温度变化对烟草光合作用光响应特征的影响

通过Li-6400光合测定系统控温,研究了大田条件下,烟草脚叶采烤期腰叶在17、20、25、30和35℃下的光合作用光响应特征。结果表明:随温度升高,净光合速率(Pn)、最大净光合速率(Pnmax)、初始斜率(α)和气孔导度(Gs)先上升后下降,在20℃下达最大值,35℃下净光合速率受强光的抑制作用明显;光补偿点(LCP)和暗呼吸速率(Rd)随温度升高而上升,但35℃下二者较30℃时有所下降;光饱和点(LSP)随温度升高而呈下降-上升-下降的变化,30℃和17℃时LSP较高;蒸腾速率(Tr)随温度上升而增强,水分利用效率(WUE)则随温度升高而下降,但20℃时水分利用效率在强光下明显较其他温度下的高。结果说明,20℃最适合烟草光合作用,此温度下气孔的水、气调节能力最强,温度高于30℃则对烟草光合作用不利。     

Effects of sodium chloride on tobacco plants

Abstract The effect of salinity on the growth and ion concentrations in a number of tobacco cultivars is described. Sodium chloride, at a concentration of 200 mol m^?3, hardly affected the fresh weight, but significantly reduced the dry weight. The difference in the response of fresh and dry weights to salt was due to a change in succulence (water per unit leaf area); the latter increased with increasing leaf Na⁺ and Cl^? concentration. Under saline conditions, increasing the external Na⁺: Ca^? ratio by decreasing the Ca²⁺ concentration increased the accumulation of Na⁺ and Cl^? into the leaf tissue.     

Decline of leaf hydraulic conductance with dehydration: relationship to leaf size and venation architecture

Across plant species, leaves vary enormously in their size and their venation architecture, of which one major function is to replace water lost to transpiration. The leaf hydraulic conductance (K(leaf)) represents the capacity of the transport system to deliver water, allowing stomata to remain open for photosynthesis. Previous studies showed that K(leaf) relates to vein density (vein length per area). Additionally, venation architecture determines the sensitivity of K(leaf) to damage; severing the midrib caused K(leaf) and gas exchange to decline, with lesser impacts in leaves with higher major vein density that provided more numerous water flow pathways around the damaged vein. Because xylem embolism during dehydration also reduces K(leaf), we hypothesized that higher major vein density would also reduce hydraulic vulnerability. Smaller leaves, which generally have higher major vein density, would thus have lower hydraulic vulnerability. Tests using simulations with a spatially explicit model confirmed that smaller leaves with higher major vein density were more tolerant of major vein embolism. Additionally, for 10 species ranging strongly in drought tolerance, hydraulic vulnerability, determined as the leaf water potential at 50% and 80% loss of K(leaf), was lower with greater major vein density and smaller leaf size (|r| = 0.85-0.90; P < 0.01). These relationships were independent of other aspects of physiological and morphological drought tolerance. These findings point to a new functional role of venation architecture and small leaf size in drought tolerance, potentially contributing to well-known biogeographic trends in leaf size.     

Direct creation of marker-free tobacco plants from agroinfiltrated leaf discs

Agroinfiltration is employed as a fast way to directly create marker-free transgenic tobacco plants. As an example for the efficiency of the method, Agrobacterium cells harboring a marker-free vector coding for β-glucuronidase (GUS) were infiltrated into the leaf discs of Nicotiana tabacum, which were then used as explants for marker-free plant regeneration by tissue culture. Through GUS staining, a large number of small calli were shown to be stably transformed on the treated leaf discs at 17 days after agroinfiltration. Most importantly, after continuous culture of the leaf discs until shoot regeneration, about 15% of the regenerants were proven to be transformants by polymerase chain reaction (PCR) analysis.     

