Air humidity as key determinant of morphogenesis and productivity of the rare temperate woodland fern Polystichum braunii

(1) Most ferns are restricted to moist and shady habitats, but it is not known whether soil moisture or atmospheric water status are decisive limiting factors, or if both are equally important. (2) Using the rare temperate woodland fern Polystichum braunii, we conducted a three‐factorial climate chamber experiment (soil moisture (SM) × air humidity (RH) × air temperature (T)) to test the hypotheses that: (i) atmospheric water status (RH) exerts a similarly large influence on the fern's biology as soil moisture, and (ii) both a reduction in RH and an increase in air temperature reduce vigour and growth. (3) Nine of 11 morphological, physiological and growth‐related traits were significantly influenced by an increase in RH from 65% to 95%, leading to higher leaf conductance, increased above‐ and belowground productivity, higher fertility, more epidermal trichomes and fewer leaf deformities under high air humidity. In contrast, soil moisture variation (from 66% to 70% in the moist to ca. 42% in the dry treatment) influenced only one trait (specific leaf area), and temperature variation (15 °C versus 19 °C during daytime) only three traits (leaf conductance, root/shoot ratio, specific leaf area); RH was the only factor affecting productivity. (4) This study is the first experimental proof for a soil moisture‐independent air humidity effect on the growth of terrestrial woodland ferns. P. braunii appears to be an air humidity hygrophyte that, whithin the range of realistic environmental conditions set in this study, suffers more from a reduction in RH than in soil moisture. A climate warming‐related increase in summer temperatures, however, seems not to directly threaten this endangered species.     

Dynamical systems analysis of arterial blood pressure signals in relation to heart rate fluctuations in chick embryos

We attempted a new approach based on a modern dynamical system theory to reconstruct the arterial blood pressure signals in relation to heart rate fluctuations of developing chick embryos. The dynamical systems approach in general is to model a phenomenon that is presented by a single time series record and approximate the dynamical property (e.g. heart rate fluctuations) of a system based only on information contained in a single-variable (arterial blood pressure) of the system. The time-series data of the arterial blood pressure was reconstructed in 3-dimensional space to draw characteristic orbits. Since the reconstructed orbits of the blood pressure should retain information contained in the pressure signals, we attempted to derive instantaneous heart rate (IHR) from the reconstructed orbits. The derived IHR presenting HR fluctuations coincided well with the IHR obtained conventionally from the peak-to-peak time intervals of the maximum blood pressure. Movements of the reconstructed orbits of the arterial blood pressure in 3-dimensional space reflected HR fluctuations (i.e. transient decelerations and accelerations).     

Effects of oxygen partial pressure and combined nitrogen on N2-fixation (C2H2) associated withZea mays and other gramineous species

Summary The objectives of this investigation were to determine the effects of oxygen partial pressure (pO₂) and combined nitrogen (NH ₄ ⁺ ) on rates of acetylene reduction (AR) associated with roots of intact corn, sorghum, and pearl millet plants. Soil-grown plants were carefully removed from soil and incubated hydroponically with the root system enclosed in a plastic cylinder; the tops were left exposed to ambient conditions. Oxygen concentrations around the root systems were controlled by sparging the nutrient solution with known quantities of O₂ in N₂. Ammonium nitrogen was added to the nutrient solution following establishment of AR rates to determine its effect on rates of N₂-fixation (AR). Substantial AR rates (0.1–1.5 mol C₂H₄ g dry wt^–1 h^–1) were associated with roots exposed to 0–2% O₂ (v/v) (0.0–2.02 kPa) in N₂ following at 12–24 h period of exposure to the reduced oxygen tension. Root systems exposed to air failed to demonstrate AR while those exposed to 100% N₂ showed lower activity than those at reduced pO₂ values. Addition of NH ₄ ⁺ (10–20 g N ml^–1 of nutrient solution) reduced AR by 75–90% within 24 h after addition. Oxygen uptake by roots exposed to low pO₂ was substantially reduced.     

