玉米根系水流导度差异及其与解剖结构的关系

在人工气候室水培条件下,从单根水平研究了不同水分条件下玉米根系水流导度的基因型差异及解剖结构之间的关系.结果表明,抗旱性的杂交种户单四号具有水流导度上的杂种优势现象,不抗旱的父本803根系水流导度最低,3个品种根系水流导度大小为F₁代户单四号＞母本天四＞父本803;水分胁迫普遍降低了根系直径、导管直径和皮层厚度.同时,玉米品种根系的解剖结构和根系水流导度有关,正常水分条件下,根系导管直径与3个玉米品种的根系水流导度呈正相关,胁迫条件下则呈负相关.无论是在胁迫还是正常水分条件下,根系皮层厚度占根系直径的比例与根系水流导度都呈负相关,说明根系皮层是根系吸收水分的主要阻力部位.     

根径向水流导度测定技术的改进

根系径向流的水力学性质主要是根的径向水流导度,它取决于径向水流通道的状况。利用改进的现有原位的测定根系径向水流导度的蒸腾计技术,设计了一个简便的４室吸水测定装置,可一次性获得根本质部水势和根径向水流导度,缩短测定时间１０ｍｉｎ,确保测定精度。然后用改进的装置测定了生长在不同水分条件下冬小麦（Ｔｒｉｔｉｃｕｍ ａｅｓｔｉｖｕｍＬ．）根系的径向水流导度,结果显示根系的平均径向水流导度为４．６３＊１０＾     

氮磷亏缺对玉米根系水流导度的影响

在人工气候室水培条件下,从单根和整株根系两个层次研究了N、P营养与玉米(Zea mays L.)根系水流导度(root hydraulic conductivity,Lpr)间的关系。结果表明：表型抗旱的杂交种F1代户单4号和母本天四的单根水导和整株根系水导均高于不抗旱的父本478,其中天四的单根水导最高,而户单4号的整株根系水导最高。N、P亏缺均使玉米单根水导和整株根系水导降低,但与N亏块相比,P亏缺的植株具有较高的整株根系水导和较低的单根水导。整株根系的水导更能反映植物根系的输水性能。     

苗期土壤渍水对棉花恢复生长及光合生理的影响

以'中棉所41'为试验材料,采用盆栽方法,研究了苗期土壤渍水对棉花恢复生长及光合生理的影响.结果显示:(1)渍水5 d的棉苗经过10 d恢复生长,其根系活力、株高、叶面积、完全展开叶片数与对照差异不显著,但根系总长度仍比对照低11.1%(P<0.05);渍水10 d的棉苗经过10 d恢复生长,其根系活力、株高、叶面积、完全展开叶片数、根系活力均极显著低于对照.(2)渍水5 d棉苗经过10 d恢复生长,其光合速率、气孔导度、光饱和点、CO2饱和点、表观光最子效率、羧化效率以及叶绿素a、b含量与对照差异不显著;渍水10 d的棉莆经过10 d恢复生长,其光合速率、气孔导度、光饱和点、CO2饱和点、表观光量子效率、羧化效率以及叶绿素a、b含量仍显著低于对照.研究表明,棉莆经过5 d或10 d渍水胁迫后,均可以恢复生长,但随着渍水时间延长,恢复生长速度降低;在恢复生长过程中,生理活性恢复快于形态恢复;强光对于渍水后棉苗恢复生长具有明显的抑制效应.     

宁乡花猪原代和第一代血液生理生化指标比较

目的比较原代宁乡花猪与其第一代仔猪血液生理生化指标的变化。方法常规方法测定宁乡花猪F0代16头,F1代16头血液18项生理指标和13项生化指标。结果F0代与F1代部分血液生理指标如白细胞（WBC）、红细胞（RBC）、血红蛋白（HGB）、红细胞积压（HCT）等13项有显著性差异（P〈0．05）;部分血液生化指标如总胆红素（TBIL）,尿素氮（BUN）,总蛋白（TP）,白／球蛋白（ALB／GLB）,葡萄糖（GLU）,有显著性差异（P〈0．05）;其他指标均无统计学差异。结论2代宁乡花猪之间部分血液生理生化指标有显著性差异。得到的数据可以为实验动物化研究提供相应的基础生理参考数据。     

