高Fe2+ 对水稻离体根边缘细胞的影响

以水稻"汕优10号"为试验材料,悬空气培法获得根边缘细胞,研究水稻边缘细胞的数量、活性和脱离根冠后对高Fe2 的响应过程.结果显示,水稻根长为1 mm时,就形成了205个边缘细胞,随着根的伸长数目不断增加,根长25 mm时,边缘细胞数目最大;根长20 mm时边缘细胞活性最大;根长2 mm时,根冠果胶甲基酯酶(Pectin methyl esterase, PME)活性最高,水稻边缘细胞的形成与根冠PME活性相关.高Fe2 对离体边缘细胞有毒害效应,用浓度为200 μmol·L-1的Fe2 溶液处理48 h后,细胞活性比对照下降了72.70%, 但用400 μmol·L-1 Fe2 溶液处理时,细胞活性有所回升,这可能是边缘细胞耐铁毒的一种应激性反应;根冠PME活性随着Fe2 浓度的增加先上升后下降,表明根冠PME活性与植物铁毒有关.     

外源钾对铁胁迫下水稻细胞壁多糖含量及耐铁性的影响

以耐铁毒型水稻品种协优9308和铁毒敏感型水稻品种Ⅱ优838为实验材料,采用溶液培养法研究250mg.L-1Fe2+(EDTA-Fe2+)胁迫下,不同钾水平对两种水稻的生长特性、酸性磷酸酶(APA)、果胶甲酯酶(PME)、根系果胶含量、半纤维素1含量以及半纤维素2含量的影响。结果表明,经250mg.L-1Fe2+处理7d和14d后,协优9308和Ⅱ优838的相对根长明显下降,APA、PME的活性显著升高,果胶含量、半纤维素1含量、半纤维素2含量显著增加,Ⅱ优838酶活性及细胞壁多糖含量提高幅度较大,表现出其铁毒敏感性,并且随着处理时间的延长,铁胁迫对两种水稻相对根长,PME活性,HC1含量及HC2含量的影响越显著,但APA活性和果胶含量则没有明显变化。加入外源钾可以不同程度的降低酶活性及细胞壁多糖含量,外源钾浓度为200mg.L-1,对水稻相对根长,APA活性,HC1含量缓解效果较好;外源钾浓度为400mg.L-1,对PME活性,果胶含量缓解效果较好。随着外源钾浓度升高,水稻铁毒症状得到不同程度的缓解,但钾浓度高于200mg.L-1又会对水稻造成新的胁迫。由此推测,水稻通过提高根系细胞壁多糖含量来增加根尖铁的结合位点,以及细胞壁的厚度和刚性,并降低细胞壁的伸展性,使根细胞的伸长受抑,从而提高其铁耐性。     

麻疯树根边缘细胞生物学特性及镉对其活性的影响

以麻疯树为试材,采用悬空气法,探讨麻疯树离体根边缘细胞的生物学特性及重金属镉(Cd2+)对根边缘细胞活性的影响.结果表明,麻疯树根边缘细胞大多数呈椭圆型,少数成弯曲的长条型;根长为15 mm时,边缘细胞的生物学活性(存活率)最大;根冠果胶甲基脂酶(PME)酶活性随着根的伸长有所降低.镉对麻疯树根边缘细胞产生明显毒害,随着镉浓度和处理时间的增加,边缘细胞的活性都呈现下降的趋势.     

