Levels Of Foliar Injury Research Articles

Effects of organic acids on paraquat activity in maize

In our previous study (Yoon et al., 2011, Pesticide Biochem. Physiol. 99: 65–76), we found that the level of foliar injury from paraquat (PA) in squash was generally less prevalent in younger leaves than in older ones. In addition, another previous study (Hyun et al., 2012, Korean J. Weed Sci. 32: 211–221) showed that the substance responsible for PA detoxification in young squash leaves was likely malic acid. Therefore, this study was conducted to investigate the effects of various organic acids on PA activity in maize. The levels of citric acid and malic acid in the fourth leaves were consistently higher than those in the first leaves in control and PA-treated leaves in both cultivars. In contrast, the level of tartaric acid in the first leaf was consistently higher than that of the fourth leaf in control and PA-treated leaves in both cultivars. Leaf injuries did not appear in maize treated with PA + malic acid at 0.3, 0.5, or 1%, PA + oxalic acid at 0.1, 0.3, 0.5, or 1%, PA + citric acid at 0.1, 0.3, 0.5, or 1%, or PA + tartaric acid at 1%. However, leaf injuries were observed in 69–82% of maize plants treated with 100 μM PA alone. The relative water contents in maize leaves were not reduced by PA + organic acid treatments compared with 100 μM PA treatment alone. Moreover, the superoxide and H2O2 contents in maize were significantly reduced by PA + most organic acids at various concentrations compared with 100 μM PA treatment alone. Moreover, MDA production in maize was significantly reduced by PA + organic acid treatments (except for PA + succinic acid) when compared with 100 μM PA treatment alone. Generally, chlorophyll contents in maize were not affected by treatment by PA alone or PA + organic acid. Taken together, these results suggest that squash plants contain organic acids such as malic acid and citric acid, which could nullify PA activity.

Pest intensity-crop loss relationships for the leafminer fly Liriomyza huidobrensis (Blanchard) in different potato (Solanum tuberosum L.) varieties

Quantifying the relationship between plant injury and yield loss is a critical component for decision making in integrated pest management (IPM). The effects of foliar injury during different growth stages of potato (Solanum tuberosum L.), caused by natural populations of the leafminer fly Liriomyza huidobrensis (Blanchard) on potato yield, and the economic injury level for potato varieties with different maturity times were studied in the Cañete valley on the central coast of Peru. Field experiments were carried out during the potato cropping season (July–November) in the years 2005, 2007 and 2008 using early, middle-late and late potato varieties. Insecticides with different control efficiencies or the use of varying numbers of insecticide applications obtained various levels of leafminer fly infestation intensities. Leafminer fly infestation caused foliar injury in all potato varieties resulting in yield losses, which varied, according to the seasonal adult flight activity in each year of evaluation, between 22% in 2007 (2508 adults/trap/season) and 51% in 2005 (3147 adults/trap/season). Foliar injury increased with the development and growth of the potato plant, with the highest injury registered at the end of the cropping period. Early varieties showed higher foliar injury and yield loss than late potato varieties with the exception of Maria Tambeña, which is considered partially resistant to leafminer fly infestation. Yield losses increased linearly by each percentage of foliar injury in all potato varieties. Critical point and multiple point models made it possible to identify the potato growth stage at which leafminer infestation had the greatest effect on yield. Pest infestation-crop loss relationships indicated that the accumulated foliar injury up to the growth stages of flowering and berry formation produced the highest yield losses in the different potato varieties. Economic injury levels varied according to control costs and commodity values in each potato variety (Desiree: 21–28%, Revolucion: 34–47%, Canchan: 31–40%, Maria Tambeña: 40–53%, Tomasa: 55–74%, and Yungay: 40–54% of foliar injury). Potato varieties can tolerate considerable levels of foliar injury by the leafminer fly before control measures are needed. The use of the economic injury levels is suggested as a decision support tool for managing the leafminer fly at reduced pest management costs.

Mechanism of paraquat tolerance in cucumber leaves of various ages

Differential sensitivity to paraquat was observed between cucumber cultivars and leaf age. Physiological responses to paraquat, including antioxidative enzyme activity, were investigated in leaf age classes of cucumber to identify mechanisms of paraquat tolerance. Leaf injury for ‘Naeseosamcheok’, ‘Daehandadagi’, ‘Baekgwangdadagi’, ‘Sangrokheukjinju’, and ‘Eunseongbaekdadagi’ cultivars was less than that of six other cultivars tested, averaged over leaf age and herbicide rate. The level of foliar injury caused by paraquat was Leaf 1 > 2 > 3 > 4 in seven of 11 cultivars used, where 4 was the youngest leaf. There was a positive correlation between leaf age and its relative susceptibility to paraquat, regardless of growth stage. Lipid peroxidation was less in the youngest leaf (Leaf 4) than in the older leaves at all herbicide concentrations. The youngest leaf had higher values for apparent photosynthesis than the oldest leaf. Differential leaf response to paraquat was partially correlated with the change in superoxide dismutase, ascorbate peroxidant, and glutathione reductase activities in treated leaves. Enzyme activity of ascorbate peroxidase (APX) was higher in Leaf 4 than in Leaves 1, 2, or 3 in untreated plants and after exposure to paraquat. APX isozymes were more abundant in treated than in untreated leaves and produced in higher amounts in younger than in older leaves. Application of ascorbate and glutathione before paraquat treatment protected cucumber leaves from paraquat injury.

