Investigating the Reading Profiles of Middle School Emergent Bilinguals with Significant Reading Comprehension Difficulties.

Purpose: This study investigated the reading profiles of middle school Spanish-speaking emergent bilinguals (EBs) with significantly below grade level reading comprehension and whether these profiles varied in their reading comprehension performance over time. Method: Latent profile analyses were used to classify Grade 6 and 7 Hispanic EBs (n = 340; 39% female) into subgroups based on their word reading and vocabulary knowledge. Growth models were then fit within each profile to evaluate reading comprehension performance over time. Results: Analyses revealed four latent profiles emerged: (a) very low word reading and low vocabulary (10%), (b) low word reading and low vocabulary (71%), (c) average word reading and low vocabulary (16%), and (d) high word reading and low vocabulary (3%). Subgroups varied in their reading comprehension initially and over one year. Students in the subgroup marked by very low word reading and low vocabulary showed the lowest reading comprehension performance initially; however, they also showed the greatest growth over one year. Conclusion: These findings suggest there is heterogeneity in the reading skill profiles of Spanish-speaking EBs with reading comprehension difficulties. They also underscore the prevalence of word reading difficulties among these students. These may be important factors to consider when developing interventions to prevent and remediate these difficulties.

Assessment of ambient ozone effects on vegetation using snap bean as a bioindicator species.

Tropospheric ozone is an air pollutant that is toxic to plants, causing visible injury to foliage and a reduction in growth and yield. The use of plant bioindicators is one approach to assess the ozone impacts in diverse geographical areas. The objective of this study was to evaluate snap bean (Phaseolus vulgaris L.) as a potential bioindicator species. Three snap bean genotypes known to exhibit a range of ozone sensitivity were grown in pots under charcoal-filtered (CF) or nonfiltered (NF) treatments in open-top chambers, or under ambient air (AA) conditions. Treatment effects on biomass were not significant at 56 days after planting (DAP), but midseason foliar injury increased in the NF and AA treatments relative to CF controls. An increase in ozone from 25 to 30 nL L(-1) in CF controls to approximately 50 nL L(-1) in the NF and AA treatments was found to suppress final pod dry weight per plant by 40 to 60% in the most sensitive genotype S156. The same treatments suppressed final pod dry weight by 20 to 30% in a moderately sensitive genotype Oregon-91, and by 10% or less in a tolerant genotype R123. An S156 to R123 yield ratio of approximately one was observed under CF conditions. The S156 to R123 yield ratio declined to 0.6 to 0.7 in the NF treatment and declined further to 0.4 to 0.5 in the AA treatment, suggesting that ozone impact was underestimated in the open-top chambers. The results suggest that a snap bean bioindicator system has the potential to detect ambient ozone effects at present-day ozone concentrations.

Effects of Ethylenediurea on Snap Bean at a Range of Ozone Concentrations.

Ethylenediurea (EDU) [N-[2-(2-Oxo-1-imidazolidinyl)ethyl]-N'-phenylurea] often protects plants from visible foliar injury due to the air pollutant O3 , and it has been used to demonstrate yield losses from O3 under field conditions. A few studies, however, have indicated that EDU can suppress plant growth and yield. Because of the potential value of EDU as a research and assessment tool, controlled field experiments with snap bean (Phaseolus vulgaris L. 'BBL-290') were performed to test the effectiveness of different EDU application rates across a range of O3 concentrations. Four O3 concentrations were used in open-top chambers in each of two experiments [charcoal-filtered (CF) air, nonfiltered (NF) air, and nominal O3 additions of 0.025 and 0.05 or 0.03 and 0.06 µL L-1 O3 to NF air]. Ethylenediurea was added biweekly to the potting medium (four applications per experiment) as a soil drench. The EDU treatment concentrations were 0, 14, 28, 56, and 120 and 0, 8, 16, and 32 mg EDU (active) L-1 of potting medium in experiments one and two, respectively. Ethylenediurea provided some protection against O3 -induced foliar injury and growth suppression in both experiments. Measurements of net carbon exchange rate (NCER) and carbohydrate status of the tissues reflected the protective effects of EDU. In the first experiment, however, EDU caused visible foliar injury at some growth stages and suppressed growth. In the second experiment, visible foliar injury was not caused by EDU at any concentration, but pod biomass (yield) was suppressed by EDU in CF chambers. The differences in response to EDU between the experiments may have been due to environmental conditions (i.e., hot and dry during the first experiment and cooler during the second). Ethylenediurea also affected biomass partitioning in the plants grown in CF air (relative biomass was increased in leaves and decreased in pods). The results indicate that although EDU does protect or partially protect snap bean against O3 injury, it may also affect physiology and growth.

Adaptation of a white clover population to ozone stress.

White clover (Trifolium repens L.) 'Regal' and tall fescue (Festuca arundinacea Schreb.) 'Kentucky 31' were grown together in a field and exposed for two seasons in open-top chambers to six ozone (O3 ) regimes ranging from 0.59 to 1.95 times the ambient O3 concentration. Plants that survived were propagated clonally and used in the present study to determine whether selection for resistance or sensitivity to O3 had occurred. Relative foliar sensitivity of surviving clones to various short-term O3 , exposure regimes was determined with and without infection by several viruses. In tests of all surviving clones with viruses present, higher percentages of clones that survived two seasons at the high O3 levels were resistant to short-term exposure to O3 , than were those that survived exposure to the low O3 treatments. Only one of the 33 clones that survived exposure to charcoal-filtered air (059 treatment) was O3 -resistant while 19 of the 30 clones surviving the 1.95 treatment were O3 -resistant. Conversely, eight clones that survived the 0.59 treatment were sensitive to O3 while none of those that survived the l.95 treatment were sensitive. The results indicate that selection pressure in the presence of O3 stress was for resistance to O3 . Various combinations of five common viruses of clover were present among the surviving clones. Shoot-rip meristem culture was used to free one O3 -resistant and one O3 -sensitive clone from at) viruses. The relative O3 sensitivity of these two clones was not affected by viruses. Further testing is required to determine the relationships between relative foliar sensitivity to short-term O3 exposure and relative sensitivity to growth effects caused by long-term exposure.