绿豆根边缘细胞发育特性

以东北绿豆为试验材料,采用琼脂悬空培养法,研究了绿豆边缘细胞的发育特性。结果表明:绿豆根尖发育初期根边缘细胞呈球形,随着根尖伸长逐渐发育形成椭圆形、长椭圆形和长条形;发育过程中,根边缘细胞具有较高的存活率,在根长大于10mm后根边缘细胞的存活率均在70%～80%之间并趋于稳定;在根长为25～30mm时根边缘细胞数目达到最大值(约13 000个);根冠果胶甲基酯酶(PME)活性在根长5mm时达到最高值(1.486H+μmol.root cap-1.h-1),此后随着根的伸长,根冠PME活性在1.107～1.256H+μmol.root cap-1.h-1间变化并趋于稳定。     

番茄根边缘细胞生物学特性及铝对其活性的影响

以番茄为试材,采用悬空气法,探讨番茄根边缘细胞的生物学特性及铝对其活性的影响。结果表明,第1个番茄边缘细胞几乎与初生根同时出现,当根长到10 mm时,番茄边缘细胞达最大值(893个)。边缘细胞的活性(成活率)一直维持在93%以上。PME活性随着根的伸长有所降低。铝对番茄边缘细胞产生明显毒害,随着铝浓度和处理时间的增加,边缘细胞的活性显著降低。     

真盐生植物盐地碱蓬根系边缘细胞在耐盐中的作用初探

以黄河三角洲潮间带盐地碱蓬种子生成的幼苗为材料,研究了NaCl胁迫对盐地碱蓬生长与根系边缘细胞的影响。盐地碱蓬的第一个边缘细胞几乎与根尖同步产生,当根长达到13mm时,边缘细胞数目达到最大值。NaCl胁迫抑制边缘细胞的活性,但低浓度的NaCl处理增加边缘细胞的数目。低浓度NaCl处理时果胶甲基酯酶（PME）的活性比对照有明显增加,超氧化物歧化酶（SOD）活性随着NaCl浓度的增加呈现先上升后下降的趋势,低浓度NaCl可以增加盐地碱蓬根内过氧化氢酶（CAT）的活性,NaCl处理时间和处理浓度都对过氧化物酶（POD）活性的影响不明显。这些结果表明,盐地碱蓬至少部分通过增加调控活性氧（ROS）水平增加PME活性及根系边缘细胞数目来抵抗NaCl胁迫。     

大豆（Glycine max L.）边缘细胞对铝毒的生理生态响应

以大豆浙春2号(铝耐性)和华春18号(铝敏感)为材料,研究了铝胁迫下附着于根尖边缘细胞(即原位边缘细胞)的存活率、根伸长抑制率和PME活性变化以及Al3 对离体后边缘细胞存活率、黏液层厚度的影响。结果表明:铝胁迫下附着于根尖的边缘细胞比离体边缘细胞有更高的活性,前者Al3 处理24h后,其成活率仍能达到74%以上,而后者Al3 处理12h,浙春2号和华春18号边缘细胞的活性在400μmol/L时分别只有44.58%和26.16%;前后两者细胞活性都有随着Al3 浓度升高和处理时间的延长,边缘细胞活性呈越来越低的变化趋势,而离体边缘细胞Al3 处理6h时,相对于敏感性品种而言,高浓度Al3 (≥200μmol/L)有利于铝耐性品种的边缘细胞存活。随Al3 浓度的提升,果胶甲基酯酶(PME)活性增加,根伸长受抑加剧,敏感品种PME活性及铝造成的根伸长抑制均高于耐性品种;同时,Al3 对黏液的产生有一定的影响,黏液层的厚度随Al3 浓度成正向变化趋势。不同Al3 浓度及处理时间下,耐性品种都比敏感品种边缘细胞有较高的活性、分泌较多的黏液。以上结果说明Al3 对边缘细胞具有一定的毒害效应,果胶甲基酯化程度、根伸长受抑及边缘细胞黏液的分泌是根冠对Al毒胁迫反应的结果。     

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。     

NaCl胁迫对黄瓜根系边缘细胞发生的影响

以黄瓜为试材,研究了NaCl处理对植株生物量、根长、根系活力、根边缘细胞的数目和活性及黏胶层厚度的影响。结果表明,NaCl处理降低了植株生物量与根系长度,增加了黄瓜幼苗的根系活力。黄瓜边缘细胞的出现几乎与根同时发生,当根长达到25mm时,边缘细胞的数目与活性均达到最大值。NaCl处理对边缘细胞的数目与活性表现出一定的抑制作用。离体根尖的边缘细胞活性也随NaCl处理浓度与处理时间的增加而逐渐减小,但根边缘细胞黏胶层厚度却随NaCl处理浓度的增加而增加。总之,NaCl对黄瓜幼苗造成一定伤害,但根系边缘细胞可通过降解死亡与增加黏胶的分泌量在一定程度上减轻这种伤害程度。     

