中根系长度和根系生物量的占比,增强根系吸收功能以保障地上部干物质的积累,促进棉花高产。

不同品种玉米根-冠生长对土壤紧实胁迫的差异性响应特征

黄淮海地区农业集约化和机械化发展导致土壤紧实问题日益加重,限制玉米产量的进一步提升。明确不同品种玉米根系和地上部生长对土壤紧实胁迫的差异性响应特征,可为该区玉米高产栽培提供理论依据。本研究选用3个玉米品种,采用机械碾压的方法在同一田块模拟无紧实胁迫(NC:no compaction stress,容重1.0~1.3 g cm^(-3))、中度紧实胁迫(MC:moderate compaction stress,容重1.4~1.5 g cm^(-3))和重度紧实胁迫(HC:heavy compaction stress,容重>1.6 g cm^(-3))3个紧实程度处理,定量解析不同程度土壤紧实胁迫下不同品种玉米根冠生长各指标及产量的变化规律。结果表明,与NC相比,MC和HC处理导致玉米减产3.8%~10.3%和12.5%~33.3%。玉米根冠生长及产量形成对土壤紧实胁迫的响应存在基因型差异。MC处理下,DK517的根长、根干重及根冠比较ZD958和DH605分别提高6.0%和14.0%、15.7%和29.6%、18.8%和24.8%,但最大叶面积指数、植株总干物重和产量无显著差异;HC处理下,DK517的根长和根干重较ZD958和DH605分别提高8.4%和22.5%、29.6%和57.8%,且最大叶面积指数、植株总干物重和根冠比分别提高4.6%和15.5%、3.7%和20.9%、28.0%和32.1%,因此产量分别增加7.5%和27.2%。相关分析表明,土壤容重和贯穿阻力与玉米根冠生长各指标和产量呈显著负相关关系(P<0.01)。综上所述,土壤紧实胁迫会显著抑制玉米根系和地上部生长而造成减产,但不同品种玉米根冠生长对不同程度土壤紧实胁迫的响应存在着差异,重度土壤紧实胁迫下根冠生长均具有优势的品种能够维持较高的产量,研究结果可为玉米品种改良和土壤紧实下耕作措施优化提供理论依据。

光竞争对杉木幼苗生长、生物量分配及叶片化学计量特征的影响

通过研究杉木幼苗在不同光竞争条件下的生长特性及叶片C、N、P化学计量响应策略,以探究光竞争环境下杉木叶片营养利用及生长适应性规律。选择生长均一杉木无性系幼苗,采用室内盆栽试验,通过调整相邻盆栽容器高度差以模拟相邻杉木获得不同光资源优势,形成具有明显光资源竞争优势植株(优势木)及竞争劣势的相邻植株(竞争木),根据调整后的高度差共设置3个光竞争强度:强度光竞争(高度差0 cm)、中度光竞争(高度差8 cm)、轻度光竞争(高度差16 cm),通过测定分析光竞争模拟处理1 a后参试幼苗苗高和地径、各器官生物量以及叶片C、N、P含量的差异性,分析各元素间化学计量比特征。结果表明,随着光竞争强度的减小,竞争木苗高比优势木高6.04%,地径比优势木小17.51%,根冠比增大,根系生物量分配比例增大至40.0%。随着光竞争强度的减小,竞争木植株叶片N含量增多达21.63 g/kg;优势木叶片C、P含量变化趋势相同,均随光竞争强度的减小先减小后增大,且显著大于竞争木(P<0.05);优势木C/N、C/P均随着光竞争强度的减小先增大后减小,竞争木C/P随光竞争强度的减小而增大。优势木叶生物量与P含量呈显著正相关,竞争木茎生物量与叶生物量呈显著正相关,与P含量呈显著正相关。不同光资源竞争位置杉木幼苗生长特性及叶片化学计量特征对不同光竞争强度适应策略有差异,表现为随光竞争强度的减小,处于光竞争劣势的竞争木生物量主要分配于地下根系,幼苗株形呈现“细高”的生长趋势;与之相反,光资源竞争的优势木则将生物量分配倾向于叶片,同时C、P含量明显减小,株形呈现“矮粗”的生长趋势。

