Selection of species and provenances for low-rainfall areas: physiological responses of Eucalyptus cloeziana and Eucalyptus argophloia to seasonal conditions in subtropical Queensland

Responses of stomatal conductance (g(s)) and net photosynthesis (A) to changes in soil water availability, photosynthetic photon flux density (Q), air temperature (1) and leaf-to-air vapour pressure deficit (D) were investigated in 4-year-old trees of a dry inland provenance of Eucalyptus argophloia Blakely, and two dry inland provenances (Coominglah and Hungry Hills) and a humid coastal provenance (Wolvi) of Eucalyptus cloeziana F. Muell. between April 2001 and April 2002 in southeast Queensland, Australia. There were minimal differences in A, g, and water relations variables among the coastal and inland provenances of E. cloeziana but large differences between E. argophloia and E. cloeziana. E. argophloia and to a lesser extent the Hungry Hills (inland) provenance of E. cloeziana maintained relatively higher pre-dawn water potential (psi(pd)) during the dry season suggesting possible access to water at depth. Simple phenomenological models of stomatal conductance as a function of Q, T and D explained 60% of variation in gs in E. cloeziana and more than 75% in E. argophloia, when seasonal effect was incorporated in the model. A Ball-Berry model for net photosynthesis explained between 70 and 80% of observed variation in A in both species. These results have implications in matching the dry and humid provenances of E. cloeziana and E. argophloia to suitable sites in subtropical environments. (C) 2004 Elsevier B.V. All rights reserved.

Effect after introducing Bacillus thuringiensis gene on nitrogen metabolism in cotton

Bacillus thuringiensis (Bt) transgenic cotton has shown changes of vegetative and reproductive growth characteristics. The objective of this study was to investigate the physiological change of nitrogen metabolism that related closely to the growth in Bt cotton cultivars. The study Was undertaken on two 131 transgenic cotton cultivars and their parents, one conventional (Xingyang822) and recurrent parent (Sumian No. 9), the other a hybrid (Kumian No. 1) and female parent (Yumian No. 1), during the 2001 and 2002 growing seasons at the Yangzhou University Farm, Yangzhou, China. In the 2001 study, The results indicated that the Bt cotton cultivars were higher than their parents in leaf total nitrogen, free amino acid and soluble protein content, greater in NR and GPT activity, and lower in protease activity, during peak square and boll developing period. The biggest increase of total nitrogen was at peak boll period, which increased by 36.01 and 18.96% for Kumian No. I and Xingyang822, respectively. There were similar results for free amino acid and soluble protein content. The results showed further in 2002 study that NR activity increased dramatically at peak square and early boll open period, the biggest increase at early boll open period, with Kumian No. I and Xingyan,822 being 87.5 and 61.4% higher than their parent, respectively, the biggest increase of GPT activity was at peak boll period, with Kumian No. I and Xingyang822 being 39.1 and 29.1% higher than their parent, respectively. However, protease activity of Bt cultivars reduced significantly before flowering and early boll open period, the biggest decrease was before flowering period, with Kumian No. I being more than 30%, Xingyang822 being 26.5% at peak square period. Moreover, the boll total nitrogen content reduced sharply. The results suggest that the Bt cotton cultivars have higher intensity of leaf nitrogen metabolism than their parent, especially during square and boll development period. It is disadvantage for square development and earlier boll maturity under high nitrogen condition. The cultural practice should aim at reducing leaf nitrogen metabolic strength and keep the balance of vegetative and reproductive growth. (C) 2003 Elsevier B.V. All rights reserved.

The effect of timing and severity of water deficit on growth, development, yield accumulation and nitrogen fixation of mungbean

Mungbean (Vigna radiata L.), as a dryland grain legume, is exposed to varying timing and severity of water deficit, which results in variability in grain yield, nitrogen accumulation and grain quality. In this field study, mungbean crops were exposed to varying timing and severity of water deficit in order to examine: (1) contribution of the second flush of pods to final grain yield with variable timing of relief from water deficit, (2) the sensitivity to water deficit of the accumulation of biomass and nitrogen (N) and its partitioning to grain, and (3) how the timing of water deficit affects the pattern of harvest index (HI) increase through pod filling. The results showed that the contribution of the second flush to final yield is highly variable (1-56%) and can be considerable, especially where mid-season stress is relieved at early pod filling. The capacity to produce a second flush of pods did not compensate fully for yield reduction due to water stress. Relief from mid-season stress also resulted in continued leaf production, N-2 fixation and vegetative biomass accumulation during pod filling. Despite the wide variation in the degree of change in vegetative biomass and N during pod filling, there were strong relationships between grain yield and net-above-ground biomass at maturity, and grain N and above-ground N at maturity. Only in the extreme situations were HI and nitrogen HI affected noticeably. In those treatments where there was a large second flush of pods, there was a pronounced biphasic pattern to pod number production, with HI also progressing through two distinct phases of increase separated by a plateau. The proportion of grain yield contributed to by biomass produced before pod filling varied from 0 to 61% with the contribution greatest under terminal water deficit. There was a larger effect of water deficit on N accumulation, and hence N-2 fixation, than on biomass accumulation. The study confirmed the applicability of a number of long-standing physiological concepts to the analysis of the effect of water deficit on mungbean, but also highlighted the difficulty of accounting for timing effects of water deficit where second flushes of pods alter canopy development, biomass and yield accumulation, and N dynamics. Crown Copyright (C) 2003 Published by Elsevier B.V. All rights reserved.