大麦根边缘细胞发育的生物学特性

FDA—PI(fluorescein diacetate-propidium iodide)检测结果表明,在大麦种子萌发过程中,根边缘细胞(border cells)活性约为95％。0．5mol/L甘露醇有利于离体边缘细胞的生存。第一个边缘细胞几乎与初生根根尖同步出现,当根长为20—25mm时,边缘细胞数目达到最大值(约1400);移去全部边缘细胞48h后,又有新的边缘细胞形成。与25℃相比,15和35℃明显抑制根的伸长,但不明显抑制边缘细胞的发育。在边缘细胞诱导和发育过程中,边缘细胞的游离与根冠果胶甲基酯酶活性有密切的正相关性。     

Effect of toxic Fe2+ levels on the biological characteristics of rice root border cells

Root border cells are a population of rhizosphere cells surrounding the root tips but separated from them. The root tip is a major target of Fe²⁺ toxicity; thus, it was hypothesized that the border cells might protect or exacerbate Fe²⁺ toxicity. To explore the effects of excess Fe²⁺ on the border cells in rice (Oryza sativa L.), experiments were carried out using the border cells in vitro (Shanyou No. 10). The border cells were precultured under ??hanging in the air?? and detached from the root tips. The shape, numbers, and viability of border cells were examined during exposure to toxic levels of Fe²⁺. When the root was 1 mm long, there were 205 border cells on average. With the growth of the root, more border cells were observed. When the root grew to 25 mm long, the total number of border cells reached a maximum, while the maximum activity of border cells appeared when the root was 20 mm long. The pectin methyl esterase (PME) activity of the root cap peaked at a root length of 2 mm. Border cell development was related to PME activity in rice. Excessive Fe²⁺ was toxic to detached border cells. After treatment with 200 ??M Fe²⁺ solution for 48 h, cell viability decreased by 72.70%. However, when treated with 400 ??M Fe²⁺ solution, the number of viable cells was actually higher, suggesting the induction of a cellular self-protection response. The activity of PME first increased under high concentrations of Fe²⁺ and then decreased. These results indicate that toxic levels of Fe²⁺ modulate PME activity and border cell survival.     

Effect of iron plaque outside roots on nutrient uptake by rice (Oryza sativa L.). Zinc uptake by Fe-deficient rice

This solution culture study examined the effect of the deposition of iron plaque on zinc uptake by Fe-deficient rice plants. Different amounts of iron plaque were induced by adding Fe(OH)₃ at 0, 10, 20, 30, and 50 mg Fe/L in the nutrient solution. After 24 h of growth, the amount of iron plaque was correlated positively with the Fe(OH)₃ addition to the nutrient solution. Increasing iron plaque up to 12.1 g/kg root dry weight increased zinc concentration in shoots by 42% compared to that at 0.16 g/kg root dry weight. Increasing the amount of iron plaque further decreased zinc concentration. When the amounts of iron plaque reached 24.9 g/kg root dry weight, zinc concentration in shoots was lower than that in shoots without iron plaque, implying that the plaque became a barrier for zinc uptake. While rice plants were pre-cultured in –Fe and +Fe nutrient solution in order to produce the Fe-deficient and Fe-sufficient plants and then Fe(OH)₃ was added at 20, 30, and 50 mg Fe/L in nutrient solution, zinc concentrations in shoots of Fe-deficient plants were 54, 48, and 43 mg/kg, respectively, in contrast to 32, 35, and 40 mg/kg zinc in shoots of Fe-sufficient rice plants. Furthermore, Fe(OH)₃ addition at 20 mg Fe/L and increasing zinc concentration from 0.065 to 0.65 mg Zn/L in nutrient solution increased zinc uptake more in Fe-deficient plants than in Fe-sufficient plant. The results suggested that root exudates of Fe-deficient plants, especially phytosiderophores, could enhance zinc uptake by rice plants with iron plaque up to a particular amount of Fe.     

