Hydroxyurea-induced mitotic synchronization in Allium sativum root meristems

The synchronized divisions following a treatment with hydroxyurea (HU) — an inhibitor of DNA synthesis — were studied in root meristems of Allium sativum using two methods: autoradiography of median sections and morphological labeling with a cytokinesis inhibitor. It is shown that the second wave of mitoses is heterogeneous: it is composed mostly of cells which have been synchronized in the S phase by the HU treatment, of cells coming from the quiescent center stimulated to enter DNA synthesis and of cells which were not blocked by the 23 h HU treatment (slow cycling cells). It is also shown that the cell cycle following the first synchronized division is considerably shortened by the synchronization procedure.Abbreviations QC quiescent center - HU hydroxyurea - MHQD methyl-3 hydroxy-6 quinazoline dione 2–4     

The influence of 5-aminouracil on the mitotic index of barley root meristems

Isolated barley embryos were cultivated in the complete liquid medium for 24 h and then treated with 200 ppm or 750 ppm 5-AU for 2 h, 8 h or 24 h. During the 24 h treatment, MI decreased from 5–12% to 2–5%. After putting the embryos into the fresh medium without 5-AU, the original decrease of MI was followed by slight increase which was manifested only in part of the roots of some experimental variants. The time of the occurrence of MI maxima varied with the duration of treatment and concentration of 5-AU. After treatment with 750 ppm, the increase of MI occurred later but it was more pronounced than after cessation of the treatment with 200 ppm. In the former case, frequencies exceeding the controls appeared 12 h–16 h after treatment and they were manifested especially after treatments of shorter durations (2 h and 8 h). In the latter case, the increase of MI occurred mainly 6 h after cessation of the 24 h treatment. A slight chromosome breaking ability of this drug was found.     

Effect of oryzalin on root ultrastructure and respiration in various wheat cultivars subjected to cold hardening

The effect of anti-microtubular herbicide oryzalin (10 μM, 2–4 days) on the root ultrastructure and respiration in two cultivars of winter wheat (Triticum aestivum L.) contrasting in their frost-tolerance was studied during plant cold hardening (3°C, 3 days). The sensitivity of subcellular structures to oryzalin depended closely on cell metabolic activity and the extent of development of the cortical microtubule (MT) network. Most pronounced oryzalin-induced changes were related to enhanced cell vacuolation and the appearance of some signs of apoptosis (as judged from cytoplasm fragmentation) in some cells. In the root zone examined, cell heterogeneity increased, when, along with normally functioning cells, dramatically damaged and even completely destroyed cells appeared. Simultaneously, the activity of cyanide-resistant nonphosphorylating respiration pathway was activated, especially during cold hardening. In hardened cells, single cortical microtubules appeared in both wheat cultivars; this fact indicates that new cold-resistant subpopulations of MT were resistant to depolymerizing action of oryzalin.     

The use of colchicine as an indicator of mitotic rate in broad bean root meristems

Journal of Genetics -     

间作模式下冬小麦与春玉米根系的时空分布规律

采用大口径土钻对间作种植模式下冬小麦与春玉米根系进行取样,分析了两种作物根系的空间分布及动态变化规律．结果表明：间作冬小麦根系在空间上呈幂函数递减规律,间作春玉米根系呈指数递减规律．采用多元线性回归建立间作冬小麦和春玉米根系质量密度（R）的二维空间分布函数,经验证,两种作物根系质量密度的二维分布函数均可反映作物根系的实际生长状况．     

Changes in the mitotic cycle in lateral root meristems of Vicia faba following kinetin treatment

