Relationship between fern development and CAM in Pyrrosia piloselloides (L.) Price

Pyrrosia piloselloides (L.) Price is a constitutive CAM plant in the sporophytic phase of its life-cycle. Newly developed sporophytes, still attached to the gametophytes, showed signs of CAM expression in terms of diurnal changes in titratable acidity of the tissues. The gametophytes did not exhibit CAM. This revised version was published online in June 2006 with corrections to the Cover Date.     

EXPRESSION OF cfos IN THE MEDULLA OBLONGATA AFTER CAROTID BARORECEPTOR ACTIVATION BYELEVATED INTRASINUS PRESSURE AND ADENOSINE

在１４只隔离灌流颈动脉窦区的大鼠,观察了窦内压（ＩＳＰ）升高和灌流腺苷（ａｄｅｎｏｓｉｎｅ,Ａｄｏ）激活压力感受器时延髓内ｃｆｏｓ蛋白的表达。结果显示：在孤束核、最后区、延髓腹外侧头端区和中缝苍白核可见Ｆｏｓ蛋白样免疫阳性反应（ＦＬＩ）神经元分布,且其数量随ＩＳＰ升高而增多。在给定ＩＳＰ下,颈动脉窦内灌流Ａｄｏ,可使上述区域中ＦＬＩ表达明显增多。根据以上结果,得出如下结论：ｃｆｏｓ在压力感受器反射延髓通路中的表达,可由ＩＳＰ增高和灌流Ａｄｏ而增强,表明Ａｄｏ对压力感受器反射有易化作用。     

ANTIPYRETIC ACTION OF DEXAMETHASONE ON EGTAZIC ACIDINDUCED FEVER IN RABBITS

本文用脑室灌注和Ｆｕｒａ２测定细胞内游离钙技术观察了地塞米松（ｄｅｘａｍｅｔｈａｓｏｎｅ,ＤＥＸ）对家兔乙二醇双（２氨基乙醚）四乙酸性发热效应和下丘脑细胞内游离钙浓度（［Ｃａ２＋］ｉ）的影响,借此深入探讨地塞米松解热作用的中枢机制。结果发现：脑室灌注乙二醇双（２氨基乙醚）四乙酸（０６ｎｍｏｌ）引起家兔结肠温度明显升高,静脉注射地塞米松（５ｍｇ／ｋｇ）显著抑制家兔乙二醇双（２氨基乙醚）四乙酸性发热,地塞米松（６０～１２０μｍｏｌ／Ｌ）并不影响下丘脑细胞内［Ｃａ２＋］ｉ,而事先脑室灌注抑制基因转录的放线菌素Ｄ（３ｎｍｏｌ）则完全取消了地塞米松对乙二醇双（２氨基乙醚）四乙酸性发热的解热作用。这些结果提示：地塞米松显著抑制家兔乙二醇双（２氨基乙醚）四乙酸性发热,其机制与地塞米松激活脑内某些基因的表达有关,而与下丘脑神经细胞跨膜钙离子流无关。     

Response to Temperature in a Stand of Pearl Millet (Pennisetum typhoides S. & H.): 4. EXTENSION OF INDIVIDUAL LEAVES

The leaf extension rate of millet plants was measured with auxanometersin temperature-controlled glasshouses. Temperature was the dominantenvironmental factor governing the rate of leaf extension. Theobserved linear relation between extension rate and meristemtemperature had a base temperature of 10 ?C and a less clearlydefined optimum of about 30–32 ?C. Leaf growth was expressed as extension per unit thermal time,mm (?C h)^–1, to examine the influence of saturation deficit,irradiance and ontogeny at different temperatures. Leaf extensionwas independent of saturation deficit below 3.0 kPA. Irradiance,ranging from 4–16 MJ m^–2 d^–1, had a greaterinfluence on the first five leaves than the subsequent onesbut there was a large effect of leaf position. The results arediscussed in relation to the growth of crop leaves in a tropicalclimate. Key words: Leaf extension, Millet, Temperature     

Response to Saturation Deficit of Leaf Extension in a Stand of Pearl Millet (Pennisetum typhoides S. & H.)I: I. INTERACTION WITH TEMPERATURE

Thermal time is used to analyse hourly differences in leaf extensionrate of pearl millet. The procedure enables the effects of theenvironment on leaf extension to be examined when temperatureis varying. The analysis was made on the results of two experimentsin which saturation vapour pressure deficit (SD) was controlledor allowed to vary with air temperature. In all treatments,temperature was the major environmental factor governing therate of leaf extension. The effect of SD was small in one experimentand negligible in the other. In the former, leaf extension wasalso limited by another factor, probably irradiance. Key words: Extension, Saturation deficit, Millet     

The Response of Groundnut (Arachis hypogaea L.) to Timing of Irrigation: II. 14C-PARTITIONING AND PLANT WATER STATUS

Finite quantities of water were applied at different growthstages of groundnut stands (Arachis hypogaea L.) grown in controlledenvironment glasshouses. Soil moisture deficits were imposedbetween sowing and pod initiation or between pod initiationand final harvest by withholding or applying water. Effectson assimilate production and partitioning and plant water relationswere examined. Leaves were the primary sites of ¹⁴CO₂ fixation, though theircontribution generally declined late in the season, whereasfixation by stems was initially low but increased sharply whenstress was released in the late-irrigated stands. ¹⁴C-fixationby stem apices and pegs also rose sharply following irrigationof the late-stressed stands. Leaves were the primary source of assimilates, though translocationtended to decrease as the season progressed, even in the late-irrigatedstands. Stems were initially the major sinks, but their sinkactivity disappeared almost completely when stress was releasedin the late-irrigated stands. Assimilate import by stem apicesdeclined progressively and pod sink activity was negligiblein the late-stressed stand, but both increased markedly whenearly-season stress was released. Leaf water status showed marked diurnal variation, whereas pegsshowed less variation and maintained much higher turgor levels,largely because of their lower solute potentials. Marked osmoticadjustment occurred in expanding but not in mature leaves, allowingthem to maintain higher turgor levels during periods of severestress. This adjustment was rapidly lost when stress was released.The observed changes in assimilate production and partitioningpreceded detectable changes in bulk turgor levels. Implications for growth, development and yield are discussed. Key words: Groundnut, irrigation, partitioning, water status     

