Pollen-pistil interactions in Populus: β-galactosidase activity associated with pollen-tube growth in the crosses P. nigra x P. nigra and P. nigra x P. alba

Summary In order to understand the nature of interspecific barriers in Populus, we have explored pollen/pistil interactions in intra- and interspecific crosses Populus nigra x P. nigra and P. nigra x P. alba. The kinetics of pollen-tube growth demonstrated that P. nigra and P. alba pollen tubes have distinct behavioral patterns inside P. nigra pistils. P. alba pollen tubes exhibit an unique S-shaped growth curve and an arrested growth site near the sylodium. P. nigra pollen tubes exhibit two growth phases, in the stigmatic tissues and in the ovarian cavity respectively. P. nigra and P. alba curves diverge 5 h after controlled pollination and could be related to a change in the physiology of the P. nigra pollen tube, which shifts from an autotrophic to a heterotrophic type of nutrition. Protein analysis of pollinated stigmatic extracts (0,6 and 20 h after pollination) revealed qualitative and quantitative differences that are related to the presence of either P. nigra or P. alba pollen tubes inside the stigmatic tissues. Increasing numbers of protein bands were detectable from 0 to 20 h after pollination only in intraspecific cross. Glycoproteins were detected, and the differences observed were dependent of the cross. -Galactosidase activity was found in pollinated stigmas, but an increase in its activity (one isozyme of pHi 4.2) between 6 h and 20 h after pollination was detected only in the intraspecific cross. This enzyme could play a role in heterotrophic pollen-tube nitrition, and its activity could be the final result of a series of interactions started by the initial pollen-stigma dialog.     

Photosynthetic apparatus of chilling-sensitive plants IX. The involvement of α-tocopherol in the electron transport chain and the anti-oxidizing system in chloroplasts of tomato leaves

1. The role of tocopherols in tomato chloroplasts from fresh, cold and dark-stored as well as stored and illuminated leaves was studied.2. The cold and dark storage of leaves results in a loss of chloroplast α- and γ-tocopherols of about 30–40% accompanied by an increase in chloroplast δ-tocopherol of about 40%. On illumination of stored leaves, an elevation of α- and γ-tocopherol level to about 110 and 95% of the control, respectively, occurs, whilst δ-tocopherol content is not affected.3. Experiments performed with 2,2-diphenyl-1-picrylhydrazyl-treated chloroplasts show that only about 70% of total α-tocopherol is functionally active in the electron transport of Photosystem II between the diphenyl-carbazide (DPC) donation site and the inhibition site of DBMIB.4. A small amount of α-tocopherol quinone (about 10% of α-tocopherol content) is found in chloroplasts from fresh, fresh and illuminated as well as cold and dark-stored tomato leaves, whereas the illumination of the latter increases the chloroplast α-tocopherol quinone content 3-fold. Moreover, following the illumination of chloroplasts from cold and dark-stored as well as stored and illuminated leaves, the oxidation of exogenous α-tocopherol to α-tocopherol quinone is 2-fold faster then in chloroplasts from fresh leaves.5. The primary product (‘α-tocopheroxide’) formed during the α-tocopherol oxidation by illuminated chloroplasts was identified as 8a-hydroxy-α-tocopheron.6. Exogenous α-tocopherol inhibits the lipid photoperoxidation by about 40–50% in chloroplasts from all three kinds of tomato leaf.7. The results seem to suggest that chloroplast α-tocopherol is involved in both electron transport of PS II and antioxidizing system of chloroplasts.     

Differences in the distribution of β-glucuronidase activity demonstrated with the Fishman-Baker method in the adrenal cortex of albino rats treated with corticosteroids and after hypophysectomy

Summary Histohemical estimation of -glucuronidase was performed in the adrenals of normal rats, rats treated with corticosteroids and hypophysectomized rats. In these experiments the method described by Fishman and Baker was used. A difference was found between normal rats and rats treated with hydrocortisone and corticosterone on the one hand and hypophysectomized animals on the other. In the first group a positive reaction was found in the zona intermedia, the zona fasciculata, and the zona reticularis. In the second group a positive reaction was found in the male animals exclusively in the zona intermedia and in the female animals in both the zona intermedia and the zona glomerulosa. Although the distribution of the blue precipitate in the adrenal cortex of untreated rats is similar to the distribution of -glucuronidase as determined histo-biochemically by Nayyar and Glick we doubt, in spite of the observed difference, that the Fishman-Baker method is specific for -glucuronidase. Replacement of the specific substance 8-hydroxyquinoline glucuronide by 8-hydroxyquinoline did not affect the results.     

