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Eucalyptus species are strong source of isoprenoid emission. The objective of the present study was to estimate isoprenoid emissions from Eucalyptus grandis forest crops in the Entre Rios province in the Mesopotamia region of Argentina. The emission rates of isoprene and monoterpenes were measured on individual leaves under; controlled environmental conditions. At 30°C and with a PPFD of 1000 μM m-2 s-1 the emission rate of isoprene emission was 12.5 ± 1.9 nM m-2 s-1 and monoterpenes 15.1 ± 3.1 nM m-2 s-1. Emission was significantly affected by leaf position and decreased significantly from East to West. The most abundant compound emitted was limonene, accounting for between 50 and 68% of the total monoterpene emission. The time course of the isoprene emission course showed its strong dependence on light. On sunny days 42% of the isoprene emission comes from top of the canopy and only 2% from bottom of the canopy. But on overcast days, the relative contribution of diffuse radiation may be larger and can exceed the contribution of direct radiation. A model procedure in a Geographic Information System was implemented to estimate isoprene emissions at a regional scale. A forest inventory, data from a meteorological station and leaf area indices derived from satellite data served as inputs for the model. For the Entre Rios province (78781 km²), the isoprene emission totals up to 39.5 t d-1 on a clear summer day. The methodology applied to estimate isoprenoid emissions on a regional scale contributes to the understanding of carbon exchange between biosphere and atmosphere. [ABSTRACT FROM AUTHOR]

We assessed the response to drought in Corymbia citriodora, a fast growing wood-crop with high levels of water-loss, and Ziziphus nummularia, a tree species that occurs in arid areas of Asia and a potential alternative wood-crop plantation species in drought-prone regions. Z. nummularia was able to sustain higher levels of stomatal conductance at lower levels of soil water availability than C. citriodora. The leaves of Z. nummularia also contained higher levels of the antioxidant peroxidase, offering enhanced protection from drought induced oxidative stress. The carbon isotopic and nitrogen concentration of C. citriodora foliage was strongly affected by decreasing soil water availability, but a compositional effect was only apparent in Z. nummularia leaves at the lowest level of soil water. The higher leaf levels of stomatal conductance and nitrogen are indicative of relatively high assimilation rates in Z. nummularia, suggesting that this species is capable of fully exploiting brief periods where conditions are limited for growth. These attributes, in combination with its inherent tolerance to drought, may make Z. nummularia a suitable wood crop species for rain-fed plantations in drought-prone areas. © 2015 Friends Science Publishers [ABSTRACT FROM AUTHOR]

Decreased water levels cause severe reduction in growth and yield of plants. Generally the plant growth is inhibited under water stress due to the high concentration of ethylene in the rhizosphere. Plant growth promoting rhizobacteria (PGPR) inhabiting the rhizosphere capable of producing 1-aminocyclopropane-1-carboxylate deaminase (ACCd) enzyme can also reduce the concentration of ethylene in plant by breaking down Acc, the immediate precursor of ethylene. Such PGPR were isolated from different parts of the province of Punjab and Khyber Pakhtunkhwa and screened for their ability to promote growth of velvet bean in axenic conditions. The results showed that some rhizobacterial strains significantly improved the growth of roots and shoots in normal and water stress condition. A significant increase was observed in root length (32%), shoot length (110%), root dry weight (50%) and shoot dry weight (60%) in response to inoculation compared to an uninoculated control. Four strains showed very encouraging results in promoting the growth of velvet bean. The ability of selected rhizobacteria to reduce the concentration of ethylene was confirmed by performing classical triple response bioassay in etiolated pea seedlings. The results of this study illustrate that ACCd active PGPR can be used for improving plant growth and yield of velvet bean under limited availability of water. © 2015 Friends Science Publishers [ABSTRACT FROM AUTHOR]

Investigations about phenotypic plasticity and adaptive traits of species facing rapidly changing stressful conditions are particularly relevant in context of rapid climate change. Morphological and physiological traits of Quercus aquifolioides plants growing at 2600 m and 3500 m above sea level (in the vicinity of the tree line) were studied. Leaf mesophyll conductance (gm) and stomatal conductance (gs) decreased, whereas carbon isotope composition (δ13C), nitrogen concentration and dark respiration increased with elevation. The specific leaf area (SLA) did not change, whereas photosynthetic capacity was dramatically inhibited at higher elevation. Differences in decline of photosynthesis (∼64%) and gm (∼80%) at elevations were reflected by similar chloroplast (Pc) to atmospheric (Pa) CO2 partial pressure ratio between the two populations. Therefore, δ13C changes were not associated to either SLA or Pc/Pa, d13C furnished an estimation of long-term Pc/Pa and, in turn, of long-term water use efficiency. Air temperature, which decreased consistently with altitude, significantly affected the long-term Pc/Pa. Plausibly, low temperature is the main determinant affecting δ13C at high altitude. In conclusion, phenotypic plasticity enabled Q. aquifolioides to maintain a positive carbon balance in response to dramatic environmental changes. [ABSTRACT FROM AUTHOR]