Roots of Vicia faba were treated with H³-Thymidine (1 C/ml) for one hour, either before or after a three hour treatment with a 10^–5 M solution of kinetin. The durations of the mitotic cycle and its constituent phases were then derived from the curves recording the rhythmic entry and exit of labeled cells in prophase, both for the kinetin treated roots and the controls. The rate of DNA synthesis was also determined for the control roots and for roots exposed to H³-Thymidine immediately following treatment with kinetin. — Control values for the durations of the mitotic cycle, G1, S, G2 and mitosis were in agreement with most of the results reported in the literature. Kinetin treatment resulted in an increase in the rate of DNA synthesis, but did not affect the number of cells undergoing DNA synthesis, i.e. kinetin, or a similar compound, may be involved in the control of the rate of DNA synthesis in plant root meristems, but it does not appear to be involved in the control of the initiation of the S period of interphase. — The durations of G1 and G2 are shorter and longer respectively in the kinetin treated roots as compared with the control values. Changes in the durations of these phases of interphase, S, cycle time and the rate of cell proliferation have been discussed with respect to time after kinetin treatment and their possible relationship to carbohydrate metabolism.Research supported by an Assistant Professor Research Grant from the University of Missouri — St. Louis.     

冬小麦根系分布规律

根据在郑州进行的冬小麦根系田间实测资料,研究了根长密度和根质量密度在砂壤土中的垂直分布.结果表明:冬小麦根量主要集中在上层,根长密度、根质量密度在0～50 cm土层内分别占57.7%和66.7%,而在50～100 cm层分别占23.4%和18.7%,根长密度和根质量密度随土壤深度的变化均符合指数函数形式;综合考虑根量分布、根系吸水等因素,确定了冬小麦适宜的底墒深度为100 cm.     

Oleate desaturation in young winter wheat root tissue

[1,2-¹⁴C]Acetate was incorporated into the lipids of young wheat (Triticum aestivum L. cv Kharkov 22 MC) root tissue, but predominantly into sterols. [1-¹⁴C]Ammonium oleate was initially incorporated mainly into phosphatidylcholine (PC), and later into triglycerides (TGs). Diglycerides (DGs) contained 16% of the lipid ¹⁴C after 5 minutes and 8% after 40 minutes. The proportion of the label of each lipid group incorporated into linoleate during an 80-minute incubation increased at similar rates for each group, and was always highest in PC. Radioactivity was detected in PC-linoleate earlier than in linoleate of the other groups. During a prolonged incubation after a 15-minute pulse labeling, the percentage of the lipid ¹⁴C incorporated into PC and DGs was high at the end of the pulse but decreased later, while that in TGs increased to 64% after 4 hours. The proportion of the label of each group recovered in linoleic acid peaked in all groups after 4 hours, except for the TGs where it increased slowly throughout the experiment. Only traces of radioactivity were detected in linolenate. The data are compatible with a pathway in which oleate is incorporated into PC, is desaturated to linoleate on PC, and where the linoleate-enriched DGs are transferred from PC to TGs.     

氮素营养对小麦根冠协调生长的调控

在植物生长箱通过溶液培养方式,对不同氮素条件下不同抗旱性的小麦品种西农1043和小偃6号的幼苗根苗生长特性进行了研究,结果表明在不同氮素浓度下,氮肥用量的提高对地上部干重和叶片气体交换参数表现为增效效应,当用量增至一定程度时,地上部干重和叶片气体交换参数均呈下降趋势,只是各自的适宜用量存在差异。培养介质氮素浓度低时,有利于小麦根系干重累积,培养介质氮素浓度高时,不利于根系干重累积。西农1043和小偃6号根长分布基本相似,水分利用效率随着根冠比的增大而降低。小麦根冠比的增加并不利于叶片水分利用效率的提高,而叶片光合作用最优的根冠比为0．5左右。     

不同环境条件下小麦氮代谢关键酶活性及籽粒品质

研究了两种环境条件下3个不同蛋白含量小麦品种的氮代谢关键酶活性及籽粒品质的差异.结果表明,龙口试验点的小麦旗叶硝酸还原酶(NR)、谷胺酰氨合成酶(GS)和籽粒谷胺酰氨合成酶活性均显著高于泰安试验点,3个品种间的酶活性顺序均为：济麦20＞优麦3号＞PH971942.优质强筋小麦品种的籽粒综合品质性状在龙口试验点的表现优于泰安试验点. 灌浆期环境因素与小麦籽粒品质和酶活性存在显著的相关性,灌浆期间的较高气温、适当干旱和寡照环境有利于提高小麦籽粒品质.龙口试验点的中、强筋小麦品种和泰安试验点的中筋小麦品种蛋白质含量与旗叶NR和GS活性均达显著正相关.小麦品种用途不同,对环境条件的要求不同,适宜的环境条件提高了氮代谢关键酶的活性,利于改善小麦品质.     