Relationship between the changes in the concentration of endoxan and the activity of kininforming enzymes within the Guérin tumor in rat.

The activity of rat kininforming system and endoxan level in certain organs and in the neoplastic tissue was studied. It was found that trypsin increases markedly the kininforming activity and endoxan level in the Guérin tumor, and slightly in the liver. A direct correlation between the level of endoxan when given with trypsin and the kinin activity were observed. The authors suppose that the selective accumulation of endoxan in the tumor depends on the trypsin -- induced activation of kininforming system within the neoplastic tissue.     

Ontogenesis of the α-MSH, β-MSH and ACTH cells in the foetal hypophysis of the rat. Correlation with the growth of the adrenals and adrenocortical activity

Pituitary sections from 15 to 21 day-old rat foetuses have been studied with the immunofluorescence technique, using antibodies anti alpha-MSH, anti beta-MSH and anti beta (1-24) ACTH. The first ACTH cells appear on day 17 of pregnancy in the pars distalis of the hypophysis and only on day 18 in the pars intermedia. beta-msh cells have been observed on day 16 in the pars anterior and on day 17 in the pars intermedia, while alpha-MSH cells appear only on day 18 and exclusively in the pars intermedia. The cytodifferentiation of the beta-MSH and ACTH cells occurs in the pars intermedia with about a 24 hours delay in comparison to that of the pars distalis. The first revealed cells are always located in the posterior half of the pituitary gland. The corticostimulating activity of the hypophysis has been tested with the fluorescence intensity of the corticotrophs, the adrenal weight, the adrenal content in corticosterone and the plasma corticosterone level. The fluorescence of the corticotrophs increases on day 18, shows a maximum on day 19 and decreases until term. The adrenal weight rises regularly between day 16 to day 20, thereafer the increase subsides. Adrenal and plasma corticosterone concentrations reach a peak on day 19 of pregnancy. These data suggest that hypophyseal corticostimulating activity is very high between days 18 and 19 and decreases between days 19 and 21.     

Photosynthetic responses of sun- and shade-grown barley leaves to high light: is the lower PSII connectivity in shade leaves associated with protection against excess of light?

In this study, we have compared photosynthetic performance of barley leaves (Hordeum vulgare L.) grown under sun and shade light regimes during their entire growth period, under field conditions. Analyses were based on measurements of both slow and fast chlorophyll (Chl) a fluorescence kinetics, gas exchange, pigment composition; and of light incident on leaves during their growth. Both the shade and the sun barley leaves had similar Chl a/b and Chl/carotenoid ratios. The fluorescence induction analyses uncovered major functional differences between the sun and the shade leaves: lower connectivity among Photosystem II (PSII), decreased number of electron carriers, and limitations in electron transport between PSII and PSI in the shade leaves; but only low differences in the size of PSII antenna. We discuss the possible protective role of low connectivity between PSII units in shade leaves in keeping the excitation pressure at a lower, physiologically more acceptable level under high light conditions.     

The effect of O2 and CO2 concentration on photosynthesis and glycolate accumulation in bean leaves treated with α-hydroxy-2-pyridinemethanesulfonic acid (α-HPMS), the glycolate oxidase inhibitor