Wetting and the physiological responses of grain-fed cattle in a heated environment

A controlled crossover experimental design was used to determine the effect of altered water sprinkling duration on heifers subjected to heat stress conditions. Heifers were subjected to 3 days of thermoneutral conditions followed by 3 days of hot conditions accompanied by water sprinkling between 1300 and 1500 h (HOT1-3). Then on the following 2 days (HOT4-5), environmental conditions remained similar, but 3 heifers were sprinkled between 1200 and 1600 h ( WET) and 3 were not sprinkled (NONWET). This was followed by a 1-day period (HOT6) in which environmental conditions and sprinkling regimen were similar to HOT1-3. Rectal temperature (RT) was collected hourly, and respiration rate (RR) was monitored every 2 h on HOT Days 2, 4, 5, and 6. Dry matter intake and rate of eating were also determined. Sprinkling reduced RR and RT (P < 0.01) of all heifers during HOT1-3. During HOT4-5, WET heifers had lower (P < 0.05) RT than NONWET from 1300 to 700 h and lower RR from 1400 to 2000 h. Dry matter intake of NONWET heifers was reduced by 30.6% (P < 0.05) during HOT4-5 and by 51.2% on HOT6. On HOT4-5 the dry matter intakes of WET heifers were similar to intakes under thermoneutral conditions. During HOT6, RT was again reduced following sprinkling in all heifers. Comparison of RT and RR of NONWET and WET heifers on HOT1-3 v. HOT6 revealed that under similar environmental conditions, NONWET heifers had increased RT, partially due to carry-over from HOT4-5. However, NONWET heifers had 40% lower feed intake but tended to have lower RR on HOT6 v. HOT1-3. Only RR of WET heifers was greater on HOT6, possibly a result of switching from a 4-h back to a 2-h sprinkling period, while maintaining a 62% greater intake (5.80 v. 3.58 kg/day) than NONWET heifers during this time. Results suggest that inconsistent cooling regimens may increase the susceptibility of cattle to heat stress and elicit different physiological and metabolic responses.

Biomechanical and physiological comparison of conventional webbing and the M83 assault vest

This study compared the effect of load distribution using two different webbing designs on oxygen consumption and running kinematics of soldiers. It was hypothesised that running with webbing that distributes the load closer to the body (M83 Assault Vest) would expend less energy compared to running with conventional webbing (CON). Seven soldiers randomly completed three treadmill trials; an unloaded VO(2)max test, and two loaded (8 kg) efficiency tests using either the M83 or CON webbing. The VO(2)max test and the loaded efficiency tests had 4-min stages at 5, 8, 10 and 12km h(-1). Energy expenditure was measured via indirect calorimetry and video analysis was used to determine stride frequency (SF) and stride length (SL) during each trial. Participants using the M83 webbing expended significantly (p < 0.05) less energy at all four running velocities compared to the CON trials. The M83 webbing resulted in smaller changes to SL and SF from the unloaded trial when compared to the CON trial. These results indicate that the M83 vest that is designed to distribute the load closer to the body may have an energy efficiency advantage over conventional webbing when soldiers are running. (C) 2004 Published by Elsevier Ltd.

Physiological role of carnosine in contracting muscle

High-intensity exercise leads to reductions in muscle substrates (ATP, PCr, and glycogen) and a subsequent accumulation of metabolites (ADP, Pi, H+, and M2+) with a possible increase in free radical production. These factors independently and collectively have deleterious effects on muscle, with significant repercussions on high-intensity performance or training sessions. The effect of carnosine on overcoming muscle fatigue appears to be related to its ability to buffer the increased H+ concentration following high-intensity work. Carnosine, however, has other roles such as an antioxidant, a metal chelator, a Ca2+ and enzyme regulator, an inhibitor of protein glycosylation and protein-protein cross-linking. To date, only 1 study has investigated the effects of carnosine supplementation (not in pure form) on exercise performance in human subjects and found no improvement in repetitive high-intensity work. Much data has come from in vitro work on animal skeletal muscle fibers or other components of muscle contractile mechanisms. Thus further research needs to be carried out on humans to provide additional understanding on the effects of carnosine in vivo.

