Drought responses of above‐ground and below‐ground characteristics in warm‐season turfgrass

Water shortages have become more chronic as periodic droughts prolong and water demand for urban and agricultural use increases. Plant drought responses involve coordinated mechanisms in both above‐ and below‐ground systems, yet most studies lack comparisons of root and canopy responses under water scarcity and recovery. This is particularly true of research focused on warm‐season turfgrasses in sandy soils with extremely low water holding capacity. To address the lack of examination of coordinated stress and recovery responses, this study compared the above‐ and below‐ground plant responses during a dry‐down period of 21 days and recovery among four warm‐season turfgrass species in the field. Canopy drought responses and recovery were quantified using digital image analysis. In situ root images were captured using a minirhizotron camera system. Common bermudagrass [Cynodon dactylon (L.) Pers.] endured the entire drought period without losing 50% green cover while other species lost 50% green cover in 11–34 days predicted from the regression. The interspecific differences in drought resistance were mainly due to root characteristics. Other drought mechanisms appear to be responsible for differences identified in drought resistance between “Zeon” and “Taccoa Green” manilagrass [Zoysia matrella (L.) Merr.]. Recovery was delayed for up to 2 weeks in the second year, warranting further evaluation for turfgrass persistence under long‐term drought. Three‐week drought posed no threat to the survival of zoysiagrass. Species and genotypic variations were found in achieving full post‐recovery, which can be used to develop water conservation strategies and to adjust consumer expectations.     

Root architecture of sorghum genotypes differing in root angles under different water regimes

Plant root architecture offers the potential for increasing soil water accessibility, particularly under water-limited conditions. The objectives of this study were to evaluate the root architecture in two genotypes of sorghum (Sorghum bicolor (L.) Moench) differing in root angles and to assess the influence of different deficit irrigation regimes on root architecture. The response of two sorghum genotypes, ‘Early Hegari-Sart’ (EH; steep root angle) and ‘Bk7’ (shallow root angle) to four irrigation treatments was investigated in two replicated outdoor studies using large pots. The results indicated that EH possessed steeper brace and crown root angles, fewer brace roots, greater root biomass, and root length density than Bk7 at deeper soil depths (i.e., 15–30 and 30–45 cm) compared with a shallower depth (i.e., 0–15 cm). Across the soil profile, EH had greater root length density and length of roots of small diameter (<1 mm) than Bk7. Accordingly, EH showed more rapid soil-water capture than Bk7. Different levels of irrigation input greatly affected root architecture. Severe deficit irrigation (25% of full crop transpiration throughout the season) increased the angle and number of crown roots, root biomass, and root length density compared with 75 and 100% of full crop transpiration treatments. Consequently, root system architecture can be effectively manipulated through both genotypic selection and irrigation management to ensure optimal performance under different levels of soil available water.     

Present status and future strategy in breeding faba beans (Vicia Faba L.) for resistance to biotic and abiotic stresses

Progress is being made, mainly by ICARDA but also elsewhere, in breeding for resistance to Botrytis, AScochyta, Uromyces, and Orobanche; and some lines have resistance to more than one pathogen. The strategy is to extend multiple resistance but also to seek new and durable forms of resistance. Internationally coordinated programs are needed to maintain the momentum of this work.Tolerance of abiotic stresses leads to types suited to dry or cold environments rather than broad adaptability, but in this cross-pollinated species, the more hybrid vigor expressed by a cultivar, the more it is likely to tolerate various stresses.     

Ionic concentrations in a blanket peat bog in northern England and correlations with deposition and climate variables

Soil solution was collected to identify seasonal trends in its chemistry and to examine relationships between the concentrations of ions and variables that may control them. Samples were collected fortnightly at 10 cm and 50 cm depth in a blanket peat soil at Moor House–Upper Teesdale National Nature Reserve in the northern Pennine uplands of England. Dissolved organic carbon at 10 cm peaked each summer and correlated most strongly with temperature. At both depths Na⁺ and Cl^– were the dominant ions, reflecting the oceanic climate. Over the 3‐year sampling period, concentrations of the principal anions and cations at 10 cm varied little except during the autumns of 1994 and 1995 following unusually dry summers. At these times concentrations of SO₄^2–‐S increased from < 3 μmol to a maximum of 430 μmol and were balanced by smaller increases in Na⁺, Mg²⁺, Ca²⁺ and H⁺. The SO₄^2– concentration at 10 cm was most strongly correlated with depth to the water Table 3 weeks prior to sampling. At 50 cm depth in the peat a small increase in SO₄^2– occurred only during the autumn of 1995, and the concentration of SO₄^2– at this depth correlated most strongly with that at 10 cm. At neither depth were there any strong correlations with deposition. The increase in H⁺ concentration associated with the peak in SO₄^2– at 10 cm depth represents a fall in pH from usual values around 4.2 to 3.5.

