Whole-plant ABA flux and the regulation of water loss in Cedrella odorata

Three-month-old Cedrella odorata seedlings were exposed to a soil-drying treatment. During this period, xylem sap was periodically collected from the plant by applying pneumatic pressure to the roots. This also allowed whole-plant water status to be measured by recording the balancing pressure applied. The concentration of ABA in xylem sap (C) was related to the whole-plant transpiration rate (V) which was measured with a sap flow gauge. The analysis of these paired measurements centred on how the reciprocal of C (R) varied with respect to V. This revealed that (1) the observed increases in C could not be explained by the reductions in V alone, (2) initially, decreases in V were associated with proportional increases in the whole-plant ABA flux (M), and (3) this relationship broke down at low values of V since zero flow was associated with a finite value for C estimated to be 41 pmol ABA mmol^?1 H₂O. A simple static model is developed from the observations that is able to explain the data well, and the results are discussed in terms of the effects of ABA on stomatal conductance (g_sw).     

Mouthparts in Leptotrombidium larvae (Acariformes: Trombiculidae)

Mouthparts of Leptotrombidium larvae (Acariformes: Trombiculidae), potential vectors of tsutsugamushi disease agents, were studied in detail using light microscopy, scanning electron microscopy, and transmission electron microscopy. The mouthparts incorporated within the pseudotagma gnathosoma are composed of the infracapitulum ventrally and the chelicerae dorsally. The ventral wall of the infracapitulum is formed by a wide mentum posteriorly and a narrowed malapophysis anteriorly. The malapophysis firmly envelops the distal cheliceral portions by its lateral walls. The lateral lips of the malapophysis are flexible structures hiding the cheliceral blades in inactive condition and turning back forming a type of temporary sucker closely applied to the host skin during feeding. The roof of the infracapitulum is formed by a weakly sclerotized labrum anteriorly and a cervix with the capitular apodemes extending posteriorly. The labral muscles are lacking. The capitular apodemes serve as origin for pharyngeal dilators running to the dorsal wall of the pharynx fused with the bottom of the infracapitulum. The basal cheliceral segments are separated from each other besides the very posterior portions where they are movably joined by the inner walls. The sigmoid pieces serve for insertion of the cheliceral elevators originating at the posterior portions of the basal segments. The movable digits reveal the solid basal sclerite and the cheliceral blade curved upward with a tricuspid cap on its tip. Dendrites of nerve cells run along the digits to their tips. The ganglia are placed within the basal segments just behind the movable digits. The chelicerae also reveal well developed flexible fixed digits overhanging the basal portions of the blades. The gnathosoma possesses several sets of extrinsic muscles originating at the scutum and at the soft cuticle behind it. Laterally, the gnathosoma bears five‐segmented palps with a trifurcate palpal claw. J. Morphol. 277:424–444, 2016. © 2016 Wiley Periodicals, Inc.     

Hydraulic conductance, stomatal conductance, and maximal photosynthetic rate in bean leaves

A positive correlation was found between steady state values of hydraulic (L _pA) and stomatal conductance (g _s) of French bean leaves: both were lower in the dark than in the light and lower in water-deficient plants than in the well-watered ones. The relative rate of stomatal opening after a pressure rise in the xylem was also positively related to L _pA. The L _pA and g _s were both related to the maximal photosynthetic rate at saturating CO2 concentrations. This revised version was published online in June 2006 with corrections to the Cover Date.     

Comparative morphology of the foliage leaf epidermis, with emphasis on papillae characters, in key taxa of woody bamboos of the Asian tropics (Poaceae: Bambusoideae)

The foliage leaf epidermis of 35 species representing 12 key genera of woody bamboos of the Asian tropics was investigated using light and scanning electron microscopy. The results indicated that papillae forms and distributional patterns around the stomatal apparatus of the abaxial foliage leaf epidermis were usually constant and were of great taxonomic significance at the specific and generic levels. However, papillae characters were not suitable for dividing subtribes within woody bamboos of the Asian tropics. On the basis of papillae characters, Schizostachyum s.s. and Cephalostachyum were confirmed, but their delimitations should be modified. The transfer of Leptocanna chinensis and Schizostachyum sanguineum into Cephalostachyum was supported, and Cephalostachyum virgatum and C .  pergracile were confirmed to be members of Schizostachyum s.s. The subtribe Racemobambosinae did not obtain support and Racemobambos appeared to be better placed in subtribe Bambusinae. Neomicrocalamus was supported as a close relative and better treated as a synonym of Racemobambos . Gigantochloa was closely related to Dendrocalamus .  © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society , 2008, 156 , 411–423.     

