The number of larval moults, larval head capsule width and pupal weight were investigated in both direct-developing and diapausing individuals of a South-West European population of Coenonympha pamphilus. The frequency distributions of head widths of successive larval instars overlapped, partly due to variation in the number of larval moults. The larvae that entered diapause went through five instars, instead of the four reported from this species. The evidence indicates that the five instar developmental pathway represents a plastic response rather than an example of compensatory growth. This alternative growth pattern was expressed in response to short photoperiods in parallel with, or as a consequence of, larval diapause. On average, the larvae with five instars had larger heads than their normal siblings. This resulted in comparatively heavier male pupae, while the opposite trend occurred in females. It is concluded that the variation in the number of larval instars is a plastic response to diapause when temperatures remain mild and that it might have an adaptive value in areas with mild winter climates. The sexually dimorphic expression in the larval growth patterns, in terms of pupal weight, may well imply different patterns of allocation of larval resources to adult structures, although sex-dependent differences in investment into purely larval structures cannot be discounted.
Life-history parameters of Barbus peloponnesius and Barbus cyclolepis were studied in two streams in Macedonia, Greece. In B. peloponnesius age ranged from 0+ to 4+ in males and 0+ to 9+ in females, while in B. cyclolepis from 0+ to 5+ in males and 0+ to 9+ in females. In both species, after the first year of life, females exhibited longer mean lengths at age and greater maximum length than the males, while between species B. cyclolepis showed greater mean lengths at age and greater maximum length than B. peloponnesius. Total mortality rates were higher in the males of each species than in females. Significant difference in the sex ratio was found only for B. cyclolepis and this species population was male dominated. Gonad maturation began at the age of 1+ in males and 3+ in females of both species. Both species exhibited a protracted multi-spawning season, which started at the end of March-beginning of April and lasted until mid July. Despite differences in growth and body size, the two species are characterized by similar life-history styles: (1) similar age structure, (2) early maturation and same age at maturity, (3) males have a shorter life span, higher rate of mortality, decreased growth and smaller body size and mature earlier than the females and (4) elongated multi-spawning season, which shows a high investment in reproduction. The life-history style of the two stocks seems to be in concordance with the environmental conditions of their habitats, which are typical of the fluctuating Mediterranean streams.
a1_The modern concept of causality of diseases emphasizes the study of natural defense functions of the organism and possibilities of influencing them, which will lead to effective prevention of these diseases. A great deal of information has been obtained on the system growth hormone (GH)/insulin-like growth factor (IGF)-I, which is of quite fundamental importance for the integrity of the organism. A dysbalance of the system may be the cause of diseases of the neonatal period, as well as diseases associated with aging. In old age, the synthesis of the crucial peptide system, IGF-I, declines as well as the sensitivity of tissues to this hormone. At the same time the changes in the expression of IGF-binding proteins (IGFBP) occur. Systemic growth factors are present in measurable concentrations in the circulation, they are, however, taken up or synthesized by some tissues, where they act as local cellular regulators. IGF-I is produced by many tissues, including bones under the control of estrogens, growth hormone and the parathyroid hormone. A decline of bone IGF-I in the cortical portion of bones is one of the many mechanisms leading to the development of involutional osteoporosis. Correlation studies, which have provided evidence of a relationship between the IGF system and the building of peak bone mass and its subsequent loss contributed to the understanding of the pathogenesis of this disease. It may be foreseen that the results of intervention studies focused on the effects of the recombinant IGF-I will also influence therapeutic and preventive approaches. Modern antiresorption pharmacotherapy stabilizes or enhances bone density and reduces the risk of fractures. The addition of effective anabolics might increase the effectiveness of treatment by shifting the remodeling equilibrium in favor of formative processes., a2_Because both recombinant GH and IGF-I have certain therapeutic limitations, it is considered to utilize substances which either stimulate endogenous IGF-I production directly in the bone or modulate synthesis and distribution of binding proteins for the peptide. Further new findings related to physiology and pathophysiology of this peptide will contribute to designing new strategies in the prevention of osteoporosis and other serious diseases of old age, such as diabetes, neoplasias or cardiovascular diseases., I. Žofková., and Obsahuje bibliografii
Light is a limiting factor in plant establishment and growth in the understory of forests. In this paper, we assessed acclimation capacity of Siparuna guianensis, an early secondary successional species. We used seedlings and saplings in three regeneration areas with different irradiance regimes to determine the traits that confer photoplasticity. We examined whether these traits differ at different developmental stages. Anatomical characteristics, photochemical efficiency, photosynthetic capacity, and growth were analyzed. Multivariate component analysis revealed the formation of six clusters: three for seedlings (one for each regeneration area) and three for saplings (following the same pattern of seedlings, considering the area). Increased irradiance favored photosynthetic performance, independently of the developmental stage. The same trend was observed for most data on chlorophyll (Chl) a fluorescence and the ratios of net photosynthetic rate/intercellular CO2 concentration (PN/Ci) and PN/PPFD. No parameter indicated photoinhibition stress. The CO2- and light-response curve data indicated that seedlings were already acclimated to tolerate variation in irradiance. Anatomical adaptations, such as thickness of leaf blade and of adaxial cuticle, were observed in individuals growing in areas with higher irradiation. Thinning of spongy parenchyma and higher investment into a plant height were observed in seedlings, possibly due to the vertical stratification of CO2 and light in the understory; because light is a more limiting resource than CO2 in the lower stratum of the forest. Photoplasticity in S. guianensis is associated with a set of morphological, anatomical, photochemical, and biochemical traits, whereas biochemical performance is best acclimated to variation in irradiance. These traits differed in seedlings and saplings but they were modulated mainly by irradiance in both developmental stages., T. O. Vieira, M. S. O. Degli-Esposti, G. M. Souza, G. R. Rabelo, M. Da Cunha, A. P. Vitória., and Obsahuje bibliografii
The diurnal variation of net photosynthetic (PN) and transpiration (E) rates in soybean [Glycine max (L.) Merr. cv. Fukuyutaka] plants grown under 100, 50, or 25 % of full sun irradiance (I100, I50, I25 plants) were compared. In the morning, activities of the plants were measured at irradiances under which they grew. However, during the afternoon, all the plants were tested under full irradiance. The lower the growth irradiance, the lower PN, E, and mesophyll conductance values were found. Stomatal conductance was considerably lower in I25 plants only. Both the increase in specific leaf area (SLA) and the decrease in nitrogen content per leaf area unit contributed to the PN reduction of soybean plants grown under low irradiances. Though E of the plants grown under different irradiances differed less markedly than PN, the water use efficiency declined from I100 to I25. and Y. Koesmaryono ... [et al.].