¹⁴CO₂ assimilation, ¹⁴C incorporation into glycolate and glycolate accumulation in -HPMS treated bean leaves at various O₂ and CO₂ concentrations were studied. In 1% CO₂ oxygen concentration had no significant effect on glycolate accumulation and ¹⁴C incorporation into glycolate. In the CO₂ concentration range of 0.03% to 0.01%, increased oxygen concentration decreased not only ¹⁴CO₂ assimilation but also glycolate accumulation and ¹⁴C incorporation into glycolate. In 1% and 0.1% CO₂, no matter what O₂ concentration was supplied, and in 0.03% CO₂ with 2% and 21% O₂, all of the glycolate accumulated was formed from newly assimilated carbon. In 0.01% CO₂ and 2%, 21% and 100% O₂, and in 0.03% CO₂ with 100% O₂, a substantial portion of the glycolic acid that accumulated in leaves originated from endogenous unlabelled substrates. These findings are discussed in terms of possible changes in the ratio of RuBP carboxylation to RuBP oxygenation and of changes of RuBP pool size, induced by changing O₂ and CO₂ concentrations.This work was supported by the Polish Academy of Sciences, Contract No. 10.2.10.     

Is the ABA concentration in the sap collected by pressurizing leaves relevant for analysing drought effects on stomata? Evidence from ABA-fed leaves of transgenic plants with modified capacities to synthesize ABA.

Most studies on the role of ABA in the stomatal response of the whole plant to drought rely on a good estimate of ABA concentration in xylem sap. In this report, varying volumes of sap (V(sap)) were collected by pressurizing leaves cut from several lines of N. plumbaginifolia with modified capacities to synthesize ABA. Leaves were fed with solutions of known ABA concentration ([ABA](solution) from 0-500 micromol m(-3)) for 2-3 h before sap collection. ABA concentration in extruded sap ([ABA](sap)) was compared with [ABA](solution). In low-volume extracts (less than 0.35 mm(3) cm(-2) leaf area) collected from leaves of well-watered plants, [ABA](sap) was close to [ABA](solution). For all lines, [ABA](sap) decreased with increasing V(sap). The same dilution effect was observed for leaves pressurized just after sampling on droughted plants, suggesting, as for detached leaves fed with ABA, that [ABA](sap) in low-volume extracts approximated well with the concentration of ABA entering leaves still attached on droughted plants. However, ABA-fed leaves sampled from droughted plants yielded higher [ABA](sap) than ABA-fed leaves sampled from well-watered plants. [ABA](sap) was also increased, although very slightly, when leaves were preincubated in highly enriched ABA solution. This indicates that some leaf ABA contributed to the ABA concentration returned in the extruded sap. Consistently, [ABA](sap) in medium-volume extracts (0.35-0.65 mm(3) cm(-2) leaf area) was lower for leaves sampled on under-producing lines than on the wild type. Despite these distortions between [ABA](solution) and [ABA](sap) in medium-volume extracts, stomatal conductance of ABA-fed leaves closely correlated with [ABA](sap) with a similar relationship in all cases, whilst relationships with [ABA](solution) were more scattered.     

Regulation of polyribosome formation and protein synthesis in the uterus. Effect of administration of graded doses of oestradiol-17β and actinomycin D on the amino acid-incorporation activity in vitro and the cytoplasmic concentration in vivo of polyribosomes

1. The effects of graded doses of oestradiol-17beta and actinomycin D, administered separately or together, on the amino acid-incorporation activity in vitro and the cytoplasmic concentration in vivo of uterine polyribosomes are described. Preparations of polyribosomes isolated from uteri of ovariectomized adult rats were determined for cytoplasmic concentration in vivo and assayed for [(14)C]leucine-incorporation activity in the cell-free system, exactly as described by Teng & Hamilton (1967b). 2. A minimal dose of 10mug of oestradiol-17beta administered for 10h was found to increase, by about 100%, both the amino acid-incorporation activity in vitro and the cytoplasmic concentration in vivo of the polyribosomes. A minimal dose of 250mug of actinomycin D administered for 10h was found to inhibit, by about 50%, the incorporation activity in vitro of the polyribosomes. All doses of the inhibitor administered for 10h failed to alter the cytoplasmic concentration in vivo of the polyribosomes. 3. A dose of 10mug of oestradiol-17beta restored to the control value the inhibitory effect of a dose of either 50 or 125mug of actinomycin D on the activity in vitro of the polyribosomes, at 10h after treatment with the inhibitor and the hormone. In these experiments, there was an increase of 60-100% in the cytoplasmic concentration in vivo of the polyribosomes. 4. A dose of 125mug of actinomycin D, administered to animals along with 10mug of oestradiol-17beta for 6-36h, abolished the hormone-induced enhancement of the incorporation activity in vitro, but did not prevent an increase of about 200% in the cytoplasmic concentration in vivo of the polyribosomes. However, treatment with 750mug of the inhibitor abolished both stimulatory effects of the hormone. 5. The results reported indicate that the stimulatory effects of oestradiol-17beta in vivo on the number and activity of the cytoplasmic polyribosomes in the uterus of the ovariectomized rat have different sensitivities to actinomycin D, but the primary molecular mechanisms responsible for the results are unknown. The major conclusion drawn is that the formation and appearance in the cytoplasm of newly formed polyribosomes are important features of the early action of oestrogen in the uterus.     