虾塘养殖中后期微型浮游动物的摄食压力

2008年8月底到10月初,用现场稀释法对虾塘中≤200 μm、≤100 μm和≤20 μm 3个粒级的微型浮游动物对浮游植物的摄食压力进行了研究。共进行了三次培养实验,结果表明：浮游植物的生长率为0.0834～0.4498 d-1,微型浮游动物的摄食率为0.1212～0.2998 d-1,微型浮游动物摄食率对浮游植物生长率比值(g:k)为0.4271～3.4901,占浮游植物现存量的11.41%～25.90%,对初级生产力的摄食压力为48.20%～314.69%。≤20 μm微型浮游动物的摄食率、对浮游植物现存量和初级生产力的摄食压力,占微型浮游动物(≤200 μm)的相关比例范围为73.85%～97.69%、76.67%～97.91%、78.87%～98.59%。这表明≤20 μm微型浮游动物比≥20 μm的微型浮游动物在对虾养殖中后期虾塘能量流动和物质循环方面起到更重要的作用。     

电刺激猫小脑顶核对动脉血压和肾交感神经放电的影响

在38只麻醉及人工呼吸的猫,观察到电刺激小脑顶核嘴侧部能引起动脉血压显著升高;肾交感神经放电于刺激期间显著增加。去缓冲神经对刺激顶核所引起的血压反应的幅度和肾交感神经放电均无明显影响,但可明显延长血压反应升高相以及血压恢复期的时间。静脉注射氯庄定引起血压降低、心率减慢及肾交感神经放电的抑制,并能减弱刺激顶核引起的血压反应,但增强了刺激顶核引起的肾神经放电的变化。电解损毁延髓腹外侧面引起血压降低及肾交感神经放电的抑制,然而无论单侧还是双侧损毁延髓腹外侧面都不能阻断刺激顶核所引起的血压和肾交感神经放电的反应。以上结果表明,电刺激顶核能引起明显的心血管反应,其反应的下行性通路可能不通过延髓腹外侧面。     

Cell wall synthesis in cotton roots after infection with Fusarium oxysporum

Fusarium oxysporum f. sp. vasinfectum penetration hyphae infect living cells in the meristematic zone of cotton (Gossypium barbadense L.) roots. We characterized wall modifications induced by the fungus during infection of the protodermis using antibodies against callose, arabinogalactan-proteins, xyloglucan, pectin, polygalacturonic acid and rhamnogalacturonan I in high-pressure frozen, freeze-substituted root tissue. Using quantitative immunogold labelling we compared the cell walls before and after hyphal contact, cell plates with plasmodesmata during cytokinesis, and wall appositions induced by fungal contact. In the already-existing wall, fungal contact induced only minor modifications such as an increase of xyloglucan epitopes. Wall appositions mostly exhibited epitopes similar to the cell plate except that wall appositions had a much higher callose content. This study shows that wall appositions induced by Fusarium oxysporum hyphae are the result of normal cell wall synthesis and the addition of large amounts of callose. The appositions do not stop fungal growth.     

心肺压力感受器持续卸荷对前臂血流、血管阻力及心率变异性谱的影响

低压值下体负压（ＬＢＮＰ）可仅使心肺压力感受器卸荷。采用－２ｋＰａＬＢＮＰ实验结果表明：ＬＢＮＰ既不引起动脉血压变化,也不引起心率改变,但却引起基础胸阻抗（Ｚ。）从对照的２１．８±０．４升高到２２．５±０．５Ω（Ｐ＜０．０１）,前臂血管阻力（ＦＶＲ）从１２．３±０．９升高到１９．９±１．４Ｕ（Ｐ＜０．０１）,前臂血流（ＦＢＦ）从对照时７．１±０．５降低到４．３±０．３ｍｌ·ｍｉｎ￣（－１）·１００ｍｌ￣（－１）,心率变异性谱（ＨＲＶ）未发生任何变化,即心肺压力感受器卸荷时心脏自主神经活动水平与均衡性不受影响。由于ＦＶＲ和ＦＢＦ的变化可间接反映外周血管交感传出活动水平,上述实验结果提示,心肺压力感受器对外周血管及心脏自主神经活动的调节可能存在机能分化现象。     

