Climbing into the Big Picture Scaling Physiological Processes: Leaf to Globe James R. Ehleringer Christopher B. Field

BioScience ◽  
1994 ◽  
Vol 44 (3) ◽  
pp. 188-189
Author(s):  
R. K. Monson
2021 ◽  
Vol 22 (7) ◽  
pp. 3428
Author(s):  
Daniel Nedvěd ◽  
Petr Hošek ◽  
Petr Klíma ◽  
Klára Hoyerová

Cytokinins are a class of phytohormones, signalling molecules specific to plants. They act as regulators of diverse physiological processes in complex signalling pathways. It is necessary for plants to continuously regulate cytokinin distribution among different organs, tissues, cells, and compartments. Such regulatory mechanisms include cytokinin biosynthesis, metabolic conversions and degradation, as well as cytokinin membrane transport. In our review, we aim to provide a thorough picture of the latter. We begin by summarizing cytokinin structures and physicochemical properties. Then, we revise the elementary thermodynamic and kinetic aspects of cytokinin membrane transport. Next, we review which membrane-bound carrier proteins and protein families recognize cytokinins as their substrates. Namely, we discuss the families of “equilibrative nucleoside transporters” and “purine permeases”, which translocate diverse purine-related compounds, and proteins AtPUP14, AtABCG14, AtAZG1, and AtAZG2, which are specific to cytokinins. We also address long-distance cytokinin transport. Putting all these pieces together, we finally discuss cytokinin distribution as a net result of these processes, diverse in their physicochemical nature but acting together to promote plant fitness.


Author(s):  
James Cronshaw ◽  
Jamison E. Gilder

Adenosine triphosphatase (ATPase) activity has been shown to be associated with numerous physiological processes in both plants and animal cells. Biochemical studies have shown that in higher plants ATPase activity is high in cell wall preparations and is associated with the plasma membrane, nuclei, mitochondria, chloroplasts and lysosomes. However, there have been only a few ATPase localization studies of higher plants at the electron microscope level. Poux (1967) demonstrated ATPase activity associated with most cellular organelles in the protoderm cells of Cucumis roots. Hall (1971) has demonstrated ATPase activity in root tip cells of Zea mays. There was high surface activity largely associated with the plasma membrane and plasmodesmata. ATPase activity was also demonstrated in mitochondria, dictyosomes, endoplasmic reticulum and plastids.


Author(s):  
A. E. Hotchkiss ◽  
A. T. Hotchkiss ◽  
R. P. Apkarian

Multicellular green algae may be an ancestral form of the vascular plants. These algae exhibit cell wall structure, chlorophyll pigmentation, and physiological processes similar to those of higher plants. The presence of a vascular system which provides water, minerals, and nutrients to remote tissues in higher plants was believed unnecessary for the algae. Among the green algae, the Chaetophorales are complex highly branched forms that might require some means of nutrient transport. The Chaetophorales do possess apical meristematic groups of cells that have growth orientations suggestive of stem and root positions. Branches of Chaetophora incressata were examined by the scanning electron microscope (SEM) for ultrastructural evidence of pro-vascular transport.


2009 ◽  
Vol 14 (2) ◽  
pp. 109-119 ◽  
Author(s):  
Ulrich W. Ebner-Priemer ◽  
Timothy J. Trull

Convergent experimental data, autobiographical studies, and investigations on daily life have all demonstrated that gathering information retrospectively is a highly dubious methodology. Retrospection is subject to multiple systematic distortions (i.e., affective valence effect, mood congruent memory effect, duration neglect; peak end rule) as it is based on (often biased) storage and recollection of memories of the original experience or the behavior that are of interest. The method of choice to circumvent these biases is the use of electronic diaries to collect self-reported symptoms, behaviors, or physiological processes in real time. Different terms have been used for this kind of methodology: ambulatory assessment, ecological momentary assessment, experience sampling method, and real-time data capture. Even though the terms differ, they have in common the use of computer-assisted methodology to assess self-reported symptoms, behaviors, or physiological processes, while the participant undergoes normal daily activities. In this review we discuss the main features and advantages of ambulatory assessment regarding clinical psychology and psychiatry: (a) the use of realtime assessment to circumvent biased recollection, (b) assessment in real life to enhance generalizability, (c) repeated assessment to investigate within person processes, (d) multimodal assessment, including psychological, physiological and behavioral data, (e) the opportunity to assess and investigate context-specific relationships, and (f) the possibility of giving feedback in real time. Using prototypic examples from the literature of clinical psychology and psychiatry, we demonstrate that ambulatory assessment can answer specific research questions better than laboratory or questionnaire studies.


1995 ◽  
Vol 40 (9) ◽  
pp. 870-871
Author(s):  
Valerian J. Derlega
Keyword(s):  

2007 ◽  
Author(s):  
N. Kalezic ◽  
U. Aasa ◽  
M. Barnekow-Bergkvist ◽  
E. Lyskov

1986 ◽  
Vol 56 (01) ◽  
pp. 023-027 ◽  
Author(s):  
C J Jen ◽  
L V McIntire

SummaryWhether platelet microtubules are involved in clot retraction/ contraction has been controversial. To address this question we have simultaneously measured two clotting parameters, clot structural rigidity and isometric contractile force, using a rheological technique. For recalcified PRP clots these two parameters began rising together at about 15 min after CaCl2 addition. In the concentration range affecting microtubule organization in platelets, colchicine, vinca alkaloids and taxol demonstrated insignificant effects on both clotting parameters of a recalcified PRP clot. For PRP clots induced by adding small amounts of exogenous thrombin, the kinetic curves of clot rigidity were biphasic and without a lag time. The first phase corresponded to a platelet-independent network forming process, while the second phase corresponded to a platelet-dependent process. These PRP clots began generating contractile force at the onset of the second phase. For both rigidity and force parameters, only the second phase of clotting kinetics was retarded by microtubule affecting reagents. When PRP samples were clotted by adding a mixture of CaCl2 and thrombin, the second phase clotting was accelerated and became superimposed on the first phase. The inhibitory effects of micro tubule affecting reagents became less pronounced. Thrombin clotting of a two-component system (washed platelets/ purified fibrinogen) was also biphasic, with the second phase being microtubule-dependent. In conclusion, platelet microtubules are important in PRP clotted with low concentrations of thrombin, during which fibrin network formation precedes platelet-fibrin interactions. On the other hand they are unimportant if a PRP clot is induced by recalcification, during which the fibrin network is constructed in the presence of platelet-fibrin interactions. The latter is likely to be more analogous to physiological processes in vivo.


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