Phytochrome involvement in stomatal movement in Pisum sativum, Vicia faba and Pelargonium sp.

Red and blue light triggered the opening of isolated stomata of Pisum sativum L. cv. Peleg Alvador, Vicia faba L. (unknown cultivar) and Pelargonium sp. The stimulatory effect of short irradiation with red or blue light was reversed by a subsequent short irradiation with far-red light. In Pisum the stimulatory effect of a continuous irradiation with red or blue light was also abolished by a concomitant far-red light. In leaf pieces of P. sativum blue light was more effective than red, but not in isolated guard cells. In the presence of mesophyll, DCMU inhibited stomatal opening in red light more than in blue, and thus increased the relative response to blue light. This was less evident in isolated guard cells.     

Biparental inheritance of chloroplast DNA and the existence of heteroplasmic cells in alfalfa

Summary Mapping of chloroplast DNA (ctDNA) restriction fragment patterns from a chlorophyll deficient mutant and two phenotypically normal alfalfa genotypes (Medicago sativa L.) has demonstrated the existence of a distinct ctDNA genotype from each source. These unique restriction fragment patterns were utilized to identify maternal or paternal origin of ctDNA in hybrid plants from crosses involving the normal alfalfa genotypes as females and the yellow-green chlorophyll deficient sectors as males. Progeny from these crosses expressing the yellow-green sectored phenotypes contained paternal ctDNA in the chlorophyll deficient sectors and maternal ctDNA in the normal sectors, confirming biparental plastid inheritance. The existence of mixed cells containing both mutant and normal plastids at various stages of sorting-out was observed by transmission electron microscopy of mesophyll cells in mosaic tissue from hybrid plants. This observation verified the biparental transmission of plastids in alfalfa.     

叶绿素荧光技术在植物环境胁迫研究中的应用

近年来叶绿素荧光技术在植物,包括藻类对各种环境胁迫响应的机理和应用研究中起着越来越重要的作用．本文简述了这方面的部分工作和进展．     

Distribution of UV-shielding of the epidermis of sun and shade leaves of the beech (Fagus sylvatica L.) as monitored by multi-colour fluorescence imaging

Plants can protect against damaging ultraviolet (UV) radiation by accumulating UV-absorbing substances in the epidermis of the leaves. Sun and shade leaves of a free standing beech tree (Fagus sylvatica L.) were studied for the differences in UV-shielding of the epidermis by means of multi-colour fluorescence images taken with UV and blue excitation. The distribution of the fluorescence intensity was detected over intact leaves in the emission maxima in the blue at 440 nm (F440), in the green at 520 nm (F520), in the red at 690 nm (F690) and in the far red at 740 nm (F740). Images of the logarithmic ratio between F690 excited in the blue and the UV (log (^BF690/^UVF690)) were calculated representing the relative absorption of UV in the epidermis and thus the degree of UV-shielding. It was found that UV-shielding is stronger for sun leaves than for shade leaves and better for the upper (adaxial) leaf side than for the lower (abaxial) leaf side of both leaf types. Within one leaf the highest value for the ratio log (^BF690/^UVF690) and thus the highest UV-shielding was found at the leaf rim which in broad leaves contains young tissue.     