In situ Studies of Crassulacean Acid Metobolism in Drymoglossum piloselloides, an Epiphytic Fern of the Humid Tropics

This paper reports autecological field-studies in Singaporeon Drymoglossum piloselloides (L.) Presl., an epiphytic fernof the humid tropics which is capable of performing Crassulaceanacid metabolism (CAM). As indicated by the gas exchange patternsand by the occurrence of a diurnal malic acid rhythm, the plantalso features CAM in situ at its natural sites. Both in well-wateredand in naturally droughted plants external CO₂ was taken upsolely during the night. Water stress decreased nocturnal CO₂uptake,but left the synthesis and storage of malic acid unaffected.This indicates that CO₂ recycling of respiratory CO₂ by CAMis ecophysiologically important at the high night temperaturestypical of the tropical habitats of the fern. The plants showeda diel fluctuation of cell-sap osmotic pressure which paralleledthat of malic acid, while the fluctuation of the xylem tensionfollowed the curve of transpiration more closely than it followedthat of the malic acid content. CAM in D. piloselloides wasclearly not limited by natural access to mineral ions and nitrogen.It is concluded that the ecophysiological advantage of CAM forD. piloselloides lies in a better water use efficiency as comparedwith C₃ ferns and in the salvaging of carbon by CO₂ recycling. Key words: CAM, epiphytic ferns, gas exchange, water relations     

Influence of Saturation Deficit on Leaf Production and Expafision in Stands of Groundnut-{Arachis hypogaea L.) Grown Without Irrigation

The response of leaf area expansion to atmospheric saturationdeficit (SD) and soil moisture deficit was examined in termsof leaf water potential (₁) and turgor potential (_p), as partof a wider study of the effects of SD on groundnut growth. Standsof plants were grown at four levels of SD and without irrigationin controlled environment glasshouses. A fifth stand was grownat low SD on soil kept irrigated to field capacity. Large saturation deficits accelerated the depletion of soilmoisture reserves in the unirrigated stands and greatly reducedleaf area index, particularly in the driest treatment. Leafnumber per plant and leaf size both decreased as SD increased,but the effect on leaf size was greater than on number. SD hadless effect than soil water deficit on leaf production. Turgorpotential and leaf extension rate (R) were both reduced at highsaturation deficits and R was linearly related to _p between0900 and 1600 h. However, leaf extension rate and turgor potentialwere poorly correlated between 0400 and 0700 h in the driesttreatment. Arachis hypogaea L., groundnut, saturation deficit, leaf growth, canopy development     

POTENTIATION OF CAFFEINEINDUCED CONTRACTURE BY RAISING EXTRACELLULAR POTASSIUM IN FROG SKELETAL MUSCLE

用蛙胫前肌小束为材料,研究了提高胞外钾［Ｋ＋］Ｏ对咖啡因挛缩的作用。［Ｋ＋］Ｏ从２ｍｍｏｌ／Ｌ提高到１０或２５ｍｍｏｌ／Ｌ,由３ｍｍｏｌ／Ｌ咖啡因引起的挛缩明显增强。以ＰＫＣ／ＰＣ（ＰＫＣ和ＰＣ分别为在高钾和正常钾条件下的咖啡因挛缩）表示的咖啡因挛缩增强,依赖［Ｋ＋］Ｏ和高钾作用时间。随着１０ｍｍｏｌ／Ｌ［Ｋ＋］Ｏ作用时间延长,直至１０ｍｉｎ,增强逐渐增加。但是,２５ｍｍｏｌ／Ｌ［Ｋ＋］Ｏ作用１ｍｉｎ时增强达到最大,然后下降到对照。ＰＫＣ／ＰＣ变化时程不能用高钾引起的去极化解释,而与由相似［Ｋ＋］Ｏ引起的胞浆自由钙变化时程相符。提示,至少在蛙骨骼肌,高钾引起的咖啡因挛缩增强主要是由胞浆自由钙升高引起的。     

Assimilate Distribution in Poa annua L.

The carbon economy of a flowering tiller of Poa annua L. hasbeen examined over the period from inflorescence emergence tograin shedding. The total import of ¹⁴C by the inflorescencereached a maximum at late grain filling but the relative importof assimilate was greatest 14 days after its appearance andrepresented 20–25 per cent of that assimilated by theinflorescence itself. The inflorescence continued to be an importantassimilatory organ after grain ripening when it exported morethan 50 per cent of its assimilate to the stem, roots and othertillers. The patterns of distribution of assimilates from the youngestuppermost and the oldest green leaf of the reproductive tillerwere largely determined by the stage of development of the inflorescence.The youngest leaf mainly supported the inflorescence up to theend of the grain-filling stage but then supplied assimilatesbasally to the roots and adjacent tillers. The oldest greenleaf supported the growth of the stem and the inflorescenceup to anthesis but after this supplied assimilates mainly tothe roots and tillers. Removal of grains or the entire inflorescence only 1 h beforesupplying ¹⁴CO₂ greatly reduced the rate of fixation of ¹⁴CO₂and the export of radiocarbon, as well as changing the patternof distribution of assimilates within the plant. The significanceof these results is discussed and comparisons made with cerealsand perennial grasses.