Seasonal mycorrhizal colonization of winter wheat and its effect on wheat growth under dryland field conditions

 A field experiment was conducted to determine the seasonal patterns of arbuscular mycorrhiza (AM) in a dryland winter wheat (Triticum aestivum L.) system and to determine wheat growth and P uptake responses to inoculation with mycorrhizal fungus. Broadcast-incorporated treatments included (1) no inoculation with mycorrhizal fungus, with and without P fertilizer, and (2) mycorrhizal fungal inoculation at a rate of 5000 spores of Glomus intraradices (Schenck and Smith), per 30 cm in each row, with and without fertilizer P. Winter wheat was seeded within a day after treatments were imposed, and roots were sampled at five growth stages to quantify AM. Shoot samples were also taken for determination of dry matter, grain yield and yield components, and N and P uptake. No AM infection was evident during the fall months following seeding, which was characterized by low soil temperature, while during the spring, the AM increased gradually. Increases in wheat grain yields by enhanced AM were of similar magnitude to the response obtained from P fertilization. However, responses differed at intermediate growth stages. At the tillering stage, P uptake was mainly increased by P fertilization but not by fungal inoculation. At harvest, enhanced AM increased P uptake regardless of whether or not fertilizer P was added. The AM symbiosis increased with rising soil temperatures in the spring, in time to enhance late-season P accumulation and grain production. Accepted: 15 July 1998     

Cytokinin and auxin intersection in root meristems

The hormone cytokinin promotes cell differentiation in plant roots by repressing both auxin transport and responses to auxin at the boundary between the meristem and the root elongation zone.     

人工控制有限供水对冬小麦根系生长及土壤水分利用的影响

试验在中国气象局固城农业气象试验基地的大型人工控制农田水分试验场进行。在底墒充足的条件下采用3种供水处理：拔节期一次性供水75mm(I1);返青供水37．5mm和拔节期供水37．5mm(I2);返青后生长期内无水分供给(Ick)。全生育期内用电动防雨棚遮去自然降水。试验结果表明,表层土壤(0～30cm)水多根多,根系反应敏感。上层干旱促使根系向深层发育,利用下层水量较多。I1处理减少表土层(0～30cm)的根量和根长密度,促进根系下扎,较多地利用深层土壤水分,并减少无效分蘖。虽然总穗数减少,但同I2、Ick相比籽粒数和籽粒重有较大幅度增加,提高了产量和水分利用率。根系吸水效率随土层深度增加呈下降趋势,I1在30cm以下其根系吸水效率超过了I2处理,并在100～200cm土层表现最为明显。Ick除0～30cm土层外,其余土层有效底墒供水率均较低;I1和I2两处理30～100cm有效底墒供水率均在84％以上,1～2m土层内I。大于I2。Ick由于土壤水分不足并未造成千粒重的明显下降,相反,3个处理中最高;土壤水分不足导致穗数、穗粒重、籽粒重和籽粒数的显著降低,从而造成了最终产量的降低。产量水平上的水分利用效率I1比其余处理提高了将近14％,其次为Ick,最低的是I2。在灌溉效率上,I1比I2提高了将近19％;在相同灌溉量的前提下,蒸腾效率I1比I2提高约7％。I1水分利用效率高于I2和Ick处理。可以认为：配合充足底墒,前期控水,有限的一定量的水分拔节期(关键期)一次供给比在返青和拔节分别供给,更为有效科学。     

Dynamics of mitotic index of buckwheat root meristems, developing from seeds subjected to percussive wave treatment

