Under natural and greenhouse conditions we found a significant reduction in the physiological and biochemical constituents in leaves of five disease types when compared to healthy ones. The growth characteristics such as height, dry mass, photosynthetic and transpiration rates, stomatal conductance, and water use efficiency were reduced significantly more in susceptible cv. TRI-2024 than in tolerant cv. TRI-2025. Also contents of total sugars, nitrogen, amino acids, proteins, polyphenols, and catechin were reduced in diseased plant leaves. However, the reduction was more prominent in susceptible than tolerant cultivar. Canker size and barker moisture content were larger in the susceptible cultivar than in the tolerant cultivar. and P. Ponmurugan, U. I. Baby, R. Rajkumar.
This study was conducted to assess whether silicon (Si) supply can alleviate the harmful effects of severe salinity in barley (Hordeum vulgare). Plants were grown on non-saline (0 mM NaCl) or saline (200 mM NaCl) nutrient media supplemented or not with 0.5 mM Si. Salinity impacted plant morphology and induced sodium and chloride accumulation within plant tissues. It significantly affected almost all measured parameters. Interestingly, Si supply alleviated salt stress effects on plant morphology, growth (up to +59%), water status (up to +74%), membrane integrity (up to +35%), pigment contents (up to +121%), and the activity of the two photosystems (PSI and PSII) by improving their yields, and by reducing their energy dissipation. Si beneficial effect was more pronounced on PSI as compared to PSII. As a whole, data inferred from the present study further confirmed that silicon application is an effective approach to cope with salinity.
We analysed plant growth, ion accumulation, leaf water relations, and gas exchange of Avicennia germinans (L.) L. subjected to a long-term, controlled salinity gradient from 0 to 55 ‰. Growth and leaf area were affected by salinity higher than 10 ‰. As salinity increased, the predawn leaf water potential (Ψw) and leaf osmotic potential (Ψs) decreased. Leaf Ψw was at least -0.32 MPa lower than the Ψw of solution. Na+ and K+ ions explained about 78 % of decrease in Ψs. K+ tissue water concentration decreased by more than 60 % in all salinity treatments as compared with those grown at 0 ‰. Inversely, Na+ concentration in tissue water increased with nutrient solution salinity. The maximum net photosynthetic rate
(PN) and stomatal conductance (gs) decreased by 68 and 82 %, respectively, as salinity increased from 0 to 55 ‰; the intercellular CO2 concentration (Ci) followed the same trend. The PN as a function of Ci showed that both the initial linear slope and upper plateau of the PN vs. Ci curve were markedly affected by high salinity (40 and 55 ‰). and N. Suárez, E. Medina.
The combined effects of water stress (WS) and low irradiance (LI) on growth, photosynthesis, osmotic adjustment, and lipid peroxidation were studied in dragon spruce (Picea asperata Mast.) seedlings grown under two water treatments (well watered, 100 % of field capacity, and water stressed, 30 % of field capacity) and two irradiances (HI, 100 % of full sunlight and LI, 15 % of full sunlight). WS reduced growth, chlorophyll (Chl) a and b contents, net photosynthetic rate, transpiration rate, stomatal conductance, and effective quantum yield of photosystem 2 (Y) but increased free proline and malondialdehyde contents. LI increased Chl contents and decreased Y, photochemical quenching (qP), and non-photochemical quenching (qN) under both water treatments. Hence the seedlings in the understory were more sensitive to drought than to LI. and Y. Yang ... [et al.].
The review sums up research conducted at CIAT within a multidiscipline effort revolving around a strategy for developing improved technologies to increase and sustain cassava productivity, as well as conserving natural resources in the various eco-edaphic zones where the crop is grown, with emphasis on stressful environments. Field research has elucidated several physiological plant mechanisms underlying potentially high productivity under favourable hot-humid environments in the tropics. Most notable is cassava inherent high capacity to assimilate carbon in near optimum environments that correlates with both biological productivity and root yield across a wide range of germplasm grown in diverse environments. Cassava leaves possess elevated activities of the C4 phosphoenolpyruvate carboxylase (PEPC) that also correlate with leaf net photosynthetic rate (PN) in field-grown plants, indicating the importance of selection for high PN. Under certain conditions such leaves exhibit an interesting photosynthetic C3-C4 intermediate behaviour which may have important implications in future selection efforts. In addition to leaf PN, yield is correlated with seasonal mean leaf area index (i.e. leaf area duration, LAD). Under prolonged water shortages in seasonally dry and semiarid zones, the crop, once established, tolerates stress and produces reasonably well compared to other food crops (e.g. in semiarid environments with less than 700 mm of annual rain, improved cultivars can yield over 3 t ha-1 oven-dried storage roots). The underlying mechanisms for such tolerance include stomatal sensitivity to atmospheric and edaphic water deficits, coupled with deep rooting capacities that prevent severe leaf dehydration, i.e. stress avoidance mechanisms, and reduced leaf canopy with reasonable photosynthesis over the leaf life span. Another stress-mitigating plant trait is the capacity to recover from stress, once water is available, by forming new leaves with even higher PN, compared to those in nonstressed crops. Under extended stress, reductions are larger in shoot biomass than in storage root, resulting in higher harvest indices. Cassava conserves water by slowly depleting available water from deep soil layers, leading to higher seasonal crop water-use and nutrient-use efficiencies. In dry environments LAD and resistance to pests and diseases are critical for sustainable yields. In semiarid zones the crop survives but requires a second wet cycle to achieve high yields and high dry matter contents in storage roots. Selection and breeding for early bulking and for medium/short-stemmed cultivars is advantageous under semiarid conditions. When grown in cooler zones such and as in tropical high altitudes and in low-land sub-tropics, leaf PN is greatly reduced and growth is slower. Thus, the crop requires longer period for a reasonable productivity. There is a need to select and breed for more cold-tolerant genotypes. Selection of parental materials for tolerance to water stress and infertile soils has resulted in breeding improved germplasm adapted to both favourable and stressful environments.
