Effects of Nitrate and Potassium on Ammonium Toxicity in Cucumber Plants

ABSTRACT

Interactions between nitrate (NO₃ ^?), potassium (K⁺), and ammonium (NH₄ ⁺) were investigated using hydroponically grown cucumber (Cucumis sativus L.) plants. Ammonium as the sole nitrogen (N) source at 10 mM was toxic and led to overall growth suppression, chlorosis, and necrosis of leaves. After 20 days, 50% of the plants were dead. However, when NO₃ ^? was supplied at very low concentration together with high NH₄ ⁺ (only 1% of total 10 mM N) all seedlings survived and their growth was improved. High K⁺ concentration (5 mM) also alleviated NH₄ ⁺ toxicity and increased plant growth several fold compared to intermediate concentration of K⁺ (0.6 mM). Leaf total N and ¹⁵N derived from ¹⁵N-labelled NH₄ ⁺ increased in the presence of NO₃ ^?, but decreased at high K⁺ concentration. High K⁺ supply enhanced total carbon (C) and δ ¹³C and stimulated GS and PEPCase activities in leaves and roots. Nitrate supplementation had no effect on GS or PEPCase activities. It is concluded that K⁺ may alleviate NH₄ ⁺ toxicity, partly by inhibiting NH₄ ⁺ uptake, partly by stimulating C and N assimilation in the roots.     

Wild pistachio tree (Pistacia mutica) in the Qalajeh forest region of western Iran

Wild pistachio tree (Pistacia mutica) is considered the most important species in the Zagros forests. It can adapt to unfavorable environmental conditions. To find the suitable ecological conditions for pistachio species, we investigated different environmental factors such as gradient, aspect and position of the slopes through the distribution area. Frequency of pistachio trees in the north and northwest of Qalajeh forests was 36.4% and 1%, respectively. Maximum (32%) and minimum (13%) number of wild pistachio trees were in 30%–60% and >120% slope classes, respectively. The most number and least number of pistachio trees were found at elevations of 1100–1200 m and 2200–2300 m, respectively. The percentage of pistachio canopy coverage was 10. The average percentage of herbaceous coverage was 6.5. Pistachio trees of diameter per hectare at breast height (DBH) >20 cm numbered 5 while average number of pistachio trees was 8 per hectare. Pistachio seedlings per hectare averaged 3.5. The number of other species per ha was 7 trees. The effect of aspect on other species was not significant (p=0.151). Slope class and geographical aspect did not affect regeneration (p=0.275 and p=0.111, respectively). Pistachio plays an important economic role in semi-arid areas, therefore it is essential to protect and restore Qalajeh forests through participation by government and local people.     

Expression analysis of the genes involved in osmotic adjustment in bread wheat (Triticum aestivum L.) cultivars under terminal drought stress conditions

Osmotic adjustment is the main component for physiological machinery of wheat drought tolerance. Some of parameters implicated in osmotic adjustment in 15 bread wheat cultivars were evaluated at soil water deficits (50% FC) and FC as the control in the greenhouse. For the physiological traits, analysis of variance showed that there are highly significant differences between treatments, i.e. water stress levels and wheat cultivars. Shahpasand and Marvdasht as sensitive wheat cultivars had significantly lower osmotic adjustment, relative water content, K+ content, soluble sugar, proline, and glycine betaine levels than the rest of the cultivars. The results of cluster analysis revealed that all cultivars were grouped into three distinct clusters. Dez, Kavir, Pishtaz, and Maron cultivars which have the highest osmoregulation activity were in cluster I, whereas clusters II (Pishgam, Aflak, Hirmand, Zagros, and Vee/Nac) and III (Ws-89-2, Sardari, Azar2, Shapasand, and Marvdasht) had intermediate activity and the lowest capacities for osmoregulation, respectively. In addition, in wheat flag leaf during the reproductive stage under drought conditions, the changes in gene expression of two key genes namely P5CS (D-Pyrroline-5-carboxylate synthetase) and BADH (Betaine Aldehyde Dehydrogenase) in two selected cultivars including Dez and Marvdasht revealed that water stress can increase the expression level of the genes P5CS and BADH in the resistant cultivar, Dez, compared with Marvdasht, the sensitive one. In general, it seemed that application of the all cultivars in cluster I would enable breeders to acquire more reliable achievements under drought conditions.     

The use of pulsed-field gel electrophoresis to investigate the epidemiology of Mycoplasma bovis in French calf feedlots

Mycoplasma bovis is a major cause of respiratory outbreaks in cattle feedlots. In this study pulsed-field gel electrophoresis (PFGE) was used to trace field strains and provide information on M. bovis patterns of spread in calf feedlots. The suitability of KpnI, MluI and SmaI restriction enzymes was assessed on different sets of strains. The discriminative power of the first two enzymes was first assessed using 28 epidemiologically unrelated strains; stability was 100% on multiple isolates from in vivo experimental infection. Thirty-nine field isolates from six feedlots were then evaluated. In contrast to the unique fingerprints displayed by the unrelated strains, the isolates from the feedlots showed identical patterns at the time of the outbreak of respiratory disease and 4 weeks later. The PFGE typing results suggest that M. bovis strains follow a clonal epidemic spread pattern at the herd level and that the same strain persists in calves of the herd after the clinical signs have disappeared.     