We found differences between true leaves (TL) and phyllodes (Ph) during ontogeny of Acacia mangium plants as reflected in chlorophyll (Chl) and carotenoid contents, gas exchange, Chl fluorescence, and growth. The production of TL enhanced the relative growth rate of the A. mangium seedlings, allowing the plants to accumulate enough dry biomass for later growth, while the production of thicker Ph in the later growth stage of A. mangium could help plants to cope with higher irradiance in their natural growth conditions. and H. Yu, J.-T. Li.
The dynamics of the terrestrial ecosystems depend on interactions between a number of biogeochemical cycles (i.e. carbon, nutrient, and hydrological cycles) that may be modified by human actions. Conversely, terrestrial ecosystems are important components of these cycles that create the sources and sinks of important greenhouse gases (e.g. carbon dioxide, methane, nitrous oxide). Especially, carbon is exchanged naturally among these ecosystems and the atmosphere through photosynthesis, respiration, decomposition, and combustion processes. Continuous increase of atmospheric carbon dioxide (CO2) concentration has led to extensive research over the last two decades, during which more then 1 400 scientific papers describing impacts of elevated [CO2] (EC) on photosynthesis have been published. However, the degree of response is very variable, depending on species, growing conditions, mineral nutrition, and duration of CO2 enrichment. In this review, I have summarised the major physiological responses of plants, in particular of trees, to EC including molecular and primary, especially photosynthetic, physiological responses. Likewise, secondary (photosynthate translocation and plant water status) and tertiary whole plant responses including also plant to plant competition are shown.
In order to evaluate the combined effects of simulated acid rain (SAR) and salinity on the physiological responses of macroalgae, Ulva prolifera was cultured under three salinity treatments (5, 10,
25‰) and at different pH, i.e., at pH 4.4 (C), pH 4.4(F), where the pH of the culture increased from 4.4 to approximately 7.8 during the cultivation period, or in absence of SAR at pH 8.2(C), at 100 μmol(photon) m-2 s-1 and 20°C. Compared to 25‰ salinity, Relative growth rate (RGR) of U. prolifera was enhanced by 10‰ salinity, but decreased by 5‰ salinity. No significant differences in RGR were observed between the pH 8.2(C) and pH 4.4(F) treatments, but the chlorophyll a content was reduced by SAR. Negative effects of SAR on the photosynthesis were observed, especially under low salinity treatments. Based on the results, we suggested that the U. prolifera showed a tolerance to a wide range of salinity in contrast to the low pH induced by acid rain., Y. H. Li, D. Wang, X. T. Xu, X. X. Gao, X. Sun, N. J. Xu., and Obsahuje použitou literaturu
We quantified the physiological responses of black willow to four soil moisture regimes: no flooding (control, C), continuous flooding (CF), periodic flooding (PF), and periodic drought (PD). Stomatal limitation was one of the factors that led to the reduced photosynthetic capacity in CF cuttings. Under PD, stomatal closure, decreased leaf chlorophyll content, and increased dark fluorescence yield contributed to photosynthetic decline. CF cuttings accumulated the lowest shoot biomass while the final height and root growth were most adversely affected by PD. PF cuttings tended to allocate more photoassimilates to root growth than to shoots. and S. Li ... [et al.].
Since 2002, Silver buffaloberry (Shepherdia argentea) has been introduced from North America in order to improve the fragile ecological environment in western China. To elucidate the
salt-resistance mechanism of S. argentea, we conducted a test with two-year-old seedlings subjected to 0, 200, 400, and 600 mM NaCl solutions for 30 d. The results showed that significant salt-induced suppression of plant fresh mass (FM) and stem height of S. argentea seedlings occurred only at the highest salinity level (600 mM). Leaf number, plant dry mass (DM), and chlorophyll (Chl) content declined markedly at both 400 and 600 mM. Leaf area (LA) and leaf water potential (Ψw) continuously declined with the increase of salinity. There was also a progressive and evident decrease in net photosynthetic rate (PN), transpiration rate (E), and stomatal conductance (gs) with the increase of salinity and time. The correlation analysis indicated that PN was positively correlated with gs at all salinity levels while correlated with intercellular CO2 concentration (Ci) only at moderate salinity levels (<600 mM). Based on the initial slope of the PN/Ci curves, the estimated carboxylation efficiency (CE) was strongly inhibited at 600 mM. We confirm that S. argentea is highly tolerant to salinity. Moreover, our results show that at moderate salinity levels, salt-induced inhibition of photosynthesis is mainly attributed to the stomatal efficient closure predetermined by a low water potential in leaves; while at the high salinity levels, the inhibition is mainly due to the suppression of chloroplast capacity to fix CO2 caused by the serious decline in both CE and Chl contents. and J. Qin ... [et al.].