不同培养基对发菜细胞生长和光合活性的影响

研究测定了发菜(NostocflagelliformeBorn.etFlah.)细胞在不同培养基中的生长速率、光合作用和叶绿素荧光活性。结果显示培养11d后:Detmer培养基中叶绿素a的含量为1.08mg/L,Kratz-Myers培养基中叶绿素a的含量为1.87mg/L,水生104号培养基中叶绿素a的含量为1.21mg/L,BG11培养基中叶绿素a的含量为2.18mg/L,表明在BG11培养基中培养的细胞具有最高生长速率;与另外4种不同浓度的BG11培养基相比,上述BG11培养基培养的发菜具有最大的光合速率Pm(218.1μmolO2.mg-1chla.h-1)和最高的PSII光化学效率(Fv/Fm=0.349)。实验结果表明,BG11是适合发菜生长的培养基,对其光合作用和叶绿素荧光活性具有显著促进作用。     

Photosynthetic performance in Sphagnum transplanted along a latitudinal nitrogen deposition gradient

Increased N deposition in Europe has affected mire ecosystems. However, knowledge on the physiological responses is poor. We measured photosynthetic responses to increasing N deposition in two peatmoss species (Sphagnum balticum and Sphagnum fuscum) from a 3-year, north–south transplant experiment in northern Europe, covering a latitudinal N deposition gradient ranging from 0.28 g N m⁻² year⁻¹ in the north, to 1.49 g N m⁻² year⁻¹ in the south. The maximum photosynthetic rate (NP_max) increased southwards, and was mainly explained by tissue N concentration, secondly by allocation of N to the photosynthesis, and to a lesser degree by modified photosystem II activity (variable fluorescence/maximum fluorescence yield). Although climatic factors may have contributed, these results were most likely attributable to an increase in N deposition southwards. For S. fuscum, photosynthetic rate continued to increase up to a deposition level of 1.49 g N m⁻² year⁻¹, but for S. balticum it seemed to level out at 1.14 g N m⁻² year⁻¹. The results for S. balticum suggested that transplants from different origin (with low or intermediate N deposition) respond differently to high N deposition. This indicates that Sphagnum species may be able to adapt or physiologically adjust to high N deposition. Our results also suggest that S. balticum might be more sensitive to N deposition than S. fuscum. Surprisingly, NP_max was not (S. balticum), or only weakly (S. fuscum) correlated with biomass production, indicating that production is to a great extent is governed by factors other than the photosynthetic capacity.     

Antagonism between elevated CO2, nighttime warming,and summer drought reduces the robustness of PSII performance to freezing events

Plant responses to warming, elevated CO₂, and changes in summer precipitation patterns involve complex interactions. In this study we aim to reveal the single factor responses and their interactive effects on photosystem II (PSII) performance during an autumn-to-winter period. The study was carried out in the CLIMAITE multifactor experiment, which includes the combined impact of elevated CO₂ (free air carbon enrichment; CO₂), warming (passive nighttime warming; T) and summer drought (rain-excluding curtains; D) in a temperate heath ecosystem. PSII performance was probed by the effective quantum yield in light, F_v′/F_m′, using the pulse amplitude methodology, and the total performance index, PI_total, which integrate changes of the chlorophyll-a fluorescence transient including the maximal quantum yield in darkness, F_v/F_m.Decreasing temperature during autumn linearly reduced PI_total, both in the wavy hair-grass, Deschampsia flexuosa, and in the evergreen dwarf shrub common heather, Calluna vulgaris, and following freezing events the PI_total and F_v′/F_m′ were reduced even more. Contrary to expected, indirect effects of the previous summer drought reduced PSII performance before freezing events, particularly in Calluna. In combinations with elevated CO₂ interactive effects with drought, D × CO₂ and warming, T × D × CO₂, were negatively skewed and caused the reduction of PSII performance in both species after occurrence of freezing events. Neither passive nighttime warming nor elevated CO₂ as single factors reduced PSII performance via incomplete cold hardening as hypothesized. Instead, the passive nighttime warming strongly increased PSII performance, especially after freezing events, and when combined with elevated CO₂ a strongly skewed positive T × CO₂ interactive effect was seen. This indicates that these plants take advantage of the longer growing season induced by the warming in elevated CO₂ until a winter frost period becomes permanent. However, if previously exposed to summer drought this positive effect reverses via interactive D × CO₂ and T × D × CO₂ effects immediately after freezing events, causing the full combination of TDCO₂ not to differ from the control.In a future warmer climate with high CO₂ and summer drought, the occurrence of freezing events thus seem highly decisive for reducing PSII performance in the autumn-to-winter period. Such a reduced robustness of PSII performance may be highly decisive for the magnitude of the late season photosynthetic carbon uptake and reduce the growing season length in these temperate heath plants.     

