, suggesting that heat stress was the cause of growth reduction in bell pepper plants. Similarly, in tomato and tomatillo grown in Tifton, GA, like in this study, the use of dark mulches produced high RZTs resulting in reduced plant vegetative growth during the
Jun Song, Lihua Fan, Charles F. Forney, and Michael A. Jordan
Volatile emissions and chlorophyll fluorescence were investigated as potential signals of heat injury for apple [Malus sylvestris (L.) Mill. var. domestica (Borkh.) Mansf.] fruit. `McIntosh', `Cortland', `Jonagold', and `Northern Spy' apples were exposed to 46 °C for 0, 4, 8, or 12 hours (heat treatments). Following treatments, fruit were kept at 20 °C and evaluated after 1, 2, 4, or 7 days. Heat treatments induced volatile production including ethanol and ethyl acetate. The 8 and 12 hours heat treatments increased ethanol and ethyl acetate production in all four cultivars by as much as 170- and 11-fold, respectively, 1 day after treatments. Heat treatments also reduced ethylene production and chlorophyll fluorescence. Heat for 12 hours caused serious flesh browning. Among the cultivars investigated, `Northern Spy' and `McIntosh' were most susceptible to heat stress based on the degree of flesh browning. Correlation coefficients of heat stress induced ethanol emission and chlorophyll fluorescence with flesh browning were 0.82 and -0.66, respectively. The nondestructive measurements of ethanol emission and chlorophyll fluorescence have potential to identify stressed fruit with reduced quality or compromised storage life.
D. Michael Glenn, Amnon Erez, Gary J. Puterka, and Patricia Gundrum
Processed-kaolin particle films (PKPFs) are used commercially in large quantities on horticultural crops to repel insects, and reduce heat stress and solar injury of fruit. Our studies determined the effect of two processed-mineral particle film materials (kaolin and calcium carbonate), on whole plant carbon assimilation, water use efficiency, yield, mean fruit weight and quality in `Empire' apple [(Malus ×sylvestris (L.) Mill var. domestica (Borkh Mansf.))] over a four-year period. The application of a PKPF reduced canopy temperature, and probably reduced environmental stress, resulting in increased mean fruit weight and red color in two of the four years of the study. Whole canopy carbon assimilation studies indicated increased carbon assimilation only under conditions of high air temperature. The PKPF sprayed leaves also had reduced water use efficiency; likely due to increased stomatal conductance associated with reduced leaf temperature. Calcium carbonate had none of the positive effects of PKPF and reflected more photosynthetically active radiation (PAR) than the PKPF.
Ursula K. Schuch
vulnerability to heat stress Soc. Sci. Med. 63 2847 2863 Hurd, B.H. 2006 Water conservation and residential landscapes: Household preferences, household choices J. Agr. Res. Econ. 31 173 192 Levitt, D.G. Simpson, J.R. Tipton, J.L. 1995 Water use of two landscape
Ockert Greyvenstein, Brent Pemberton, Terri Starman, Genhua Niu, and David Byrne
than did BD (10.7 nodes). The heat stress treatments did not affect the number of vegetative nodes produced. Discussion Flower dry weight and flower abscission were most affected at the visible bud stage, which corresponds to stress treatments during
James W. Cross, Stacy A. Bonos, Bingru Huang, and William A. Meyer
overall turf quality of cool-season grasses during summer months is commonly referred to as summer stress. Summer stress can be broken down into two major components, heat stress and drought stress ( Huang et al., 1998a ; Jiang and Huang, 2000 , 2001b
Fenny Dane, A. Gene Hunter, and Oyette L. Chambliss
Selected tomato (Lycopersicon esculentum Mill) genotypes were evaluated for their fruit-setting ability under high-temperature field conditions. A temperature-controlled greenhouse study was conducted to determine the percent fruit set from the total number of flowers and fruit produced per plant. Ratings for set obtained under high-temperature field conditions were significantly (P = 0.001) correlated with percent fruit set determined under similar greenhouse conditions. Most of the Asian Vegetable Research and Development Center (AVRDC) selections, Beaverlodge lines, `Nagcarlan', and `Red Cherry' could be considered heat-tolerant. Small-fruited, abundantly flowering genotypes were less affected by heat stress than larger-fruited cultivars. Prolonged periods of high temperature caused drastic reductions in pollen fertility in most genotypes, except `Red Cherry' and L. esculentum var. cerasiforme (PI 190256). Stigma browning and stigma exsertion commonly occurred on all lines, except AVRDC CL-5915-553 and PI 190256. Diallel analyses indicated that pollen fertility and fruit set under high field temperatures were primarily under additive gene control.
V.M. Russo and J.C. Díaz-Pérez
Heat stress can limit yield in pepper (Capsicum spp.), generally through flower and fruit abortion. A kaolin-based particle film, originally developed to protect fruit trees from insects, has been found to reduce temperatures in tissues of plants. A kaolin-based particle film was tested to determine if it could be used to improve yields of pepper in Oklahoma and Georgia. In Oklahoma, seedlings of a bell pepper, `Jupiter', and a nonpungent jalapeño, `Pace 103', were transplanted at three progressively warmer planting dates from mid-May to mid-July 2002 and 2003, that would ensure that inflorescences would be subject to high day and night temperatures and treated with the kaolin-based particle film. Applications were begun as the first flowers were set and continued through the settings of the first three flushes of flowers on a three-times a week schedule, or on an as needed basis, to determine if the kaolin-based particle film improved yield. In Georgia, the bell peppers `Camelot' and `Heritage VR' were transplanted on 24 Apr. 2003, and treated with the kaolin-based particle film. In addition to yield, physiological measurements and disease incidences were recorded in Georgia. In both locations treatment with water only served as controls. In Georgia, the kaolin-based particle film had no significant effect on net photosynthesis, stomatal conductance, leaf transpiration or leaf temperature, as measured at midday on clear days. In Oklahoma, planting bell pepper after 15 May is not recommended. Planting the nonpungent jalapeño after mid-June can reduce yields. The kaolin-based particle film did not affect yield at either location and is not recommended for use on peppers.
D. Michael Glenn
); however, reducing canopy temperature can reduce heat stress and increase water use resulting in reduced water use efficiency and increased productivity ( Glenn, 2010 ). The reduction of PAR by the film at the leaf level is compensated in varying degrees
Abbas Lafta, Germán Sandoya, and Beiquan Mou
differences ( P < 0.0001) among the tested cultivars ( Table 2 ), indicating genetic variation for the traits under heat stress. These data confirmed a previous report of genetic variation for heat tolerance–related traits in eight crisphead lettuce cultivars