Effect of canopy gap size and ecological factors on species diversity and beech seedlings in managed beech stands in Hyrcanian forests

We studied the species diversity of the herb layer and ecological factors in harvest-created gaps in beech stands under a single-tree selection system in Northern Iran. To determine diversity, the number of beech seedlings, and other ecological factors, 16 gaps were selected and subplots of 5 m2 were positioned at the centre and at the cardinal points of each gap. Species richness and Simpson diversity index increased with increasing gap area as did numbers of seedlings. With increasing humus layer thickness, species richness declined but the Hill evenness index increased. Species richness increased with increasing light availability. There was no relationship between crown radii of beech trees and diversity indices. Correlations between environmental factors and numbers ofindividuals of some species in the herb layer were not significant except in a few cases. The results help explain the effects of man-made gaps on the dynamics of managed beech stands and this benefits evaluation of silvicultural operating plans.     

Comparison of conventional and non-conventional techniques for the diagnosis of bovine brucellosis in Sudan

The objective of the present study was to detect brucellosis in suspected dairy cattle in Khartoum State, Sudan using the conventional serological tests and tests done on milk in comparison to a PCR-based technique. Milk and blood samples collected simultaneously from suspected brucellosis cows (n = 147) in 12 different dairy farms around Khartoum State were used in the study. Overall, 54 (36.7%) of the total milk samples were positive according to the milk ring test (MRT), while 29 (19.7%) of the serum samples were positive according to the Rose Bengal test (RBT); microscopy on modified Ziehl-Neelsen-stained slides detected 13.6% of the cases, and recovery of Brucella species on both Brucella medium and tryptic soya agar was 7.5%. Thirty-three (22.4%) samples were found positive on PCR-amplified IS711 which were then taken as positive brucellosis cases. The differences of RBT and PCR-IS711 from MRT were highly significant (P < 0.05). MRT detected more cases of bovine brucellosis compared to RBT, PCR, microscopy, and culture. MRT is recommended as a noninvasive test compared to RBT, and it is less expensive compared to PCR and culture.     

Sequence and phylogenetic analysis of neuraminidase genes of H9N2 avian influenza viruses isolated from commercial broiler chicken in Iran (2008 and 2009)

A total of 512 tissue samples collected from 30 farms located in various states of Iran during 2008–2009 as part of a program to monitor avian influenza viruses (AIVs) infection in Iran’s poultry population. To determine the genetic relationship of Iranian viruses, neuraminidase (NA) genes from ten isolates of H9N2 viruses isolated from commercial chickens in Iran during 2008–2009 were amplified and sequenced. The viruses’ neuraminidase gene was >90% similar to those of A/Quail/Hong Kong/G1/97 (H9N2) sublineage. The neuraminidase stalk regions in these Viruses had no deletion as compared to that of chicken/Beijing/1/94 sublineage (Beijing-like viruses) and the two human isolates A/HK/1073/99, A/HK/1074/99. Phylogenetic analysis of neuraminidase (NA) gene showed that it shares a common ancestor A/Quail/Hong Kong/G1/97 isolate which had contributed the internal genes of the H5N1 virus. The results of this study indicated that No (Beijing-like) virus and (Korean-like) virus were found in chickens in Iran, and the NA genes of H9N2 influenza viruses circulating in Iran during the past years were well conserved and the earlier Iranian isolates may be considered to represent such a progenitor.     

Water intake of laying hens after exposure to a warm climate

1. The water intake of laying hens was measured after exposure for 4 h to an ambient temperature (TA) of 35 or 40 degrees C. 2. Water intake increased continuously over 1 h but did not exceed a mean value of 80% of water lost by evaporation. There was considerable variation between birds.     

The effect of Rosa damascena essential oil on the amygdala electrical kindling seizures in rat

We investigated the effect of Rosa damascena Mill, essential oil on the development of induced amygdala kindling seizures. Male Wistar rats were implanted with one tripolar and two monopolar electrodes in right basolateral amygdala and dura surface, respectively. The control group was injected solvent of essential oil and two experimental groups were injected 750 and 1000 mg kg(-1) of essential oil (ip), 30 min before a daily kindling stimulation. The number of stimulations required for the first appearance of seizure stages was significantly larger in two experimental groups than in control group. Mean after discharge duration was significantly different and essential oil reduced the increase of after discharge duration. Mean after discharge amplitude was also shorter in the groups treated with essential oil than in control group. Duration time for 5th stage of seizure at fully-kindled rats was significantly shorter in two experimental groups than control group. These results suggest that Rosa damascena essential oil significantly retarded the development of seizure stages and possesses the ability to counteract kindling acquisition. The flavonoids of Rosa damascena may act via GABAA receptors as previous studies have proposed for flavonoids of other medicinal plants. More detailed studies are recommended to define the effective component(s) of Rosa on different types of epilepsy.