Table 3. Deposition flux of ions in bulk precipitation at Moor House from weekly samplings 1994 to 1996 in kg ha^?1 year^?1. The UK flux is derived from 32 sites of the United Kingdom Precipitation Composition Monitoring Network 1992 to 1994 and the standard deviation (SD) relates to the variation between these sites ( Review Group on Acid Rain, 1997 )

Effects of the 1995–1997 drought on nitrate leaching in lowland England

Abstract. The effect of drought between summer 1995 and 1997 on stream and river nitrate concentrations was investigated using sites close to the long-running meteorological station in Oxford, UK. Nitrate concentrations in the River Windrush were relatively low during the drought, but after it had ended reached the highest level since records began in 1973. The low concentrations during the drought probably reflect a reduced contribution from agricultural runoff. High nitrate concentrations were found in a field drain at Wytham Environmental Change Network site during and after the drought, but discharge was greatly reduced. A woodland stream at Wytham had much lower nitrate concentrations than the field drain but these similarly increased during and after the drought. There was evidence that both a concentrating effect of low water volumes and enhanced soil nitrogen mineralization and nitrification rates were causing concentrations to rise. The effects of mineralization and nitrification were more important in woodland than agricultural land. Nitrate load over the course of a year was determined largely by discharge, but steeper gradients for the relationship between cumulative load and cumulative discharge were seen during and after the drought than before, reflecting the higher concentrations.     

Free chondral fragment involving the lateral trochlear ridge of the talus in a dog

A saucer-shaped defect involving the lateral trochlear ridge of the talus and a radiopaque joint fragment were evident on radiographs of the left tarsus in a 6-month-old Rottweiler. Surgical treatment involved removal of the joint fragment and debridement of the defect. Histologic interpretation of the specimen was a chondral fragment. It is important to realize the possibility of a lesion in the location described, as this may be an additional site for osteochondrosis dissecans of the canine tarsus.     

Dietary nano-chromium tripicolinate increases feed intake and decreases plasma cortisol in finisher gilts during summer

Chromium (Cr) is an essential mineral element and has been used in pig diets to improve growth performance, insulin sensitivity, immune response and carcase traits and to reduce heat or other stress responses. The aims of thiss study were to determine the impact of nano-sized chromium tripicolinate (nCrPic) on growth performance, feed efficiency and carcase characteristics of finisher gilts during the summer period. A total of 60 finisher Large White x Landrace gilts were stratified on initial weight and then within strata randomly allocated into two treatment groups in three replicates during mid-summer for 28 days. All pigs were housed in individual pens and had ad libitum access to feed and water. Pigs were fed either a control finisher diet (wheat-based diet containing 13.8 MJ digestible energy (DE) per kilogram and 0.56 g available lysine/MJ DE) or a control diet containing 400 ppb Cr as nCrPic. Dietary nCrPic supplementation increased feed intake by 6 % over the entire study (P?=?0.05). In particular, dietary nCrPic increased average daily feed intake (ADFI) by 8 % (P?=?0.02) during the final 2 weeks of the study. Moreover, dietary nCrPic tended to improve average daily feed (ADFI) over the entire study (P?=?0.09). However, there were no significant effects of nCrPic on feed conversion ratio (FCR), final weight, hot standard carcase weight (HCWT), P2 depth or dressing percentage. Plasma cortisol was decreased by 25 % (P?=?0.06) by dietary nCrPic supplementation. However, there were no effects of nCrPic on plasma glucose, insulin and nonesterified fatty acids (NEFA), might because of the higher feed intake. In conclusion, this study demonstrates that dietary nCrPic supplementation at 400 ppb can increase feed intake in finisher gilts during mid-summer, suggesting that nCrPic can ameliorate some of the negative effects of heat stress in pigs, possibly via decreased of circulating cortisol.