金钟藤叶绿素荧光特征初探

利用叶绿素荧光技术初步观测丁金钟藤在不同作用光下的光合生理特征,并对其离体叶片在低温、高温及脱水胁迫下的光能利用状况作了比较。结果显示,随着作用光强的增加,叶片Fv＇/Fm＇、qP和ΦPSⅡ呈下降趋势,qN和NPQ表现为上升。离体叶片在5℃处理6h后,其Fv＇/Fm＇、qP和ΦPSⅡ高于25℃和45℃处理的,而NPQ在5℃和45℃处理6h后明显低于对照（25℃）,qN则略有降低。离体叶片脱水胁迫12h后,仍有一定的光能转化能力,但脱水24h和36h后,qP、ΦPSⅡ、qN、NPQ都明显下降。这表明金钟藤对于环境因子,如光强、温度及水分的变化具有较强的适应性,这可能是其在森林中能快速蔓延扩散的一个重要原因。     

Photoinhibition of photosynthesis in Lemna gibba as induced by the interaction between light and temperature. II. Photosynthetic electron transport

Photoinhibition of photosynthesis in Lemna gibba L. was induced by exposing intact plants to a high photosynthetic photon flux density of 1 750 μmol m⁻² s⁻¹ at a low temperature of 3°C. Subsequently isolated chloroplasts showed pronounced reductions in the capacity of whole chain electron transport, measured as Hill activity, and in the efficiency of electron transport to the primary electron acceptor Q of photosystem II, measured as variable chlorophyll fluorescence at 20°C. These changes proceeded with similar kinetics (probably of the first-order reaction), suggesting that the site of photoinhibition is in the electron transfer to Q. A partial uncoupling of the whole chain electron transport also occured. The capacity of electron transport mediated by photosystem I was unaffected. The extent of photoinhibition of photosynthetic electron transport, as produced by a 2 h exposure of L. gibba to three different combinations of photon flux density and temperature was studied. It was shown that intrinsically similar states of photoinhibition, on the evidence of their time courses of recovery, were induced by either a high photon flux density and 25°C or by a moderate photon flux density and 3°C.     

Physiological traits associated with heat tolerance in bread wheat (Triticum aestivum L.)

Field experiments for evaluating heat tolerance-related physiological traits were conducted for two consecutive years using a mapping population of recombinant inbred lines (RILs) from the cross RAJ4014/WH730. Chlorophyll content (Chl) and chlorophyll fluorescence (CFL) were recorded under timely sown (TS) and late sown (LS) conditions. Late sowing exposes the terminal stage of plants to high temperature stress. Pooled analysis showed that CFL and Chl differed significantly under TS and LS conditions. The mean value of CFL (Fv/Fm) and Chl under both timely and late sown conditions were used as physiological traits for association with markers. Regression analysis revealed significant association of microsatellite markers viz., Xpsp3094 and Xgwm131 with coefficients of determination (R²) values for CFL (Fv/Fm) and Chl as 12 and 8 %, respectively. The correlation between thousand grain weight (TGW) with Chl and CFL were 14 and 7 % and correlation between grain wt./spike with Chl and CFL were 15 and 8 %, respectively. The genotypes showing tolerance to terminal heat stress as manifested by low heat susceptibility index (HSI = 0.43) for thousand grain weight, were also found having very low Chl, HSI (−0.52). These results suggest that these physiological traits may be used as a secondary character for screening heat-tolerant genotypes.