植物根系水分导度及影响因素

根系水分导度（Lpr）是表示根系吸收和运输水分能力的生理指标,文章介绍Lpr的研究进展。     

籽粒低锌与高锌含量基因型水稻锌营养特性的比较

采用溶液培养和放射性同位素技术,比较籽粒低锌含量基因型水稻（Ｏｒｙｚａ ｓａｔｉｖａ Ｌ．）湘早籼１７与籽粒高锌含量基因型水稻Ｖ５６根系形态及有关生理特性的差异,发现Ｖ５６的根系比湘早籼１７大（根较长,根体积较大,生物量较高）、根冠比值较高及根系吸收锌的Ｋｍ值较低,因而对锌的吸收量较大。这些特性可作为筛选籽粒高锌含量基因型水稻的指标。     

电子束辐射唐菖蒲球茎对M1叶片的影响初探

为了探讨电子束对唐菖蒲诱变育种的可行性和不同剂量的电子束对叶片的影响;用能量为3MeV的不同剂量电子束辐照唐菖蒲“超级”球茎,对其M1代的叶片进行了研究。 光合作用率,蒸腾速率,细胞间隙CO₂浓度和气孔导度等光合指标在低剂量时变化均不明显,随着剂量的增价,辐照对蒸腾速率和气孔导度起到明显的刺激作用并达到0.05的显著水平;通过对电子束处理后唐菖蒲叶片叶绿素含量的测定表明,叶绿素含量及叶绿素a/b比值均发生了变化,并且叶绿素a含量在240Gy处理后达到最大值,且达到了0.05的显著水平;扫描电镜观察发现,高剂量处理的M1代植株表皮毛与气孔结构均发生改变,叶表面组织特征明显排列杂乱不规则。由此表明,电子束辐照对唐菖蒲叶片的形态与生理均能产生明显的影响。     

电子束辐射唐菖蒲球茎对M1叶片的影响初探

为了探讨电子柬对唐菖蒲诱变育种的可行性和不同剂量的电子柬对叶片的影响;用能量为3MeV的不同剂量电子柬辐照唐菖蒲“超级”球茎,对其M1代的叶片进行了研究。光合作用率,蒸腾速率,细胞间隙CO2浓度和气孔导度等光合指标在低剂量时变化均不明显,随着剂量的增加,辐照对蒸腾速率和气孔导度起到明显的刺激作用并达到0．05的显著水平;通过对电子柬处理后唐菖蒲叶片叶绿素含量的测定表明,叶绿素含量及叶绿素a／b比值均发生了变化,并且叶绿素a含量在240Gy处理后达到最大值,且达到了0．05的显著水平;扫描电镜观察发现,高剂量处理的M1代植株表皮毛与气孔结构均发生改变,叶表面组织特征明显排列杂乱不规则。由此表明,电子束辐照对唐菖蒲叶片的形态与生理均能产生明显的影响。     

饲喂雌鼠大豆异黄酮对后代雌性生殖性状的影响

目的研究雌性小鼠饲喂异黄酮后对其后代雌鼠生殖性状的影响。方法分别在雌鼠从断奶到妊娠前和妊娠期间两个不同阶段的日粮中添加不同剂量的大豆异黄酮（0、50、400 mg/kg）。记录F1代的出生窝产仔数、出生窝重、雌鼠的阴道最早开张时间和最早见栓时间,以及后代雌鼠性成熟期和体成熟期生殖器官重量、血清雌激素的含量。结果雌鼠妊娠期饲喂含50、400 mg/kg大豆异黄酮的饲料后F1代的窝产仔数显著高于对照组（P〈0.05）;雌鼠妊娠期采食400 mg/kg大豆异黄酮饲料,其后代雌鼠初次配种时间明显延迟（P〈0.05）;45、65日龄体重显著低于对照组,65日龄子宫重显著低于对照组,卵巢重显著高于对照组;血清中雌激素含量显著低于对照组（P〈0.05）,妊娠期间采食50 mg/kg大豆异黄酮饲料,其F1代雌鼠仅窝产仔数和45日龄时血清中雌激素含量受到影响;而雌鼠从断奶到怀孕期间饲喂含大豆异黄酮饲料的F1代在各项指标与对照组均差异无显著性。结论雌鼠妊娠期间饲喂含400 mg/kg大豆异黄酮的饲料会显著影响其雌性后代的初情期、生殖器官发育、血清雌激素含量等生殖生理性状,而在非妊娠期饲喂含大豆异黄酮饲料对F1代无显著影响。     