倍增CO2分压对水稻和矶子草冠层光合潜力的影响

倍增CO2分压增高水稻的光饱和光合速率、表观量子产率和光能转换效率,而在倍增CO2分压下矶子草的相关光合参数降低,既水稻对高CO2分压表现为正响应,而矶子草在高CO2下光合作用下调。在倍增CO2分压下,水稻的Rubisco羧化速率和氧化速率均见增高,而矶子草在高CO2分压下,Rubisco羧化速率降低,而氧化速率略见增高。倍增CO2分压并不明显改变水稻的不包括光呼吸的CO2补偿点г^*,但矶子草г^*略见增高。在高CO2分压下可能改变矶子草Rubisco生化特性。倍增CO2分压降低两种供试植物的光下呼吸速率。水稻在倍增CO2分压下其Rubisco最大羧化速率(Vc max)和最大电子传递速率(Jmax)分别增高9．3％和20．7％,而矶子草在高CO2分压下则分别降低5．7％和3％。在倍增CO2分压下水稻的净光合量增高约5％,而矶子草则降低13％,植物种的不同特性可能影响植物在倍增CO2下的碳积累。随着全球气候变化和大气CO2,分压增高,将有利于发挥水稻高光合产率的优势,由于矶子草在高CO2分压下碳积累减少,从而可能限制其生长。大气CO2分压增高可能改变目前的水稻与杂草的生态关系而有利于控制杂草和改善田间耕作。     

Increased insulin-like growth factor-I gene expression precedes left ventricular cardiomyocyte hypertrophy in a rapidly-hypertrophying rat model system

Chronic pressure overload leads to an increase in the size, i.e. hypertrophy, of cardiomyocytes in the heart. However, the molecular mechanisms underlying this hypertrophy are not understood. Insulin-like growth factor-I (IGF-I) synthesized locally in the heart is known to be associated with the hypertrophic process. So far, however, cardiac IGF-I gene expression in the widely used rat model system has only been shown to be increased when the hypertrophy induced by pressure-overload was already established. Therefore, the question of whether IGF-I serves as an initiating or early-enhancing factor for the cardiac hypertrophy remains unanswered. Here, cardiac hypertension and hypertrophy were rapidly induced in the rat by complete constriction of the abdominal aorta between the origins of the renal arteries. Carotid arterial systolic blood pressure remained unchanged in sham rats but increased rapidly in the pressure-overloaded constricted rats with a sustained hypertension established by 3 days. Hypertrophy of left ventricular (LV) cardiomyocytes in constricted rats also occurred by 3 days. However, this hypertrophy was preceded by increases in LV IGF-I mRNA and protein which occurred within 1 day. These results support the hypothesis that cardiac-synthesized IGF-I is an initiating or early-enhancing factor for hypertrophy of LV cardiomyocytes.     

Stomatal response to humidity in a sugarcane field: simultaneous porometric and micrometeorological measurements*

Abstract. Gas exchange data obtained with wellventilated leaf cuvettes provide clear evidence of a stomatal response to leaf-air vapour pressure difference (V). In contrast, remotely sensed leaf temperatures with specific assumptions regarding canopy boundary layer characteristics, have been interpreted to mean that stomata do not respond to V. We address this apparent discrepancy in a sugarcane field by simultaneous application of a single-leaf, porometric technique and a whole-canopy, Bowen ratioenergy balance technique. These methods indicated significant stomatal response to V in well-irrigated sugarcane. Stomatal responses to V in the field were obscured by strong covariance of major environmental parameters so that opening responses to light and closing responses to V tended to offset each other. Low boundary layer conductance significantly uncoupled V at the leaf surface (V_s) from V determined in the bulk atmosphere (V_a). This reduced the range of the stimulus, V_s, thereby reducing the range of the stomatal response, without indicating low stomatal sensitivity to V. Stomatal responses to V_a may be smaller than expected from V response curves in cuvettes, since V_s rather than the conventionally measured V_a is analogous to V in a well-stirred cuvette. Recently published conclusions that remotely sensed canopy temperatures are inconsistent with stomatal response to V may be based on erroneous estimates of canopy boundary layer conductance and thus of V_s, use of air saturation deficit rather than V to express evaporative demand, and investigation at higher levels of evaporative demand than those eliciting maximal stomatal response.