Effects of low temperature on wheat leaf proteins

Finnish wheat cultivars, winter wheat ‘Vakka’ and spring wheat ‘Apu’, grown for 9 days at 25° and then for 52 days at 2–4°, were called ‘hardened’. Proteins and esterases of young leaves were resolved by polyacrylamide gel electrophoresis (PAGE), porosity gradient PAGE (poroPAGE), isoelectric focusing (PAGIF) between pH 3 and 9, and by Na-dodecylsulfate (SDS)-PAGE. Hardened and unhardened leaves have different protein patterns after PAGE, PAGIF, poroPAGE and SDS-PAGE, respectively, as well as for esterases after PAGE and PAGIF. The PAGIF patterns of esterases show distinct changes of two bands especially for hardened leaves of winter wheat, one appearing, the other one disappearing.     

Transgenic tobacco plants regenerated from leaf disks can be periclinal chimeras

Amongst rolC transgenic tobacco plants regenerated from leaf disks 6.5% are periclinal chimeras, i.e. plants with genetically different cell populations in different cell layers. The expression of the rolC gene of Agrobacterium rhizogenes causes a reduction in pigment content in leaves. The chimeric composition of the regenerated plants becomes thus apparent as light green leaf tissue in the transgenic region, tissue flanked by dark green wild-type sectors. Southern and northern blot analysis confirmed the chimeric nature of such plants. Investigation of selfed progeny of chimeric plants on selective media indicates that layer invasion in reproductive tissues can occur in tobacco early during the formation of the flower buds. The results show (1) that tobacco plants regenerated from leaf disks and grown on selective media have not necessarily the same clonal origin and (2) that they can give rise to non-transgenic offspring. The chimeric plants provide insight on the effect of rolC gene expression on microsporogenesis.     

Water stress-induced modifications of leaf hydraulic architecture in sunflower: co-ordination with gas exchange

The hydraulic architecture, water relationships, and gas exchange of leaves of sunflower plants, grown under different levels of water stress, were measured. Plants were either irrigated with tap water (controls) or with PEG600 solutions with osmotic potential of -0.4 and -0.8 MPa (PEG04 and PEG08 plants, respectively). Mature leaves were measured for hydraulic resistance (R(leaf)) before and after making several cuts across minor veins, thus getting the hydraulic resistance of the venation system (R(venation)). R(leaf) was nearly the same in controls and PEG04 plants but it was reduced by about 30% in PEG08 plants. On the contrary, R(venation) was lowest in controls and increased in PEG04 and PEG08 plants as a likely result of reduction in the diameter of the veins' conduits. As a consequence, the contribution of R(venation) to the overall R(leaf) markedly increased from controls to PEG08 plants. Leaf conductance to water vapour (g(L)) was highest in controls and significantly lower in PEG04 and PEG08 plants. Moreover, g(L) was correlated to R(venation) and to leaf water potential (psi(leaf)) with highly significant linear relationships. It is concluded that water stress has an important effect on the hydraulic construction of leaves. This, in turn, might prove to be a crucial factor in plant-water relationships and gas exchange under water stress conditions.     

Stomatal resistance,leaf water potential and hydraulic resistance of sugar beet plants

Stomatal resistance (r_L) and leaf water potential (Υ_L), soil moisture and the course of meteorological factors were measured in irrigated and non-irrigated sugar beet canopies during three years. By means of the canopy water balance equation, theoretical analysis of observed dependencies of stomatal resistance upon leaf water potential was made. The changes of r_L were not induced by the change of (Υ_L) but by that of external and internal factors, (Υ_L) correlates with. Therefore the empirical dependence of stomatal resistance upon leaf water potential cannot be generalized.     

Effects of temperature and light on the formation of chloroplast protrusions in leaf mesophyll cells of high alpine plants