反枝苋水浸提液与挥发油对黄瓜根尖的影响

采用悬空气法研究了在入侵植物反枝苋(Amaranthus retroflexus L.)水浸提液和挥发油作用下,黄瓜根缘细胞活性、根冠果胶甲基酯酶(PME)、根尖过氧化氢酶(CAT)、过氧化物酶(POD)、超氧化物歧化酶(SOD)以及丙二醛(MDA)含量的变化规律.结果表明:反枝苋水浸提液对黄瓜根的生长无显著性影响而挥发油显著抑制黄瓜根的生长,且随浓度增大抑制作用显著增强.PME活性随着水浸提液浓度的增大呈先上升后下降趋势,而随着挥发油浓度的升高呈现逐渐上升的趋势;水浸提液和挥发油均降低了对根缘细胞的存活率,这种抑制作用随浓度的增加而增大;随着处理液浓度增大,黄瓜根尖中MDA含量、CAT活性整体表现为增加,SOD活性先升高后降低,POD活性与对照差异不显著.反枝苋挥发油的化感效应大于水浸提液的化感效应.     

Characteristics of Root Plasma Membrane ATPase and H+- extrusion in a K+- deficit Tolerant Rice Variety

The characteristics of root plasma membrane ATPase (PM-ATPase) of "Weiyou 49", a K+ -deficit tolerant rice (Oryza sativa L. ) variety and of "Yuanyou 1", a K+ -deficit non-tolerant rice variety, had some similarities:Their optimum pH value were both about 6.0; Their activities reached the maximum at ATP concentration of 3 mmol/L; Km was 0.85 mmol/L and external K+ stimulated their activities. However, when [K+ ] was less than or equal to 50 mmol/L in the medium, the increasing of K + stimulated the activity of the PM-ATPase of "Weiyou 49" much more than that of "Yuanyou 1". When [K+ ] was between 100 to 200 mmol/L, the difference of the PM-AT- Pase activities decreased between the two rice varieties caused by K + stimulation. The basic H + extrusion of the two varieties had no apparent difference, but the H + extrusion stimulated by K + was different. The H+ extrusion of "Weiyou 49" was relatively more sensitive to external K+ . The experiment using inhibitors showed that there were close relationship between the PM-ATPase activi- ties stimulated by K+ and K+ uptake in the two varieties. The inhibition of PM-ATPase activity and H+ -extrusion stimulated by K+ reduced the K+ uptake of the root segments in both varieties. So the possible reason for "Weiyou 49" growing well in the low external K+ was that its PM-ATPase and H+ extrusion was more sensitive to external K+ , especially when [K+ ] was low.     

Effects of Al<Superscript>3+</Superscript> on the biological characteristics of cowpea root border cells

Root border cells (RBC) are cells surrounding the root apex. They are functionally different from the apex and are considered to play a role in the protection of the root tip from biotic and abiotic stresses. We investigated RBC viability, formation, and pectin methylesterase (PME) activity of the root caps during RBC development in cowpea (Vigna ungniculata ssp. sesquipedalis) under aeroponic culture. The results showed that the border cells formed almost synchronously with the emergence of the root tip. The number of border cells reached the maximum when roots were approximately 15 mm long. Pectin methylesterase (PME) activity of the root cap peaked at a root length of 1 mm. Root border cells separated from the root cap died within 24 h under Al³⁺ stress while those still attached to the root cap maintained 85% viability at 48 h after treatment. The PME activity did not differ significantly under different Al³⁺ treatments.     

