Stem-cell homeostasis and growth dynamics can be uncoupled in the Arabidopsis shoot apex

The shoot apical meristem (SAM) is a collection of stem cells that resides at the tip of each shoot and provides the cells of the shoot. It is divided into functional regions. The central zone (CZ) at the tip of the meristem is the domain of expression of the CLAVATA3 (CLV3) gene, encoding a putative ligand for a transmembrane receptor kinase, CLAVATA1, active in cells of the rib meristem (RM), located just below the CZ. We show here that CLV3 restricts its own domain of expression (the CZ) by preventing differentiation of peripheral zone cells (PZ), which surround the CZ, into CZ cells and restricts overall SAM size by a separate, long-range effect on cell division rate.     

Sound production in scolytidae:chemostimulus of sonic signal by the douglas-fir beetle

Stridulation by male Dendroctonus pseudotsugae was recorded in response to the natural female attractant (frass) or to three synthetic components of the attractant (frontalin, 3-methyl-2-cyclohexen-1-one, and trans-verbenol). This stridulation was acoustically distinct from stress sound and correlated with known attraction behavior. The response of female D. pseudotsugae to male stridulation-negation her attraction-was induced by playback of recorded attractant stridulation but not by that of stress sounds. Acoustic communication must be more important in scolytid behavior than it was heretofore believed to be.     

Elastic domains regulate growth and organogenesis in the plant shoot apical meristem

Although genetic control of morphogenesis is well established, elaboration of complex shapes requires changes in the mechanical properties of cells. In plants, the first visible sign of leaf formation is a bulge on the flank of the shoot apical meristem. Bulging results from local relaxation of cell walls, which causes them to yield to internal hydrostatic pressure. By manipulation of tissue tension in combination with quantitative live imaging and finite-element modeling, we found that the slow-growing area at the shoot tip is substantially strain-stiffened compared with surrounding fast-growing tissue. We propose that strain stiffening limits growth, restricts organ bulging, and contributes to the meristem's functional zonation. Thus, mechanical signals are not just passive readouts of gene action but feed back on morphogenesis.     

苹果离体叶片~(60)Co-γ射线辐射对不定梢再生及芽生长的影响

60Co-γ射线辐射苹果的无根无菌苗,研究了γ射线辐射对苹果叶片不定梢再生及芽生长的影响。结果表明,对辐射最敏感的器官是叶片,其次是未萌发的侧芽,第三是正在生长的顶芽。叶片不定梢再生的半致死剂量为20～30Gy,侧芽萌发的半致死剂量为30Gy。辐射剂量在10～30Gy时,抑制顶芽的伸长生长,但不引起致死或其他不良生长症状。     

不同放梢期对石硖龙眼结果母枝生长结果的影响

在南宁市和都安县龙眼产区设点，调查研究石硖龙眼9月下旬至10月底秋梢不同抽生期对结果母枝生长结果的影响。结果表明：石硖结果母枝放梢期适宜范围较大，除当年气候条件能直接影响石硖龙眼成花和坐果外，结果母株的粗度和叶面积大小等营养状况也是影响成花和坐果的重要因素之一。     

生长调节剂对‘砀山酥梨’脱萼果率和果实品质及新梢生长的影响

以‘砀山酥梨’为试材,于盛花期喷施不同浓度的保花保果剂(PBO)、多效唑(PP333)、氟硅唑(Flusilazole),研究生长调节剂对‘砀山酥梨’脱萼果率、果实品质和新梢生长的影响。结果表明:高浓度PBO、PP333虽能提高‘砀山酥梨’脱萼果率、果实固形物与可溶性糖含量,降低了有机酸含量,但使果实石细胞明显增多、硬度增加、果点增大。2 500 mg.L-1 PP333、2 000 mg.L-1 PBO处理果实石细胞含量分别为1.52%和1.47%;果肉硬度分别为6.34和6.36 kg.cm-2;果点直径分别为1.97和1.87 mm,均显著高于喷施清水对照。PBO和Flusilazole对果实品质和新梢生长影响较PP333小,花期喷施其适宜浓度为200 mg.L-1和100 mL.L-1。2 500 mg.L-1 PP333处理果点明显增大,超微结构观察表明,PP333处理使细胞排列紧凑、细胞壁变薄、木栓化程度提高,且表皮裂痕增大。     

