Heat stress induces and accelerates leaf senescence, which is characterized by a loss of chlorophyll and cellular membrane deterioration, as well as oxidative damage ( Jespersen et al. 2016 ; Liu and Huang 2000 ; Yu et al. 2021a ). Leaf
Heat and drought are two major factors limiting growth of cool-season grasses during summer. The objective of this study was to compare the effects of heat stress alone (H) or in combination with drought (H+D) on photosynthesis, water relations, and root growth of tall fescue (Festuca arundinacea L.) vs. perennial ryegrass (Lolium perenne L.). Grasses were exposed to H (35 °C day/30 °C night) or H+D (induced by withholding irrigation) in growth chambers for 35 days. Soil water content declined under H+D for both grasses but to a greater extent for fescue than for ryegrass. Declines in canopy net photosynthetic rate (Pn), leaf photochemical efficiency (Fv/Fm), and leaf relative water content (RWC) and the increase in electrolyte leakage (EL) were much more severe and occurred earlier for ryegrass than fescue subjected to both H and H+D and for both species than under H+D then H. Evapotranspiration (ET) rate increased to above the control level within 3 or 6 days of H and H+D for both species, but fescue had a higher ET rate than ryegrass at 3 and 6 days of H and 6 days of H+D. Root dry weight and viability in all soil layers decreased under H and H+D for both species. However, fescue had higher root dry weight and viability than ryegrass in the 20-40 cm layer under H and in both the 0-20 and 20-40 cm layers under H+D. The results indicated that maintenance of higher Pn, Fv/Fm, ET, RWC, and root growth and lower EL would help cool-season turfgrass survive summer stress, and that their characteristics could be used for selecting stress tolerant species or cultivars.
agricultural regions ( Sood et al., 2009 ). Temperature increase resulting from changing climatic condition is a serious threat ( Jones et al., 1999 ) that affects crop production. Heat stress occurs when temperatures are high enough to cause irreversible
Starting 2 weeks before anthesis of the first flower, tomato cultivars (Lycopersicon esculentum Mill.) differing in heat tolerance were exposed to mild heat stress (31/24 vs. 28/22 °C) at three levels of relative humidity (30%, 60%, and 90%) in controlled environment chambers at the Duke Univ. Phytotron. Pollen development in the anthers was followed cytologically, pollen release was measured at anthesis, and seed production and fruit weight were measured as fruit matured. Fruit and seed development were best at 60%RH and 28/22 °C and worst at 90% RH and 31/24. Seed development was poor at 31/24 °C at all humidity levels. It was also poor at 28/22 in the 90% RH treatment. Low relative humidity had a greater negtive effect on fruit and seed production and on cytological development in plants grown at high temperature. Pollen release was also reduced at 90% RH, with virtually no pollen released at 31/24 °C. Cytological examinations revealed developmental anomolies in pollen in some, but not all cultivars at 90% and 30% RH. Plant height was also affected by the treatments, with much taller plants in the high-temperature, high-humidity treatments.
wounding stress other than mowing. In addition, how the major hormones described in this paper respond to heat stress in turfgrass species is not well documented. Therefore, the objectives of the study were to evaluate hormone profiles in response to
transport. Cool-season turfgrass species such as Agrostis stolonifera are sensitive to heat stress and experience a series of physiological injuries when exposed to temperatures above 30 °C. Leaf senescence was observed after 20 d at 30 °C and only 8 d at
in March. To speed up establishment and increase early yields, Florida strawberry growers have recently begun to advance transplanting dates from mid October to late September. As a result, plants are exposed to even greater heat stress conditions
As plants are sessile organisms that cannot avoid heat, they often encounter harsh heat stress ( Wang et al., 2018 ). Heat stress can impose different metabolic and physical challenges on almost all aspects of plant development, growth, reproduction
node below the youngest, fully unfurled leaf because young and mature senescing tissues have different sensitivities to heat stress ( Karim et al., 1999 ; Marias et al., 2017 ). Dark-adapted F o and F V /F M measurements were performed after 10 h of
(20.2 °C and 125 mm rainfall in 2001 and 20.7 °C and 123 mm rainfall in 2002), the lettuce heads harvested within 50 and 51 d experienced 15 d (2001) and 19 d (2002) of heat stress above 28 °C. In the first planting of 2001, the susceptible parent had