Chloroplasts of many alpine plants have the ability to form marked, stroma-filled protrusions that do not contain thylakoids. Effects of temperature and light intensity on the frequency of chloroplasts with such protrusions in leaf mesophyll cells of nine different alpine plant species (Carex curvula All., Leontodon helveticus Merat., Oxyria digyna (L.) Hill., Poa alpina L. ssp. vivipara, Polygonum viviparum L., Ranunculus glacialis L., Ranunculus alpestris L., Silene acaulis L. and Soldanella pusilla Baumg.) covering seven different families were studied. Leaves were exposed to either darkness and a stepwise increase in temperature (10-38 degrees C) or to different light intensities (500 and 2000 micromol photons m(-2) s(-1)) and a constant temperature of 10 or 30 degrees C in a special temperature-regulated chamber. A chloroplast protrusions index characterising the relative proportion of chloroplasts with protrusions was defined. Seven of the nine species showed a significant increase in chloroplast protrusions when temperature was elevated to over 20 degrees C. In contrast, the light level did not generally affect the abundance of chloroplasts with protrusions. Chloroplast protrusions lead to a dynamic enlargement of the chloroplast surface area. They do not appear to be directly connected to a distinct photosystem II (PSII) (F(v)/F(m)) status and thus seem to be involved in secondary, not primary, photosynthetic processes.     

Expression of photosynthesis gene-promoter fusions in leaf epidermal cells of transgenic tobacco plants

Fusions of the promoter regions of the pea plasto-cyanin, pea ferredoxin: NADP⁺ reductase and tobacco rbcS genes to the β-glucuronidase (GUS) reporter gene have been introduced into tobacco via Agro-bacterium-mediated transformation, and epidermal peels of the lower leaf surface of tissue-cultured and greenhouse-grown plants examined histochemically for GUS activity. For each of the constructs, GUS was detected in epidermal cells as well as in stomatal guard cells. Epidermal peels from plants in tissue culture stained more readily than those from greenhouse-grown plants. Light and electron microscopy clearly demonstrated the presence of chloroplasts in epidermal cells of tobacco leaves. These results provide further evidence for the correlation between the presence of chloroplasts and the expression of nuclear genes for photosynthesis components.     

机械损伤对9种水生植物叶片的影响

水生植物叶片的功能性状特征与陆生植物有所不同,同时叶脉类型也显著影响叶片的功能性状。本研究选取9种具有不同叶脉类型的水生植物,通过对叶脉进行直接损伤,分析叶片性状(形态、色素含量和叶绿素荧光指标)在叶脉受损后的变化程度与叶脉类型的关系。结果显示:具有平行脉的3种水生植物对叶脉损伤具有较强的耐受性;具羽状脉的4种植物主脉受损后显著抑制叶片生长,而侧脉受损的影响在不同物种间有所不同,具有物种特异性。本研究可为大型湖泊水生植物修复的水生物种筛选提供参考。     

Effects of soil flooding on leaf gas exchange of tomato plants

Carbon dioxide and water vapor exchange of tomato (Lycopersicon esculentum Mill. cv Rheinlands Ruhm) leaves were measured before and after 24 h of soil flooding to characterize both stomatal and nonstomatal responses to the stress. Leaf epidermal conductance to water vapor decreased by 47% after flooding, accompanied by an increase in the sensitivity of stomata to changes in CO₂ concentration. Assimilation rates under ambient conditions fell by 27%, and the inhibition could not be overcome by elevated CO₂ partial pressures. Stomatal conductance limited the assimilation rate to approximately the same degree both before and after flooding. The reduction in photosynthetic capacity was not due to a decrease in apparent quantum yield or to an increase in photorespiration. The results were analyzed according to a recent model of photosynthesis, and possible mechanisms underlying the flooding effect are discussed.     

High-frequency generation of transgenic tobacco plants after modified leaf disk cocultivation withAgrobacterium tumefaciens

A modified protocol for theAgrobacterium tumefaciens-mediated transformation of tobacco (Nicotina tabacum L.) leaf disks was developed for greater recovery of transgenic plants. Modifications include transformation ofAgrobacterium by a freeze-thaw procedure, initial cocultivation of leaf disks andAgrobacterium under vacuum, subsequent growth with nurse cells for one week, rooting of shoots in medium lacking carbenicillin, longer, growth in rooting medium, and a shortened “hardening” step. By this procedure, an average of 1.3 kanamycin-resistant calli were obtained per leaf disk, and 38% of, the callus cultures used were regenerated to produce 133 independently transformed tobacco plants.     