Increasing human and industrial activities lead to heavy metal pollution. Heavy metal chromium (Cr) is considered to be a serious environmental contaminant for the biota. Phytotoxic effects of Cr were studied in wheat plants. Growth parameters were largely inhibited as a result of disturbances in the plant cell metabolism in response to Cr toxicity. Chromium toxicity led to decline in a number of active reaction centres of PSII, rate of electron transport, and change in PSII heterogeneity. Chromium did not cause any change in heterogeneity of the reducing side. A significant change in antenna size heterogeneity of PSII occurred in response to Cr toxicity. Chromium seems to have extensive effects on the light harvesting complex of PSII., S. Mathur, H. M. Kalaji, A. Jajoo., and Obsahuje seznam literatury
Life history traits of the vulnerable Iberian loach Cobitis calderoni were studied in the River Lozoya, a regulated river in Central Spain. A total of 163 specimens were collected on five occasions, from April to December 1990. In general C. calderoni grew isometrically and a length-frequency analysis showed 4–5 age classes. Parameters fitted to the von Bertalanffy growth model showed variation in growth rates between the sexes. The gonadosomatic index for both sexes were similar and varied among months, with the highest values in April, just before the onset of the spawning season in Spring.
In the internal French Alps, subalpine grasslands become dominated by the tussock grass, Festuca paniculata, when mowing ceases. Does litter or living plants affect seedling recruitment in these subalpine communities, and does this vary between mown and unmown grasslands? Can the vegetation patterns observed in the field be related to the effects of F. paniculata? These hypotheses were tested using both a field and pot experiment. Seedlings of Bromus erectus, a subordinate species in these grasslands, were used as phytometers in both experiments. At both mown and unmown subalpine grassland sites in the French Alps, a removal experiment was established. This field experiment included removal of litter and living vegetation in order to differentiate their respective effect on seedling establishment. Vegetation and litter had contrasting effects. Vegetation affected the recruitment success of B. erectus by limiting seedling growth at the mown site and survival at the unmown site. Litter modified recruitment only at the unmown site, where it increased survival but limited growth. Survival and growth of seedlings responded to different environmental factors. Survival was determinedmore by soilmoisture, while growth probably dependedmore on light availability.Where there is a thick litter layer, as is the case in unmown subalpine grasslands, the competitive effect of vegetation can be counterbalanced by an increase in soil moisture due to the litter reducing rate of evaporation of water. The effect on seedlings of the presence of Festuca paniculata, the dominant species at these sites, was also quantified using a pot experiment, including a cutting treatment. This experiment showed that the competitive effect of the vegetation could be largely explained by the inhibitory effect on growth of the dominant species, F. paniculata. This study provides a better understanding of the processes that result in conservative plants, such as F. paniculata, becoming dominant in these subalpine environments upon cessation of traditional management practices.
Current research on the effect of increased UV-B radiation on crop production has been limited to exposing plants to improbable UV-B dose or growth condition. The objective of this study was to test the effects of short-term modulated increased UV-B radiation on maize (Zea mays L.) growth, grain yield, and quality under field conditions for three years. A modulated irradiance system was used to maintain UV-B radiation at 30% above the ambient level and was applied daily between the elongation and silking stages of maize. The result indicated that increased UV-B radiation adversely affected maize growth and yield, especially on plant height when UV-B was enhanced at the elongation stage and on yield when UV-B was enhanced near the silking stage. Yield reduction that induced by enhanced UV-B radiation was associated with reductions in number of kernels per row and kernel mass. Protein content of grains was increased with enhanced UV-B radiation, but oil and starch contents were not affected. This study confirmed the sensitivity of maize to increased UV-B radiation under the field condition, and contributed to understand the full negative and positive effects of increased UV-B radiation on crop production., L. N. Yin, S. W. Wang., and Obsahuje bibliografii
Little is known of the life history of Cobitiscf. satunini, a loach species native to the Caucasus and southern Caspian Basin. Life history characteristics of this species were examined in 568 specimens collected from the Siahroud stream (northern Iran) between February and June 2010. The specimens ranged in size from 27 to 103 mm total length and weighed from 0.13 to 8.93 g total weight. The overall sex ratio was unbalanced as females dominated, with 342 females and 226 males being caught (sex ratio 1.5 : 1). Length-weight relationships implied that growth was positively allometric for both sexes. The von Bertalanffy growth function was estimated to be Lt = 94.95 (1 – e– 0.49 (t + 0.34)) for males and Lt = 121.65 (1 – e–0.39(t + 0.43)) for females. Egg diameter ranged from 0.44 to 1.02 mm, with a mean value of 0.77 mm. Absolute fecundity varied from 212 to 4666 eggs. Fecundity relative to total weight fluctuated from 383 to 268 eggs g–1. These growth and reproduction traits may be interpreted as species life history capacity and/or adaptation to environmental conditions caused by the southern Caspian climate.