Secondary Pollen Presentation in Angiosperms and Its Biological Significance

1993 ◽  
Vol 41 (5) ◽  
pp. 417 ◽  
Author(s):  
GJ Howell ◽  
AT Slater ◽  
RB Knox
Keyword(s):  
Close Association ◽  
Biological Significance ◽  
Selective Advantage ◽  
Floral Organ ◽  
Pollinator Behaviour ◽  
Secondary Pollen Presentation ◽  
Male Function ◽  
Increased Risk ◽  
Pollen Presentation ◽  
Male Phase

Secondary pollen presentation is the developmental relocation of pollen from the anthers onto another floral organ which then functions as the pollen presenting organ for pollination. Nine different types have been identified in sixteen angiosperm families according to which organ is used for presentation, whether the pollen is exposed or concealed within a structure and how pollen is loaded onto the presenting surface: (1) Enveloping bloom presenters (Araceae); (2) Perianth presenters with exposed pollen presentation (Epacridaceae); (3) Androecial presenters (Santalaceae); (4) Terminal stylar presenters with passive pollen placement and concealed stigmas (Rubiaceae and Proteaceae); (5) Terminal stylar presenters with passive pollen placement and sub-terminal stigmas (Marantaceae and Polygalaceae); (6) Terminal stylar presenters with active pollen placement (Asteraceae, Calyceraceae and Lobeliaceae); (7) Sub-terminal stylar presenters (Campanulaceae, Cannaceae, Fabaceae and Myrtaceae); (8) Exposed stigmatic presenters (Rubiaceae); (9) Indusial stigmatic presenters (Goodeniaceae and Brunoniaceae). Secondary pollen presentation occurs in three monocotyledon and thirteen dicotyledon families. The presentation types appear to have been independently derived indicating that secondary pollen presentation is a character with a selective advantage. In all but the enveloping bloom type of secondary pollen presentation, developmental relocation of pollen requires simultaneous, introrse anther dehiscence and a close association of the presenting organ to the anthers prior to anthesis. The various secondary pollen presentation systems may be modified to promote xenogamy or autogamy and this can even change during anthesis. Most plants which have secondary pollen presentation, display reduced herkogamy within the flower to facilitate pollination. Increased risk of self-pollination due to this may be overcome through dichogamy, herkogamy within inflorescences, dry stigmas, self-incompatibility systems and passive or active control over pollinator behaviour. Enhanced male function of the flowers of secondary pollen presenting plants is also evident through extension of the male phase by the protection, controlled release and precise placement and receipt of pollen. Plants displaying secondary pollen presentation are almost always protandrous.

Could Antioxidant Supplementation Delay Progression of Cardiovascular Disease in End-Stage Renal Disease Patients?

2020 ◽  
Vol 19 (1) ◽  
pp. 41-54 ◽  
Author(s):  
Stefanos Roumeliotis ◽  
Athanasios Roumeliotis ◽  
Xenia Gorny ◽  
Peter R. Mertens
Keyword(s):  
Oxidative Stress ◽  
Renal Disease ◽  
End Stage Renal Disease ◽  
Close Association ◽  
Omega 3 ◽  
Endstage Renal Disease ◽  
Increased Risk ◽  
Underlying Mechanisms ◽  
Stage Renal Disease ◽  
End Stage

In end-stage renal disease patients, the leading causes of mortality are of cardiovascular (CV) origin. The underlying mechanisms are complex, given that sudden heart failure is more common than acute myocardial infarction. A contributing role of oxidative stress is postulated, which is increased even at early stages of chronic kidney disease, is gradually augmented in parallel to progression to endstage renal disease and is further accelerated by renal replacement therapy. Oxidative stress ensues when there is an imbalance between reactive pro-oxidants and physiologically occurring electron donating antioxidant defence systems. During the last decade, a close association of oxidative stress with accelerated atherosclerosis and increased risk for CV and all-cause mortality has been established. Lipid peroxidation has been identified as a trigger for endothelial dysfunction, the first step towards atherogenesis. In order to counteract the deleterious effects of free radicals and thereby ameliorate, or delay, CV disease, exogenous administration of antioxidants has been proposed. Here, we attempt to summarize existing data from studies that test antioxidants for CV protection, such as vitamins E and C, statins, omega-3 fatty acids and N-acetylcysteine.

Diabetes and Heart Failure: Is it Hyperglycemia or Hyperinsulinemia?