Effects of temperature on the cytokinin requirement of tobacco calluses

A cytokinin-nonrequiring strain (T22) was isolated from a cytokinin-requiringcallus strain T2 of tobacco (Nicotiana tabacum var. Bright Yellow). Strain T22 grew rapidly on the medium without added kinetinat 26?C. But its growth was completely suppressed at 16?C. Thisgrowth suppression at 16?C was partially recoverable by supplyingkinetin. Benzyladenine, geranylaminopurine and 2-methyl-8-benzylamino-s-triazolo[l,5-a]pyrazinewere also effective in removing growth suppression at 16?C.Adenine, which was unable to remove growth suppression of T22at 16?C, promoted the growth of T2 at 26?C, but not at 16?C.Physiological differences between cytokinin-requiring and -nonrequiringcalluses are discussed. ¹Part II in the series "Studies, on Plant Tissue Cultures";for Part I, See Plant & Cell Physiol. 9: 103–114 (1968). (Received May 29, 1970; )     

成虫期温度对稻纵卷叶螟生殖特性的影响

温度是影响昆虫生殖的重要环境因子,本文通过成虫期不同日龄低温处理研究了温度对稻纵卷叶螟Cnaphalocrocis medinalis Guenée成虫生殖和寿命的影响。结果表明:羽化后1日龄15℃处理对稻纵卷叶螟雌蛾生殖有显著的促进作用,体现在成虫产卵显著提前,产卵量显著增加,首次产卵历期显著缩短,交配次数显著增加,交配率明显上升,而在其他日龄处理仅导致首次产卵历期显著缩短,对成虫其他生殖指标无显著影响。1日龄10℃处理对稻纵卷叶螟成虫生殖并没有显著影响,但显著缩短成虫的寿命。这些结果表明,1日龄是低温调控稻纵卷叶螟生殖的敏感时期,此时期15℃刺激能显著促进成虫生殖。     

Leaf temperature of desert sand dune plants: perspectives on the adaptability of leaf morphology

The leaf temperature of six annual and six perennial plant species was monitored during spring and summer on a sand dune ecosystem in the delta Mediterranean coast of Egypt. During winter, leaves of all tested perennial species attained temperatures higher than the air temperature at night and shortly after sunrise, with maximum leaf–air temperature differences reaching up to 8°C. The lowest differences were less than 1°C. Around noon, the leaves of several species attained temperatures lower than that of the air whereas others showed higher temperatures. The opposite was true during summer, when leaf temperatures were lower than air temperature. The maximum leaf–air temperature differences occurred after midnight towards sunrise and reached up to 10°C. The lowest differences were found around noon and were of less than 5°C. The annual plant species have more pronounced variations than perennials in their leaf temperatures during the night and for most of the day. The leaves were heated or cooled a few degrees above or below the air temperature. The results are discussed in relation to the morphological characters of the leaves. The variation in leaf temperature at different times of the day was significantly related to leaf morphology, specific leaf area, thickness, volume, leaf area index and the surrounding environment.     

Effects of water stress and rewatering on leaf water relations of lemon plants

Potted two-year-old lemon plants (Citrus limon (L.) Burm. fil.) cv. Fino, growing under field conditions were subjected to drought by withholding irrigation for 13 d. After that, plants were re-irrigated and the recovery was studied for 5 d. Control plants were daily irrigated maintaining the soil matric potential at about -30 kPa. Young leaves of control plants presented higher leaf conductance (g1) and lower midday leaf water potential (Ψmd) than mature ones. Young leaves also showed higher leaf water potential at the turgor loss point (Ψtlp) than mature leaves. In both leaf types g1 decreased with increased vapour pressure deficit of the atmosphere. From day 1 of the withholding water, predawn and midday leaf water potentials (Ψpd and Ψmd) decreased, reaching in both cases minimum values of -5.5 MPa, with no significant differences between mature and young leaves. Water stress induced stomatal closure, leaf rolling and partial defoliation. No osmotic adjustment was found in response to water stress in either leaf type, but both were able to enhance the cell wall elasticity (elastic adjustment). After rewatering, leaf water potential recovered quickly (within 2 d) but g1 did not. This revised version was published online in July 2006 with corrections to the Cover Date.