压力室测定根系导水率方法探讨

用压力室连续测定了玉米根系长压和降压过程的导水率,结果表明,降压过程湍 得的根系导水率显著大于用升压过程的,并且前者的相关系数大于后者,这种差异是由于这两个过程中质外体途径细胞壁空间充水量不同造成的,开始升压时,由于细胞壁空间含水量低,质外体途径阻力大,导致非结构阻力;随着压力的升高,细胞壁空间含水量增大,质外体途径导度增大,减小甚至可以消除非结构阻力,降压法可以使根系快速复水,消除传统方法因长时间复水所致根结构的改变。建议用降压法测定根系导水率。     

Are lianas more drought-tolerant than trees? A test for the role of hydraulic architecture and other stem and leaf traits

Lianas are an important component of Neotropical forests, where evidence suggests that they are increasing in abundance and biomass. Lianas are especially abundant in seasonally dry tropical forests, and as such it has been hypothesized that they are better adapted to drought, or that they are at an advantage under the higher light conditions in these forests. However, the physiological and morphological characteristics that allow lianas to capitalize more on seasonal forest conditions compared to trees are poorly understood. Here, we evaluate how saplings of 21 tree and liana species from a seasonal tropical forest in Panama differ in cavitation resistance (P ₅₀) and maximum hydraulic conductivity (K _h), and how saplings of 24 tree and liana species differ in four photosynthetic leaf traits (e.g., maximum assimilation and stomatal conductance) and six morphological leaf and stem traits (e.g., wood density, maximum vessel length, and specific leaf area). At the sapling stage, lianas had a lower cavitation resistance than trees, implying lower drought tolerance, and they tended to have a higher potential hydraulic conductivity. In contrast to studies focusing on adult trees and lianas, we found no clear differences in morphological and photosynthetic traits between the life forms. Possibly, lianas and trees are functionally different at later ontogenetic stages, with lianas having deeper root systems than trees, or experience their main growth advantage during wet periods, when they are less vulnerable to cavitation and can achieve high conductivity. This study shows, however, that the hydraulic characteristics and functional traits that we examined do not explain differences in liana and tree distributions in seasonal forests.     

Aerenchyma Formed Under Phosphorus Deficiency Contributes to the Reduced Root Hydraulic Conductivity in Maize Roots

Root hydraulic conductivity has been shown to decrease under phosphorus （P） deficiency. This study Investigated how the formation of aerenchyma is related to this change. Root anatomy, as well as root hydraulic conductivity was studied In maize （Zea mays L.） roots under different phosphorus nutrition conditions. Plant roots under P stress showed enhanced degradation of cortical cells and the aerenchyma formation was associated with their reduced root hydraulic conductivity, supporting our hypothesis that air spaces that form in the cortex of phosphorusstressed roots Impede the radial transport of water in a root cylinder. Further evidence came from the variation In aerenchyma formation due to genotypic differences. Five maize inbred lines with different porosity in their root cortex showed a significant negative correlation with their root hydraulic conductivity. Shoot relative water content was also found lower In P-deficient maize plants than that in P-sufficient ones when such treatment was prolonged enough, suggesting a limitation of water transport due to lowered root hydraulic conductivity of P-deficient plants.     

Effect of partial root excision on transpiration, root hydraulic conductance and leaf growth in wheat seedlings.

Removal of four out of five roots did not lower transpiration and stomatal conductivity of wheat (Triticum durum Desf.) seedlings. Water content of mature expanded leaf lamina remained constant at control levels. The results suggest that the only remaining root was capable to supply the shoot with water. This was evidenced by an increase in hydraulic conductivity of the root system following partial root excision measured at low subatmospheric pressures induced by vacuum. In the absence of a hydrostatic gradient, water flow from reduced root system was initially not higher than from an intact system, but increased subsequently. ABA content was increased in roots 1 h after partial root excision, which might contribute to the increase in hydraulic conductivity.     

Hydraulic regulation strategies for whole-plant water balance of two maize inbred lines differing in drought resistance under short-term osmotic stress

The conservation of water in agriculture requires an understanding of the mechanisms of plant–water relations. This study aimed to reveal hydraulic regulation strategies of maize (Zea mays L.) for maintaining the plant water balance during drought. The water relations of two maize inbred lines (Tian4 and 478) that differ in their resistance to drought in the field were investigated under well-watered conditions and osmotic stress induced with 10 % PEG 6000. The leaf transpiration rate and leaf water potential of 478 varied diurnally, but remained constant in Tian4, which is more drought resistant. Tian4 plants showed morphological, anatomical and physiological advantages that protected them from foliar water loss. The strategies of leaf hydraulics to regulate leaf water balance during the day and during short-term osmotic stress also differed between Tian4 and 478. The leaf hydraulic conductivity of Tian4 and 478 increased temporarily, but their root hydraulic conductivities were reduced under osmotic stress. However, the root hydraulic conductivity of Tian4 subsequently recovered. Lower and rapidly reduced leaf transpiration and the ability of root hydraulics to recover from short-term osmotic stress can help explain the strategies for plant water balance of drought-tolerant maize.     