2020 ◽  
Vol 18 (2) ◽  
pp. 148-157 ◽  
Author(s):  
Triantafyllos Didangelos ◽  
Konstantinos Kantartzis
Keyword(s):  
Heart Failure ◽  
Insulin Treatment ◽  
Close Association ◽  
Adverse Outcomes ◽  
Negative Effects ◽  
Beneficial Effects ◽  
Appropriate Treatment ◽  
Increased Risk ◽  
Treatment Of Diabetes

The cardiac effects of exogenously administered insulin for the treatment of diabetes (DM) have recently attracted much attention. In particular, it has been questioned whether insulin is the appropriate treatment for patients with type 2 diabetes mellitus and heart failure. While several old and some new studies suggested that insulin treatment has beneficial effects on the heart, recent observational studies indicate associations of insulin treatment with an increased risk of developing or worsening of pre-existing heart failure and higher mortality rates. However, there is actually little evidence that the associations of insulin administration with any adverse outcomes are causal. On the other hand, insulin clearly causes weight gain and may also cause serious episodes of hypoglycemia. Moreover, excess of insulin (hyperinsulinemia), as often seen with the use of injected insulin, seems to predispose to inflammation, hypertension, dyslipidemia, atherosclerosis, heart failure, and arrhythmias. Nevertheless, it should be stressed that most of the data concerning the effects of insulin on cardiac function derive from in vitro studies with isolated animal hearts. Therefore, the relevance of the findings of such studies for humans should be considered with caution. In the present review, we summarize the existing data about the potential positive and negative effects of insulin on the heart and attempt to answer the question whether any adverse effects of insulin or the consequences of hyperglycemia are more important and may provide a better explanation of the close association of DM with heart failure.

Self-interference is reduced in a secondary pollen presentation species, Duperrea pavettifolia (Rubiaceae)

Flora ◽  
2012 ◽  
Vol 207 (12) ◽  
pp. 895-902 ◽  
Author(s):  
Hua Lin ◽  
Xuli Fan ◽  
Xiang Zhou ◽  
Jiangyun Gao
Keyword(s):  
Secondary Pollen Presentation ◽  
Pollen Presentation

Stamen Movement and its Biological Significance in Compositae Plants

2014 ◽  
Vol 1073-1076 ◽  
pp. 1079-1085
Author(s):  
Jia Shi Zeng ◽  
Dong Xu Wang ◽  
Yang Liu ◽  
Xiao Ping Lu
Keyword(s):  
Cell Structure ◽  
Biological Significance ◽  
Floral Organ ◽  
Physical Movement ◽  
Microscopic Measurement

There is a unique inflorescence composition and stamen structure in Compositae. Stamen structure, filament movement and its mechanism was analyzed and discussed, with cosmos and small sunflowers as experimental materials, by using morphological anatomy, microscopic measurement, tabletting observation. The results showed that: (1) There was a certain regularity in the opening of tubular floral organ in capitulum, of which their movements were initiated from outside to inside. (2) The mainly cause of stamen movement in Compositae came from the changes filaments length. (3) Stamen movement was not a simple physical movement-with filaments shortening, cell structure also has changed. (4) The filament movement in Compositae is not only beneficial to itself fully stretching, but also reduces the interference during pollen spreading.

scholarly journals Is there a role for inherited TR βmutation in human carcinogenesis?

2012 ◽  
Vol 56 (1) ◽  
pp. 67-71 ◽  
Author(s):  
Letícia Schwerz Weinert ◽  
Lucieli Ceolin ◽  
Mírian Romitti ◽  
Eduardo Guimarães Camargo ◽  
Ana Luiza Maia
Keyword(s):  
Thyroid Hormone ◽  
Potential Role ◽  
Thyroid Hormone Receptor ◽  
Close Association ◽  
Common Finding ◽  
Illustrative Case ◽  
Increased Risk ◽  
Exon 9

Resistance to thyroid hormone (RTH) is a rare autosomal dominant inherited disorder characterized by end-organ reduced sensitivity to thyroid hormone. This syndrome is caused by mutations of the thyroid hormone receptor (TR) β gene, and its clinical presentation is quite variable. Goiter is reported to be the most common finding. A close association of TRβ mutations with human cancers has become apparent, but the role of TRβ mutants in the carcinogenesis is still undefined. Moreover, higher TSH levels, described in RTH syndrome, are correlated with increased risk of thyroid malignancy, whereas TSH receptor stimulation is likely to be involved in tumor progression. We report here an illustrative case of a 29 year-old patient with RTH caused by a mutation in exon 9 (A317T) of TRβ gene, who presented multicentric papillary thyroid cancer. We review the literature on this uncommon feature, and discuss the potential role of this mutation on human tumorigenesis, as well as the challenges in patient follow-up.

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