An Instrument for the Continuous Determination of Leaf Thickness Changes in the Field

The paper deals with the construction and use of an instrumentwhich measures changes in leaf thickness. Results obtained in the field with four tree species are presented.Changes in thickness were of an individual nature for each leaf;collectively the leaves of one tree species differed in theirthickness changes from those of others. Changes in leaf thickness were mainly due to changes in thevolumes of special water-storage tissues. Leaf water contentchanges and leaf thickness changes determined simultaneouslyin the laboratory were well correlated, provided that the thicknesschanges did not exceed those occuring m the field. Several of the factors which influenced changes in leaf thicknesswere measured.The march of leaf temperature was found to becorrelated most closely with the march of leaf thickness.     

The Effect of Light Intensity and Relative Humidity on Growth Rate and Root Respiration of Plantago lanceolata and Zea mays

Plants of Plantago lanceolata L. and Zea mays L., cv. ‘Campo’were grown at two levels of light intensity. Especially in theroots, the rate of dry matter accumulation decreased at lowlight intensity. The carbohydrate content of both roots andshoots of P. lanceolata was not affected by light intensity.The relative contribution of SHAM¹-sensitive respiration, thealternative chain, to total root respiration of both P. lanceolataand Z. mays, was not affected by light intensity during thedaytime. The alternative pathway was somewhat decreased at theend of the dark period, but not in the root tips (0–5mm) where it still contributed 56% in respiration. It was, therefore,concluded that photosynthesis is not a major factor in regulationof root growth in the species investigated. To see whether the effect of light intensity on root growthrate was via transpiration, plants of Z. mays were grown atdifferent air humidities. Both high humidity and low light intensityaffected the root morphology in such a way that the distancebetween the apex and the first laterals on the primary rootaxis increased. It is suggested that this effect on root morphologyis due to transpiration and the subsequent removal of root-producedinhibitors of lateral root growth; although light intensityalso affected the rate of dry matter accumulation of roots andthe rate was not affected by the humidity of the air. It is,therefore, concluded that the effect of light intensity on therate of dry matter accumulation of roots of Z. mays is not viaan effect on transpiration.     

Cuticular Conductance and the Humidity Response of Stomata

Meidner, H. 1986. Cuticular conductance and the humidity responseof stomata.—J. exp. Bot. 37: 517–525. Detailed measurements of cuticular vapour loss from leaves ofseveral species showed that cuticular conductance declined froman early morning maximum of 0?02 cm s^–1 to between 0?004and 0.005 cm scm s^–1 even in the absence of stomatal transpiration.Re-establishment of the maximum conductance occurred only ina humid atmosphere and when the xylem system was under pressure(simulated mild root pressure) Cuticular vapour loss alone is,therefore, unlikely to be the underlying mechanism of the humidityresponse of Stomata. Evidence for the existence of a humidity-sensing feed-forwardmechanism is discussed and it is shown that when detailed measurementsare made the humidity response is found to have two phases.This indicates a perturbation of the fine turgor balance betweenepidermat and guard cells that exists in a transpiring leaf.It is argued that the humidity response can be accounted forby reference to hydropassive movements which initiate a metabolicadjustment of the guard cells to altered evaporative demand. Key words: Cuticle, conductance, humidity, stomata, transpiration     

Female polymorphism, condition differences, and variation in male harassment and ambient temperature

Female polymorphism is considered to be maintained through negative frequency-dependent selection imposed by costly male harassment. However, few studies have questioned whether male harassment negatively affects female morph success and does so differently for female morphs, especially in the wild. In the present study, we quantified female morph condition (relative body mass and energy reserves) for a colour polymorphic damselfly under natural conditions and evaluated these measures against variation in proxies of male harassment (population density and operational sex ratio) and ambient temperature. Differences in protein content between female morphs were detected and the variation in condition could partly be explained from concomitant variation in proxies of male harassment. Specifically, the relationship between protein content and operational sex ratio differed between morphs in that the negative effect of male harassment was more pronounced in gynomorphs than in andromorphs. In addition, ambient temperature affected the body mass and protein content of female morphs differently, with andromorphs having higher condition values in favourable weather conditions, whereas, for gynomorphs, the patterns tended to be opposite. In conclusion, the results obtained in the present study suggest that male harassment negatively and differentially affects female morph success. Future studies should aim to elucidate whether the observed effects of ambient temperature contribute to the maintenance of the polymorphism.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 97 , 545–554.     

Constraints on home range behaviour affect nutritional condition in urban house sparrows (Passer domesticus)

In human‐dominated landscapes (semi)natural habitats are typically embedded in tracts of unsuitable habitat. Under such conditions, habitat characteristics and grain size of the surrounding landscape may affect how much food, and at what cost, is available for sedentary species with low home‐range plasticity. Here we combine behavioural radio‐tracking, feather ptilochronology, and landscape analysis to test how nutritional condition varies with home range size in 13 house sparrow [Passer domesticus (Linnaeus, 1758)] populations along an urban gradient. Urban individuals occupied smaller home ranges than conspecifics from rural areas, most distinctly if key cover was highly scattered. In urban plots, patch connectivity, home range sizes, and activity areas were positively correlated, indicating that individual ranging behaviour was related to the spatial distribution of suitable habitat. Urban House sparrows also showed the smallest feather growth bars, which were positively related to home range size at plot level. In contrast, growth bar widths and home range sizes were negatively related in rural populations, whereas in suburban populations, both variables varied independently. We conclude that individuals from progressively more built‐up areas show a restricted ability to adjust their daily ranging behaviour to the scattered distribution of critical resources. This may complement other putative causes of the widespread population decline of urban house sparrows. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 101 , 41–50.     

Transmissions- und rasterelektronen-mikroskopische Untersuchung an den Sinnesknospen der Tentakeln von Myxine glutinosa L. (Cyclostomata)

Sensory buds of different sizes have been found in the epidermis from the barbels of Myxine glutinosa. The electron microscopic investigations reveal their composition as one type of receptor cells and two types of supporting cells. The receptor cells have apical stereocilia with filamentous internal structure and there are microvilli on the supporting cells. The cytoplasma of the receptor cells contain fibrils and fibril bundles. The sensory buds are innervated by a nerve plexus below the basal lamina with nerve endings between the basal cells, which lie below the sensory buds. A comparison with sensory buds in some other vertebrates is drawn.     

Stomatal Responses to Humidity and the Water Potentials of Epidermal and Mesophyll Tissue

Effects of ambient humidity on relative water contents (RWC)and water potentials were measured separately for epidermaland mesophyll tissues in leaves of two species. Water potentialsdid not always change in the same direction as RWC within thesame tissue and rarely were the changes in water potential andRWC of one tissue correlated with those of the other. The natureof the humidity responses of stomata in certain species is discussedin relation to these results and to the anatomical propertiesof epidermal tissues.