A method of percussive wave treatment of seeds, promoting activization of physiological processes in plants, was proposed. The influence of physical treatment on cell nuclei and phytohormones was investigated. We examined dynamics of mitotic indices (MI) of the root meristems of buckwheat seedlings 48-58 h after the treatment. The seeds were treated with pressures of 11, 23, 29 MPa. The synchrony of cell divisions was estimated according to the augmentation of maximum MI versus average MI. The maximum and the average MI of control seedlings was 9.6 and 8.1%, resp. After the treatment with the pressure of 11 MPa the average MI increased by 2.6 times, and synchrony raised by 50%. After the treatment by the pressure of 23 MPa the average value of MI did not change versus the control, but the synchrony enhanced by 2.8 times. After the treatment of the pressure of 29 MPa the average MI decreased by 31%, the synchrony increased by 33%. Examination of phase indexes allowed to reveal the damage of cytotomy, transition to metaphase, and mitotic apparatus formation. The MI of root meristems of the test seedling aged 8 days topped the control by 21, 156 and 20%. So, the pressure of 11 MPa promoted MI increase in 2 days, and those of 23 and 29 MPa in 8 days. The investigation of hormone balance allowed to detect a raising level of abscisic acid. Its influence on the plant growth depends on the content of zeatin. A hypothetical model of plant reaction mechanism was proposed, based on the obtained results. A momentary pressing in the percussive wave was a stressor, promoting the accumulation of ABA and "growth rest", that changed for an active growth induced by zeatin.     

根修剪对黄土旱塬冬小麦(Triticum aestivum)根系分布、根系效率及产量形成的影响

通过田间试验研究了不同时期根修剪处理对冬小麦（Triticum aestivum）根系大小与分布、根系效率、水分利用效率及产量形成的影响。设置4个根修剪处理：越冬期小剪根（WS）、越冬期大剪根（WB）,返青期小剪根（GS）、返青期大剪根（GB）,未剪根小麦作为对照（CK）。结果表明,到花期时,各根修剪处理小麦的在0～120cm总根量均显著小于对照。与对照相比各根修剪处理主要是显著地减少了上层土壤中的根量。但WS和GS两小剪根处理和对照相比在中层土壤中有较大的根量;花后各处理小麦旗叶的气孔导度和蒸腾速率均显著大于对照。这说明根修剪处理减少了小麦表层的根量,从而削弱了表土干旱信号对作物与外界气体交换的抑制作用。花期时各根修剪小麦的净光合速率均显著高于对照,而单位面积上的根呼吸速率均显著小于对照,根修剪处理提高了小麦的根系效率,使更多的光合产物用于籽粒生产,从而提高了小麦的收获指数。根修剪还提高了小麦的水分利用效率,其中WS、WB、GS处理的水分利用效率显著高于对照。但是GB处理的水分利用效率却没有显著提高。因此,本研究进一步证明了由不同年代品种得到的推测,认为在旱地农业中,通过遗传育种或采用适当农艺措施优化根系分布,既可以减少生长前期作物对水分的过度消耗,又能够削弱花后表土过度干旱对作物生长抑制作用,同时降低根系对同化产物的消耗,对作物产量及水分利用效率的提高具有积极的作用。     

干旱灌区冬小麦根系的生长冗余

采用管栽试验通过人为去除根系的方法对甘肃河西绿洲灌区2个冬小麦品种根系的形态特征及根系与地上部分的关系进行了研究。结果表明:去除根系的冬小麦的前期生长受到一定程度的限制,与对照相比,其根冠比及其它根系指标均有所下降,且根系去除程度越大降低幅度越大;生长后期小麦根系出现了超补偿效应;成熟期,去除1/4根系和去除1/2根系处理的冬小麦无论是主茎还是分蘖的穗长、穗质量、穗粒数、粒质量等均比对照增加;但前者主茎各项指标的增幅较大,而后者分蘖的各项指标增幅较大。初步确定冬小麦在充分灌溉条件下至少有1/4的根系是冗余的。