Characterization of tissue tolerance to iron by molecular markers in different lines of rice

Ferrous iron (Fe2+) toxicity is a major disorder in rice prod uction on acid, flooded soils. Rice ( Oryza sativa L.) genotypes differ widely in tolerance to Fe2+ toxicity, which makes it possible to bre ed more tolerant rice varieties. Tissue tolerance to higher iron concentrations in plants has been considered to be important to Fe2+ tolerance in ri ce. Segregation for leaf bronzing and growth reduction due to Fe2+ to xicity was observed in a doubled haploid (DH) population with 135 lines derived from a Fe2+ tolerant japonica variety, Azucena, and a sensitive indic a variety, IR64 in a solution culture with Fe2+ stress condition at a Fe2+concentration of 250 mg L-1 at pH 4.5. To better understand the mechanism of tissue tolerance, Leaf Bronzing Index (LBI), total iron concentration in shoot tissue and the enzymes of ascorbate peroxidase (AP), dehydroascorbate reductase (DR) and glutathione reductase (GR), and concentrations of ascorbate (AS) and dehydroascorbate (DHA), which are involved in the ascorbate-specific H2O2-scavenging system, were determined for the population under Fe2+ stress. A non-normal distribution of LBI was found. About 38 lines showed no bronzing, while the lines with non-zero LBI values ranged from 0.05 to 0.85 and showed a normal distribution. The other parameters measured showed normal distribution. The total iron concentrations in the 38 tolerant lines ranged from 1.76 mg Fe g-1 to 4.12 mg Fe g-1 and was in a similar range as in the non-tolerant genotype (2.04 – 4.55 mg Fe g-1). No significant differences in the activities of the enzymes were found between the parents under normal culture, but remarkably higher Fe2+ induced enzyme activities were observed in the tolerant parent. AS was similar between the parents under both normal and Fe2+ stress, but its concentration was sharply decreased under Fe2+ stress. DHA was much lower in the tolerant parent than in the sensitive parent under Fe2+ stress. Single locus analysis and interval mapping analysis based on 175 molecular markers revealed that the interval flanked by RG345 and RZ19 on chromosome one was an important location of gene(s) for Fe2+ tolerance. The ascorbate-specific system for scavenging Fe2+-mediated oxygen free radicals may be an important mechanism for tissue Fe2+ tolerance. A gene locus with relative small effect on root ability to exclude Fe2+ was also detected.     

水稻根表铁膜吸附镉及植株吸收镉的动态

采用营养液培养法研究了Cd处理时间对有铁膜和无铁膜水稻根表吸附Cd及植株吸收Cd动态变化的影响.水稻根表铁膜由50 mg·L^-1 Fe^2＋（Fe₅₀）诱导形成.供试植株在含10 μmol·L^-1Cd的营养液中生长不同时间后收获.结果表明, 随Cd处理时间的延长,无铁膜和有铁膜处理水稻根表DCB-Cd含量均为先增加后减少,Cd处理2 h达到最高,之后逐渐下降并趋于稳定. 根系和地上部Cd含量均持续上升,Cd处理8 h前增加缓慢,8 h后增加幅度加大.有铁膜水稻根系和地上部Cd含量增加幅度均低于无铁膜水稻.有铁膜处理DCB-Cd含量、根系和地上部Cd含量均低于无铁膜处理.表明铁膜不影响水稻各部分Cd含量随时间的变化趋势;不同Fe处理之间根系和地上部Cd含量的差异可能与根系含Fe量有关.     

根表铁锰氧化物胶膜对不同品种水稻吸镉的影响

采用土培方法,研究了不同品种水稻吸镉的差异及其与根表铁锰氧化物胶膜的关系,结果表明：不同品种水稻其根膜,根部及地上部含镉量均存在显著性差异,且镉在不同水稻植株体内运输转移能力不同,不同水稻其根表淀积的铁锰氧化物数量也存在显著性差异,根膜及地上部的含镉量与极膜的含铁量均未达到显著性相关,但与根膜的含锰量相关性显著。