Unusual Structures in the Flagellar Apparatus of a Strain of Trypanosoma cruzi*

Certain structures, associated with the flagellum, and which had hitherto been described as appearing occasionally in some species of trypanosomes, were found very frequently in epimastigote forms of strain F of Trypanosoma cruzi: (a) a group of tubular elements in an electron-dense mass enclosed within a swelling of the flagellar membrane as the flagellum emerges from its reservoir; (b) an expansion of the flagellar membrane at the point of the above swelling, which in cross-sections appears as a ring; and (c) an electron dense band in the body of the organism alongside the border of the flagellar pocket. The possible significance of these structures and the fact that so far they have been found only in one strain of T. cruzi are discussed.     

The p24 family and selective transport processes at the ER—Golgi interface

The secretory pathway is of vital importance for eukaryotic cells and has a pivotal role in the synthesis, sorting, processing and secretion of a large variety of bioactive molecules involved in intercellular communication. One of the key processes in the secretory pathway concerns the transport of cargo proteins from the ER (endoplasmic reticulum) to the Golgi. Type‐I transmembrane proteins of ～24 kDa are abundantly present in the membranes of the early secretory pathway, and bind the COPI and COPII coat complexes that cover vesicles travelling between the membranes. These p24 proteins are thought to play an important role in the selective transport processes at the ER—Golgi interface, although their exact functioning is still obscure. One model proposes that p24 proteins couple cargo selection in the lumen with vesicle coat recruitment in the cytosol. Alternatively, p24 proteins may furnish subcompartments of the secretory pathway with the correct subsets of machinery proteins. Here we review the current knowledge of the p24 proteins and the various roles proposed for the p24 family members.     

Traction fibres in chromosome movement: the pros and cons

The current discussion on the mechanism of chromosome movement in anaphase is dominated by a new hypothesis assuming active movement of the chromosome along stationary kinetochore microtubules. The aim of this article is to call attention to several older as well as to more recent observations on spindle structural dynamics and microtubule rearrangements which, in the author's opinion, cannot be explained by the new model. In fact, the observations seem to be more consistent with the classical concept of a traction fibre. For this reason, these observations should not be disregarded.     

INBREEDING DEPRESSION IN MORPHOLOGICAL AND PHYSIOLOGICAL TRAITS OF SCHIEDEA LYDGATEI (CARYOPHYLLACEAE) IN TWO ENVIRONMENTS

We compared inbreeding depression in hermaphroditic Schiedea lydgatei and its gynodioecious sister species, S. salicaria, to infer the level of inbreeding depression in their common ancestor. With measurements of selfing rates, this information can be used to assess the importance of inbreeding depression in the evolution of breeding systems in S. lydgatei and S. salicaria. Morphological and physiological characters related to fitness were compared for inbred and outcrossed S. lydgatei in high- and low-fertilizer environments in the greenhouse. Seed mass, number of seeds per capsule, germination, survival, biomass, number of flowers, and age at first flowering were compared for inbred versus outcrossed progeny. We also measured inbreeding depression in maximal rates of photosynthetic carbon assimilation and stomatal conductance to water vapor, traits that affect fitness through their influence on plant carbon balance and water-use efficiency (ratio of carbon gain to water loss). All traits except number of seeds per capsule in parents and survival showed inbreeding depression, with the magnitude depending on family and environment. High inbreeding depression is likely in the ancestor of S. lydgatei and S. salicaria, indicating that, with sufficiently high selfing rates, females could spread in populations. Hermaphroditism in S. lydgatei is probably favored by low selfing rates. In contrast, the evolution of gynodioecy in S. salicaria apparently has been favored by relatively high selfing rates in combination with high inbreeding depression.