Effect of post-emergence herbicide injury and planting date on yield of narrow-row soybean (Glycine max)

Some herbicides used post-emergence (POST) in soybean production cause foliar injury; however, new growth is normal and the crop does not appear to be further affected. Experiments were conducted to determine the effect of different levels of foliar injury caused by POST herbicides on yield of soybean cv. Maple Glen when planted early and late in a weed-free environment. Level of foliar injury was variable from year to year. Aciflurofen and imazethapyr caused foliar injury of 7 to 35% whereas, thifensulfuron and bentazon gave foliar injury ranging from 0 to 20% at 15 d after treatment (DAT). Foliar injury was short lived, and by 30 DAT had disappeared in 1994 and 1997, but still was visible at 11% for aciflurofen and 17% with imazethapyr on late-planted soybean in 1995. Aciflurofen- and imazethapyr-treated soybeans were still stunted at 30 and 60 DAT. Only imazethapyr reduced yields on both early- and late-planted soybean, in the 3 yr of the study. Yield of Maple Glen soybean was higher with early-planted soybean than with late-planted soybean in all years. Maximum yields were obtained in control plots kept weed free all season by a pre-emergence application of metribuzin. Key words: Aciflurofen; bentazon; imazethapyr; metribuzin; thifensulfuron; stunting; delayed maturity; foliar injury

Phytomonitoring and NO x pollution around silver refineries

In order to assess the impact of NO x pollution on vegetation around silver refineries, the present study was undertaken in Varanasi, India, during the period January to December 1994. For this purpose, the five most common plants at all sites, Ficus religeosa, Syzium jambolana, Azadirachta indica, Cassia fistula, and Mangifera indica, were selected as test plants. Five study sites were selected around silver refineries. A control site, BHU, was also selected outside the city in the northern direction at a distance of about 10 km. Responses to nitrogen oxides of plants, such as foliar injury symptoms, changes in chlorophyll, carotenoids, sugar, ascorbic acid, protein, and nitrogen content were measured. The NO x concentrations were high in the immediate vicinity of the silver refineries. There also exists a positive and significant relationship between the concentrations of NO x and foliar injury, protein, and nitrogen content in plants. The levels of foliar injury, chlorophyll, carotenoid, sugar, and ascorbic acid were found to decrease, and the amounts of protein and nitrogen were found to increase in comparison to plants growing at a control site. The magnitude of such changes was greatest in F. religeosa. The study suggests that the differential sensitivity of plants to NO x may be used in evaluating the air pollution impact around emission sources, and M. indica plants can be used as an indicator plant for quantifying the biological changes.

Phytomonitoring of air pollution around a thermal power plant

This study was undertaken in order to assess the impact of air pollutants on vegetation around Obra thermal power plant (1550 M W capacity) in the Mirzapur district of Uttar Pradesh. For this purpose, Mangifera indica, Citrus medico and Bouganvillaea spectabilis plants, most common at all sites, were selected as test plants. Five study sites were selected northeast (prevailing wind) of the thermal power plant. A control site was also selected at a distance of 30 km north of Obra. Responses of plants to pollutants in terms of presence of foliar injury symptoms and changes in chlorophyll, ascorbic acid and S content were measured. These changes were correlated with ambient SO 2 and suspended particulate matter (SPM) concentrations and the amount of dust settled on leaf surfaces. The SO 2 and SPM concentrations were quite high in the immediate vicinity of the power plant. There also exists a direct relationship between the concentration of SPM in air and amount of dust deposited on leaf surfaces. Maximum dust deposition was observed on M. indica plants. The levels of foliar injury, chlorophyll and ascorbic acid were found to decrease and that of S increase in plants around the power plant in comparison to those growing at a control site. The magnitude of such changes was maximum in M. indica and minimum in C. medica. A species specific direct relationship between the increase in the amount of S and decrease in chlorophyll content was observed. The study suggests that differential sensitivity of plants to SO 2 may be used in evaluating the air pollution impact around emission sources and M. indica plants can be used as an indicator plant for quantifying biological changes.

Effects of Metribuzin on Net Photosynthesis of Goosegrass (Eleusine indica) and Bermudagrass (Cynodonspp.)

The influence of metribuzin [4-ammo-6-tert-butyl-3-(methylthio)-as-triazin-5(4H)-one] on net photosynthesis of goosegrass [Eleusine indica(L.) Gaertn. ♯3ELEIN] and six cultivars of bermudagrass [Cynodon dactylon(L.) Pers. ♯ CYNDA cvs. ‘Common’, ‘Tufcote’, ‘Vamont’, and ‘Midiron’,Cynodon transvaalensisDavy., andCynodon dactylonXCynodon transvaalensis‘Tifway’] was evaluated. Metribuzin rapidly inhibited carbon dioxide (CO2) uptake within 1 h after application in both goosegeass and bermudagrasses. Very often, net photosynthesis was completely inhibited. Net photosynthesis in goosegrass was inhibited by lower rates of metribuzin than those required for similar reduction in bermudagrasses. Common, Tufcote, Tifway, andC. transvaalensisbermudagrasses were less sensitive to metribuzin than Midiron and Vamont based upon the degree of inhibition of net photosynthesis, the rate of its recovery, and the level of foliar injury. Recovery from inhibition of net photosynthesis was observed in both species 24 h after treatment with low metribuzin rates. High rates caused several days lag period before net photosynthesis resumed. After 10 days, 95% of the goosegrass foliage was injured (either chlorosis or necrosis) from 2 kg ai/ha metribuzin treatment. The threshold concentration for inducing leaf injury in bermudagrasses was 1 kg ai/ha. Inhibition of photosynthesis was initially rapid in both grasses; however, recovery was evident earlier and there was less foliar injury in bermudagrasses than in goosegrass. Selective control of goosegrass in bermudagrass may therefore be partially dependent upon rapid metabolism and/or inactivation of metribuzin in the bermudagrass.