土壤耕作层O_2含量对黄瓜各生育期根系生长特性的影响

为研究土壤耕作层不同深度O_2含量对黄瓜各生育期根系生长特性的影响,在大棚内采用不同增氧灌溉方式(A2:每2h加氧灌溉,A4:每4h加氧灌溉,A8:每8h加氧灌溉,CK:不加氧处理)对盆栽黄瓜各生育期进行增氧处理。测定土壤耕作层不同深度O_2含量和黄瓜各生育期的根系活力、根系农艺性状、根系健康指数等指标。结果表明:1)根系活力、根系农艺性状、根系健康指数等指标在黄瓜幼苗期表现为A4A2A8CK,而初花期和结瓜期表现为A2A4A8CK。2)相关性分析表明,土壤耕作层O_2含量与根系活力,根系农艺性状,根系健康指数呈显著正相关,且土壤耕作层O_2含量与根系各指标相关系数:初花期结瓜期幼苗期。由此推断,土壤耕作层O_2含量对黄瓜各生育期根系生长有重要影响,在黄瓜幼苗期适量的O_2更利于根系的生长,而在初花期和结瓜期充足的O_2能有效的促进根系生长。     

春石斛和铁皮石斛试管苗壮苗生根条件的优化

以离体保存5 a的春石斛和铁皮石斛原球茎为材料,采用正交试验对其试管苗壮苗生根的条件进行优化,从鲜重、假鳞茎、颜色、株高和根系生长等方面对植株进行综合评定.结果表明:适宜春石斛壮苗生根的培养基为1/2MS+20 g.L-1白糖+50 g·L-1香蕉匀浆物;适宜铁皮石斛壮苗生根的培养基为1/2MS+10 g·L-1白糖.     

AMF对玉米生长、根系低分子有机酸分泌与Cd累积的影响

为探讨铅锌矿区丛枝菌根真菌（Arbuscular Mycorrhizal Fungi,AMF）的生态功能,采用云南会泽铅锌矿区周边镉（Cd）污染的农田土壤,开展根袋盆栽试验,研究接种AMF对玉米生长、矿质营养、根系低分子有机酸分泌和Cd累积的影响。结果表明：接种AMF促进玉米生长,显著提高光合速率、株高和生物量;增加植株对氮、磷、钾的吸收,增幅达14.2~19.1倍;并促进根系分泌酒石酸、苹果酸、草酸和琥珀酸,分泌量增幅为1.1~3.8倍。此外,接种AMF使玉米根际铁锰氧化态Cd含量显著增加22.5%,有机结合态Cd含量显著降低12.8%,但交换态和有效态Cd含量无显著变化。接种AMF使玉米地上部和根系Cd含量显著降低,降幅分别为32.7%和77.9%,但地上部和根系Cd累积量显著增加,分别增加了12.5倍和25.8%。相关性分析发现,玉米地上部Cd累积量与草酸、酒石酸、苹果酸、琥珀酸分泌量和铁锰氧化态Cd含量呈极显著正相关。可见,AMF能促进玉米养分吸收,调节根系低分子有机酸分泌与根际Cd形态,降低植株Cd含量,从而促进植株生长。     

Paleoclimatic Inferences from Long Tree-Ring Records: Intersite comparison shows climatic anomalies that may be linked to features of the general circulation

Tree-ring data contribute to a better understanding of the nature of past climatic variations. Annual ring records several thousand years long can be constructed for a few areas, but interpretation of them requires the development of new approaches. For example, a single record of average ring width in the upper tree line environment provides a guide to past temperature fluctuations. However, comparison of this record with another, that of the arid lower forest border, from the same area permits characterization of associated precipitation and temperature anomalies that may, in turn, be linked to features of the general circulation. Other approaches that promise to be very fruitful include study of the variation of ring-width statistics through time, investigation of the physical and chemical properties of wood, and combined multivariate analysis of data for a variety of paleoclimatic indicators.     

Effect of plough pans on the growth of soybean roots in the black-soil region of northeastern China

Plough pans(PPs),common in the black-soil region of northeastern China,have significant effects on the root systems of crops. We conducted a field experiment to study the distribution of soybean roots under the influence of PPs. The soybean roots showed compensatory growth above the PP,with higher root length and weight in soil with a PP compared to those without a PP. Roots were heavier and longer in the 15–75 cm soil layer without a PP than with a PP. Soil porosity was lower in the PP and the soil below the PP,which likely decreased the oxygen content of the soil and induced more growth of roots above the PP. The PP is also likely to decrease infiltration of rain-water and hinder the migration of nitrate downward,which in turn increased the density and length of soybean root hairs,which,hence,promoted growth.     

RP-HPLC法测定不同花生根中白藜芦醇的含量

建立反相高效液相色谱法（RP-HPLC法）测定不同产地和品种花生根中白藜芦醇含量的方法。方法采用Agilent ZORBAX Eclipse XDB C18柱,以乙腈∶水（26∶74）为流动相,流速1 mL·min^-1,检测波长为303 nm,外标法定量。结果白藜芦醇在0.044～0.528μg范围内呈良好的线性关系,相关系数r=0.998,平均回收率96.95%,精密度RSD（相对标准偏差）为1.2%。结果表明该法简便,快速,适用性好。