祁连山北麓荒漠草原5种优势植物生物量与土壤养分特征

为明晰荒漠草原优势植物的植物生物量与土壤养分关系,研究选取祁连山北麓肃北区域荒漠草原骆驼蓬(Peganum harmala)、狗尾草(Setaria viridis)、中华羊茅(Festuca sinensis)、碱茅(Pucci-nellia distans)和冰草(Agropyron cristatum)5种优势植物,测定该其生物量和根际土壤养分,探究其植物生物量分配及其与土壤养分间的关系。结果表明:(1)5种优势植物间总生物量和根冠比差异显著(P<0.05),骆驼蓬总生物量最高,碱茅最低。多年生的骆驼蓬、碱茅、中华羊茅和冰草植物生物量大部分集中在地下,一年生的狗尾草植物生物量大部分集中在地上,不同植物间根冠比大小为:碱茅>冰草>中华羊茅>骆驼蓬>狗尾草。(2)5种植物根际土壤有机碳、碱解氮、速效钾、全氮、全磷、全钾及其化学计量特征均存在显著差异(P<0.05),5种植物根际间土壤碳氮比大小为碱茅>狗尾草>冰草>骆驼蓬>中华羊茅。(3)不同植物生物量、根冠比及土壤养分变异性不一致,骆驼蓬、狗尾草和中华羊茅的根际土壤全钾与碱茅和冰草的根际土壤含水量等均为弱变异,而土壤养分及其化学计量特征为中等变异。5种优势植物的生物量与根际土壤碱解氮和全钾呈正相关性(P<0.05)。可见荒漠草原生态系统中植物生物量分配和根际土壤养分在生活史和物种间的差异较大,今后应根据不同优势植物养分需求,合理施肥来修复退化的荒漠生态系统。

6种阔叶树种幼苗生物量分配特征及模型构建

以福建省上杭白砂国有林场闽楠、南岭栲、米老排、青冈、云山青冈和木荷2年生幼苗为研究对象,采用全株收获法获取6种树种幼苗根、茎、叶及整株的生物量,比较其分配特征和地上、地下生物量的异速生长关系,建立不同树种幼苗各器官及整株生物量的回归估测模型。结果表明:(1)不同树种幼苗整株生物量差异显著,依次为青冈>米老排>南岭栲>云山青冈>木荷>闽楠。(2)不同树种幼苗各器官生物量分配差异显著,其中青冈根生物量占比最大(39.9%),米老排茎生物量占比最大(45.0%),闽楠叶生物量占比最大(49.2%)。(3)不同树种幼苗地下生物量与地上生物量比值均小于1,表明幼苗生物量更多地分配到茎和叶。除木荷外,其余树种地上、地下生物量均遵循显著的等速生长关系。(4)不同树种幼苗生物量回归估测模型多为幂函数模型,其次为三次多项式模型。6种树种幼苗整株生物量在不同器官分配上存在差异,同时幼苗地上、地下生物量间呈现出等速生长规律。各树种幼苗生物量回归估测模型拟合效果较好,可在相同或相似立地条件下估算不同树种幼苗生物量。

施氮对紫花苜蓿干旱复水后生长恢复能力的影响

植物复水后的生长恢复能力是体现植物干旱适应性的重要方面。施氮是常见的栽培措施,但施氮对紫花苜蓿(Medicago sativa)复水后生长恢复能力的影响尚不明晰。本研究在低氮(3 mmol·L^(−1))和高氮(7 mmol·L^(−1))处理下对紫花苜蓿进行水培,在培养液中添加聚乙二醇-6000模拟干旱-复水情况,在干旱结束当天、复水7 d以及24 d,测定紫花苜蓿地上和地下部的生物量、含氮量、非结构性碳水化合物以及相关酶活性。结果显示,复水24 d时,高氮处理的总生物量高于对照组(未受干旱处理)11.0%,发生了“补偿生长”,而低氮处理的生长尚未恢复,生物量低于对照组19.6%。由于“干旱记忆”,复水7 d以及24 d时,高氮处理的根冠比、根系中淀粉和可溶性糖含量显著增加(P<0.05),而低氮处理则无显著变化(P>0.05)。复水7 d,高氮下紫花苜蓿叶片蔗糖磷酸合成酶(SPS)活性下降,而蔗糖合成酶(SS)和根中酸性转化酶(AI)活性显著提高(P<0.05)。复水24 d时,与低氮处理相比,高氮处理更明显地提高了SS活性(P<0.05)。结果表明,施氮通过增强植物叶片SS酶活性,提高根系干物质、淀粉和可溶性糖的积累,从而增强紫花苜蓿复水后的生长恢复能力。