控制性分根区交替滴灌对苹果幼树形态特征与根系水分传导的影响

采用固定滴灌(根区一侧固定供水)、控制性分根区交替滴灌(根区两侧交替供水)和常规滴灌(紧贴幼树基部供水)3种灌水方式和3种灌水定额(固定滴灌和交替滴灌均为10、20和30 mm,常规滴灌为20、30和40 mm),对比研究了控制性分根区交替滴灌对苹果幼树形态特征与根系水分传导的影响.结果表明： 交替滴灌的根区两侧土壤出现反复干湿交替过程,常规滴灌的根区两侧土壤含水率差异不显著.在灌水定额相同时,灌水侧的土壤含水率在3种灌水方式间差异不显著.与常规滴灌和固定滴灌相比,交替滴灌显著增加了苹果幼树的根冠比、壮苗指数和根系水分传导,在30 mm灌水定额处理下,交替滴灌的根冠比分别增加31.6%和47.1%,壮苗指数增加34.2%和53.6%,根系水分传导增加9.0%和11.0%.3种灌水方式下,根干质量和叶面积均与根系水分传导呈显著线性正相关.控制性分根区交替滴灌增强了苹果幼树根系水分传导的补偿效应,促进了根系对水分的吸收利用,有利于干物质向各个器官均衡分配,显著提高了根冠比和壮苗指数.     

Gating of aquaporins by low temperature in roots of chilling-sensitive cucumber and chilling-tolerant figleaf gourd

Effects of low temperature (8 degrees C) on the hydraulic conductivity of young roots of a chilling-sensitive (cucumber, Cucumis sativus L.) and a chilling-resistant (figleaf gourd, Cucurbita ficifolia Bouche) crop have been measured at the levels of whole root systems (root hydraulic conductivity, Lp(r)) and of individual cortical cells (cell hydraulic conductivity, Lp). Exposure of roots to low temperature (LRT) for up to 6 d caused a stronger suberization of the endodermis in cucumber compared with figleaf gourd, but no development of exodermal Casparian bands in either species. Changes in anatomy after 6 d of LRT treatment corresponded with a reduction in hydrostatic root Lp(r) of cucumber roots by a factor of 24, and by a factor of 2 in figleaf gourd. In figleaf gourd, there was a reduction only in hydrostatic Lp(r) but not in osmotic Lp(r) suggesting that the activity of water channels was not much affected by LRT treatment in this species. Changes in cell Lp in response to chilling and recovery were similar to the root levels, although they were more intense at the root level. Activation energies (E(a)) and Q10 of water flow as measured at the cell level were high in cucumber (E(a)=109+/-13 kJ mol(-1); Q(10)=4.8+/-0.7; n=6-10 cells), but small in figleaf gourd (E(a)=11+/-2 kJ mol(-1); Q10=1.2+/-0.1; n=6-10 cells). Roots of figleaf gourd recovered better from LRT treatment than those of cucumber. In figleaf gourd, recovery (at both the root and cell level) often resulted in Lp and Lp(r) values which were even bigger than the original, i.e. there was an overshoot in hydraulic conductivity. These effects were larger for osmotic (representing the cell-to-cell passage of water) than for hydrostatic Lp(r). After a short-term (1 d) exposure to 8 degrees C followed by 1 d at 20 degrees C, hydrostatic Lp(r) of cucumber nearly recovered and that of figleaf gourd still remained higher due to the overshoot. By contrast, osmotic Lp(r) and cell Lp in both species remained high by a factor of 3 compared with the control, possibly due to an increased activity of water channels. After preconditioning of roots at LRT, increased hydraulic conductivity was completely inhibited by HgCl2 at both the root and cell levels. Different from figleaf gourd, recovery from chilling was not complete in cucumber after longer exposure to LRT. It is concluded that at LRT, both changes in the activity of aquaporins (AQPs) and alterations of root anatomy determine the water uptake in both species. The high temperature dependence of cell Lp in cucumber suggests conformational changes of AQPs during LRT treatment which result in channel closure and in a strong gating of AQP activity by low temperature. This mechanism is thought to be different from that in figleaf gourd where AQPs reacted in the conventional way, i.e. low temperature affected the mobility of water molecules in AQPs rather than their open/closed state, and Q(10) was low.     

