Four Invasive Plant Species in Southwest Saudi Arabia Have Variable Effects on Soil Dynamics.

Predicting the direction and magnitude of change in soil dynamics caused by invasive plant species has proven to be difficult because these changes are often reported to be species- and habitat-specific. This study was conducted to determine changes in three soil properties, eight soil ions, and seven soil microelements under established stands of four invasive plants, Prosopis juliflora, Ipomoea carnea, Leucaena leucocephala, and Opuntia ficus-indica. Soil properties, ions, and microelements were measured in sites invaded by these four species in southwest Saudi Arabia, and these values were compared to the results for the same 18 parameters from adjacent sites with native vegetation. Because this study was conducted in an arid ecosystem, we predict that these four invasive plants will significantly alter the soil properties, ions, and microelements in the areas they invaded. While the soils of sites with the four invasive plant species generally had higher values for soil properties and ions compared to sites with native vegetation, in most instances these differences were not statistically significant. However, the soils within sites invaded by I. carnea, L. leucocephala, and P. juliflora had statistically significant differences for some soil parameters. For sites invaded by O. puntia ficus-indica, no soil properties, ions, or microelements were significantly different compared to adjacent sites with native vegetation. Sites invaded by the four plant species generally exhibited differences in the 11 soil properties, but in no instance were these differences statistically significant. All three soil properties and one soil ion (Ca) were significantly different across the four stands of native vegetation. For the seven soil microelements, significantly different values were detected for Co and Ni, but only among stands of the four invasive plant species. These results indicate that the four invasive plant species altered soil properties, ions, and microelements, but for most of the parameters we assessed, not significantly. Our results do not support our initial prediction, but are in general agreement with previous published findings, which indicate that the effects of invasive plants on soil dynamics vary idiosyncratically among invasive species and among invaded habitats.

Inheritance of heat tolerance in perennial ryegrass (Lolium perenne, Poaceae): evidence from progeny array analysis.

BACKGROUND: Heat stress is considered one of the most important environmental factors influencing plant physiology, growth, development, and reproductive output. The occurrence and damage caused by heat stress will likely increase with global climate change. Thus, there is an urgent need to better understand the genetic basis of heat tolerance, especially in cool season plants. MATERIALS AND METHODS: In this study, we assessed the inheritance of heat tolerance in perennial ryegrass (Lolium perenne L. subspecies perenne) , a cool season grass, through a comparison of two parental cultivars with their offspring. We crossed plants of a heat tolerant cultivar (Kangaroo Valley) with plants of a heat sensitive cultivar (Norlea), to generate 72 F1 hybrid progeny arrays. Both parents and their progeny were then exposed to heat stress for 40 days, and their photosynthetic performance (Fv/Fm values) and leaf H2O2 content were measured. RESULTS: As expected, Kangaroo Valley had significantly higher Fv/Fm values and significantly lower H2O2 concentrations than Norlea. For the F1 progeny arrays, values of Fv/Fm decreased gradually with increasing exposure to heat stress, while the content of H2O 2 increased. The progeny had a wide distribution of Fv/Fm and H 2O2 values at 40 days of heat stress. Approximately 95% of the 72 F1 progeny arrays had Fv/Fm values that were equal to or intermediate to the values of the two parental cultivars and 68% of the progeny arrays had H2O2 concentrations equal to or intermediate to their two parents. CONCLUSION: Results of this study indicate considerable additive genetic variation for heat tolerance among the 72 progeny arrays generated from these crosses, and such diversity can be used to improve heat tolerance in perennial ryegrass cultivars. Our findings point to the benefits of combining physiological measurements within a genetic framework to assess the inheritance of heat tolerance, a complex plant response.

Retinal detachment in renal insufficiency a report of 3 cases.

Three cases of retinal detachment associated with renal insufficiency are presented. The authors feel that dilutional hyponatremia and hypervolemia were not significant in the genesis of the detachments and that control of the blood pressure was the key factor in their cure. The importance of hypertensive retinochoroidopathy in the pathogenesis of the detachment is emphasized.

Electroretinographic alterations in retinal metallosis.

Electroretinographic responses can be modified by pathologic processes in two respects: response time and amplitude (or criterion threshold). Electrophysiologic syndromes can thus be defined. It is of clinical importance to recognize the effects of retinal metallosis on the electroretinographic response in cases of metallic intraocular foreign bodies: the sensitivity decreases while the response time remains normal for the intensity of stimulation. Iron appears to be more toxic than copper, but the secondary fibrosis induced by iron protects the retina more efficiently than that induced by copper.

Corneal scarring associated with daily soft contact lens wear.

Three young people developed scarring of the corneas in both eyes with loss of visual acuity while wearing cosmetic daily wear soft contact lenses. The condition was bilateral in all cases. The scarring began superiorly, spreading inferiorly, and was associated with signs of external inflammation, that is, conjunctival injection and corneal staining, when the patient first presented. The conjunctival injection resolved quickly on cessation of lens wear. However, the corneal staining and scarring were much slower to resolve. Two cases did eventually resolve completely. However, the other case was left with a permanent decrease in visual acuity, associated with a fairly marked induced astigmatism, secondary to the corneal changes. Possible etiologies of this condition are discussed, including allergies to chemicals and lens deposits or a hypoxic phenomenon. Induced astigmatism, secondary to soft contact lens wear, has previously been documented, apparently related to prolonged wearing time. These cases may be demonstrating the same phenomenon developed to a more advanced and serious stage.