The effect of active immunization against adrenocorticotropic hormone on cortisol, beta-endorphin, vocalization, and growth in pigs

Because the poor growth performance of intensively housed pigs is associated with increased circulating glucocorticoid concentrations, we investigated the effects of glucocorticoid suppression by inducing a humoral immune response to ACTH on physiological and production variables in growing pigs. Grower pigs (28.6 0.9 kg) were immunized with amino acids 1 through 24 of ACTH conjugated to ovalbumin and suspended in diethylaminoethyl (DEAE) dextran-adjuvant or adjuvant alone (control) on d 1, 28, and 56. The ACTH-specific antibody titers generated suppressed increases in cortisol concentrations on d 63 in response to an acute stressor (P = 0.002; control = 71 +/- 8.2 ng/ mL; ACTH-immune = 43 +/- 4.9 ng/mL) without altering basal concentrations. Plasma beta-endorphin concentrations were also increased (P < 0.001) on d 63 (control = 18 +/- 2.1 ng/mL; ACTH-immune = 63 +/- 7.3 ng/mL), presumably because of a release from negative feedback on the expression of proopiomelanocortin in pituitary corticotropes. Immunization against ACTH did not alter ADG (P = 0.120; control = 1,077 25; ACTH-immune = 1,143 25 g) or ADFI (P = 0.64; control = 2,719 42; ACTH-immune = 2,749 42 g) and did not modify behavior (P = 0.681) assessed by measuring vocalization in response to acute restraint. In summary, suppression of stress-induced cortisol responses through ACTH immunization increased beta-endorphin concentrations, but it did not modify ADG, ADFI, or restraint vocalization score in growing pigs.

Impact of changes in natural ultraviolet radiation on pigment composition, physiological and morphological characteristics of the Antarctic moss, Grimmia antarctici

The impact of ambient ultraviolet (UV)-B radiation on the endemic bryophyte, Grimmia antarctici, was studied over 14 months in East Antarctica. Over recent decades, Antarctic plants have been exposed to the largest relative increase in UV-B exposure as a result of ozone depletion. We investigated the effect of reduced UV and visible radiation on the pigment concentrations, surface reflectance and physiological and morphological parameters of this moss. Plexiglass screens were used to provide both reduced UV levels (77%) and a 50% decrease in total radiation. The screen combinations were used to separate UV photoprotective from visible photoprotective strategies, because these bryophytes are growing in relatively high light environments compared with many mosses. G. antarctici was affected negatively by ambient levels of UV radiation. Chlorophyll content was significantly lower in plants grown under near-ambient UV, while the relative proportions of photoprotective carotenoids, especially beta-carotene and zeaxanthin, increased. However, no evidence for the accumulation of UV-B-absorbing pigments in response to UV radiation was observed. Although photosynthetic rates were not affected, there was evidence of UV effects on morphology. Plants that were shaded showed fewer treatment responses and these were similar to the natural variation observed between moss growing on exposed microtopographical ridges and in more sheltered valleys within the turf. Given that other Antarctic bryophytes possess UV-B-absorbing pigments which should offer better protection under ambient UV-B radiation, these findings suggest that G. antarctici may be disadvantaged in some settings under a climate with continuing high levels of springtime UV-B radiation.

Effect of smoke inhalation on viscoelastic properties and ventilation distribution in sheep

Smoke inhalation injuries are the leading cause of mortality from burn injury. Airway obstruction due to mucus plugging and bronchoconstriction can cause severe ventilation inhomogeneity and worsen hypoxia. Studies describing changes of viscoelastic characteristics of the lung after smoke inhalation are missing. We present results of a new smoke inhalation device in sheep and describe pathophysiological changes after smoke exposure. Fifteen female Merino ewes were anesthetized and intubated. Baseline data using electrical impedance tomography and multiple-breath inert-gas washout were obtained by measuring ventilation distribution, functional residual capacity, lung clearance index, dynamic compliance, and stress index. Ten sheep were exposed to standardized cotton smoke insufflations and five sheep to sham smoke insufflations. Measured carboxyhemoglobin before inhalation was 3.87 +/- 0.28% and 5 min after smoke was 61.5 +/- 2.1%, range 50-69.4% ( P < 0.001). Two hours after smoke functional residual capacity decreased from 1,773 +/- 226 to 1,006 +/- 129 ml and lung clearance index increased from 10.4 +/- 0.4 to 14.2 +/- 0.9. Dynamic compliance decreased from 56.6 +/- 5.5 to 32.8 +/- 3.2 ml/ cmH(2)O. Stress index increased from 0.994 +/- 0.009 to 1.081 +/- 0.011 ( P < 0.01) ( all means +/- SE, P < 0.05). Electrical impedance tomography showed a shift of ventilation from the dependent to the independent lung after smoke exposure. No significant change was seen in the sham group. Smoke inhalation caused immediate onset in pulmonary dysfunction and significant ventilation inhomogeneity. The smoke inhalation device as presented may be useful for interventional studies.