The integration of whole-root and cellular hydraulic conductivities in cereal roots

The hydraulic conductivities of excised whole root systems of wheat (Triticum aestivum L. cv. Atou) and of single excised roots of wheat and maize (Zea mays L. cv. Passat) were measured using an osmotically induced back-flow technique. Ninety minutes after excision the values for single excised roots ranged from 1.6·10^-8 to 5.5·10^-8 m·s^-1·MPa^-1 in wheat and from 0.9·10^-8 to 4.8·10^-8 m·s^-1·MPa^-1 in maize. The main source of variation was a decrease in the value as root length increased. The hydraulic conductivities of whole root systems, but not of single excised roots, were smaller 15 h after excision. This was not caused by occlusion of the xylem at the cut end of the coleoptile. The hydraulic conductivities of epidermal, cortical and endodermal cells were measured using a pressure probe. Epidermal and cortical cells of both wheat and maize roots gave mean values of 1.2·10^-7 m·s^-1·MPa^-1 but in endodermal cells (measured only in wheat) the mean value was 0.5·10^-7 m·s^-1·MPa^-1. The cellular hydraulic conductivities were used to calculate the root hydraulic conductivities expected if water flow across the root was via transcellular (vacuole-to-vacuole), apoplasmic or symplasmic pathways. The results indicate that, in freshly excised roots, the bulk of water flow is unlikely to be via the transcellular pathway. This is in contrast to our previous conclusion (H. Jones, A.D. Tomos, R.A. Leigh and R.G. Wyn Jones 1983, Planta 158, 230–236) which was based on results obtained with whole root systems of wheat measured 14–15 h after excision and which probably gave artefactually low values for root hydraulic conductivity. It is now concluded that, near the root tip, water flow could be through a symplasmic pathway in which the only substantial resistances to water flow are provided by the outer epidermal and the inner endodermal plasma membranes. Further from the tip, the measured hydraulic conductivities of the roots are consistent with flow either through the symplasmic or apoplasmic pathways.Symbols L _{p, cell} cell hydraulic conductivity - L _{p, root} root hydraulic conductivity - L _{p, root} calculated root hydraulic conductivity - root reflection coefficient     

Circadian rhythm of root pressure in popular and its driving factors

Aims Our main purposes were to investigate root pressure and its circadian rhythm of excised roots in ‘84K’ popular (Populus alba × P. glandulosa) cultured in soil and solution, to explore the influencing factors and their relationships with root pressure systematically and to understand the generation and rhythm regulation of root pressure. Methods We investigated the root pressure of excised roots in ‘84K’ popular using the method of digital pressure transducer. The diurnal rhythm of excised roots was conducted through different experimental treatments including sampling in different time, defoliation and girdling, together with ambient condition like soil temperature, differential or consistant temperature during day and night. Then we discussed the effects of root respiration and hydraulic conductivity on root pressure by further using chemical inhibitor. Furthermore, diurnal variation of osmotic potential and ions content as well as soluble sugar content of exudation was determined in order to explore their relationships with root pressure rhythm. Important findings Root pressure of excised roots in popular had diurnal rhythm which was higher during daytime and lower overnight. It reached its peak value in the morning to noon and valley value at 20:00. Root pressure of excised roots sampled at different time and cultured in different medium had influence on the rhythm of root pressure to some degrees, but did not the general rhythm of high in daytime and low overnight. Defoliation, girdling and the inhibitors for root respiration or cytomembrane hydraulic conductivity could affect the maximum value of root pressure while have no significant influence on the daily rhythm. Defoliation, girdling and respiration inhibitor reduced the maximum value of root pressure, whereas the hydraulic conductivity inhibitor had little influence on root pressure. The maximum value of root pressure declined with the decrease in soil temperature which could change the rhythm of root pressure. The synchronous change in the maximum value of root pressure and root respiration rate with temperature indicated that root respiration contributed to the change of root pressure along with temperature. Osmotic potential of root exudation was higher during the daytime and lower at night. Diurnal variations of ions and soluble sugar content of exudation were consistant with that of osmotic potential. The peak of root pressure measured under the condition of differential temperature during day and night was significant higher than that measured under constant temperature. In conclusion, root pressure of the poplar ‘84K’ showed significant diurnal rhythm, i.e. higher during the daytime and lower at night. The maximum value of root pressure was mainly regulated by root respiration metabolism. The factors such as respiration inhibitor, respiration substrate and temperature influence the value of the maximum root pressure of poplar ‘84K’. Root hydraulic conductivity had no significant influence on root pressure.