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1.
The incidence of Botrytis cinerea Pers. was assessed on leaves, stems and fruits of tomato grown in night environments of 16°C with or without ventilation at night and 13°C with ventilation. Ventilation and temperatures by day were the same in all treatments. The experiment used nine independent glasshouse compartments in a row and column design. At 16°C, night ventilation gave significant reductions in grey mould on stems, leaves and fruits to c. 25% of that on unventilated plants. With night ventilation and a night temperature of 13°C, the incidence of B. cinerea on stems, leaves and fruit was doubled when compared with ventilated plants at 16°C. These differences could be explained partly in terms of the humidity which prevailed in the crops. No significant differences in yield were detected between treatments.  相似文献   

2.
Winter (vernalized) and summer (non-vernalized) timothy tillers were grown to anthesis in day/night temperature regimes of 32/26°, 27/21°, 21/15°, and 15/10°C. Herbage and total plant yields, total leaf-blade number and area, and total plant growth-rate were highest, or very nearly so, in the 21/15°C regime for both the winter and summer plants. However, summer plants reached anthesis 13 to 14 days later than winter plants in each temperature regime. Even though virtually all primary shoots produced an infiorescence, summer plants had significantiy more leaves and leaf-blade area, produced significantiy higher yields of leaf blade, stem plus sheath, stubble, and root tissues and had a significantly higher total plant growth rate than winter plants in each temperature regime.  相似文献   

3.
Summary In two indoor experiments under short day conditions, the effect of temperature during tuber bulking on dormancy of tubers was investigated for cvs Diamant and Désirée. Temperature treatments started after tuber initiation and lasted for 4 weeks, after which the haulm was removed. In Experiment 1, the day/night temperature regimes 18/12, 22/22, 26/18 and 32/12 °C (T18/12 etc.) were compared. In Experiment 2, three day temperatures (18, 24 and 30 °C) were combined with three night temperatures (12, 18 and 24 °C), resulting in nine treatments. The dormancy of cv. Diamant was shortest after very high day temperatures (30–32 °C), but intermediate day temperatures (22–26 °C) had no shortening effect compared to T18/12. Dormancy of cv. Désirée was not shortened, but rather tended to be prolonged by high temperatures (22–32 °C) during growth. High temperatures during growth resulted in more sprouts per tuber after dormancy had ended.  相似文献   

4.
Conyza bonariensis (L.) Cronq. is a problematic weed in crop and non-crop areas of California. This problem has been further aggravated by the discovery of herbicide-resistant biotypes. Experiments were conducted in 2012 and 2013 in fall and spring, respectively, to determine the efficacy of glyphosate, saflufenacil, and a tank-mixture of saflufenacil + glyphosate on glyphosate-susceptible (GS), glyphosate-resistant (GR), and glyphosate-paraquat-resistant (GPR) biotypes of C. bonariensis. Efficacy of the herbicides were evaluated at three growth stages (5- to 8-leaf seedling, rosette, and bolting); and three day/night temperature regimes (15/10 °C, 25/20 °C, 35/30 °C). Results differed between experiments conducted in the fall and spring. Saflufenacil-alone was more effective in the fall than in spring. All the GS, GR and GPR plants were controlled by saflufenacil-alone at the 5-to 8-leaf stage and rosette stage, but level of control declined at the bolting stage. Better control with saflufenacil-alone and glyphosate-alone was obtained at the 15/10 °C and 25/20 °C than at the 35/30 °C temperature regime. However, a tank-mixture of saflufenacil + glyphosate provided good control of the plants at 35/30 °C. Efficacy of saflufenacil-alone was inconsistent in spring and varied between the biotypes, but the control with saflufenacil + glyphosate was excellent and consistent between seasons. Glyphosate-alone provided good control of all three biotypes at the 5- to 8-leaf stage in the fall, but the control was poor in spring. Therefore, saflufenacil-alone can provide excellent control of C. bonariensis plants prior to the bolting stage in the fall; but in spring, it will be more effective when applied with glyphosate.  相似文献   

5.
《Field Crops Research》1986,15(2):97-108
In order to quantify the effects of mulch on soil temperature and soil moisture regimes during the growth of the potato crop, seven experiments were conducted at three contrasting hot tropical sites (latitude 5–12 °S) varying in altitude from 180 to 800 m. Mean maximum and minimum temperatures during the crop seasons ranged from 27° and 30° and 16° to 21°C respectively. Various mulches, mostly organic, were tested either singly or in combination with other agronomic practices, and in one experiment the interactions between mulch and three radiation levels (0, 50, and 75% reduction of incoming radiation) were studied.Mulch always enhanced soil moisture retention, but the improvement was less evident under increasing shade. Daily soil temperature fluctuations at tuber depth were damped by mulch, and maximum reduction of daytime soil temperature was recorded immediately following planting, before the crop emerged.Reductions of daytime soil heating and retention of heat within the soil at night by mulch were influenced by various edaphic and weather conditions. Maximum reduction during the day was achieved under conditions favouring soil heating (e.g. high irradiance, low soil moisture content, ridged soil, soil of low albedo) whereas heat retention at night by mulch, although greater in shaded than non-shaded plots, in general was relatively greater under conditions that favoured longwave re-radiation from the soil (e.g. ridged and dry soil).  相似文献   

6.
Potato (Solanum tuberosum L.) plantlets were conditioned in tissue culture to produce more minitubers when planted in a greenhouse. Tissue-cultured potato plantlets, varieties Coliban and Russet Burbank, were grown for 4, 10, or 12 weeks under three temperature regimes (22/18 °C, 16/10 °C, and 10/2 °C day/night) and a photoperiod of 16, 12, or 8 h in different stages of growth. Duration, temperature, and photoperiod of the in vitro period affected plantlet morphology and the total number of minitubers produced per plant in a greenhouse. Extending the growing period and introducing a hardening period with low temperatures (16/10 °C) during the in vitro production stage resulted in 97% more minitubers (4.94 vs 2.50 minitubers per plant for the control) in variety Coliban and up to 71% (6.50 vs 3.80 minitubers per plant for the control) in variety Russet Burbank. The total number of minitubers produced per plant did not change significantly for both varieties when a shorter photoperiod was used instead of the standard 16-h day during the growing period in vitro. Results presented in this experiment demonstrate that the number of minitubers can be substantially increased through the introduction of an induction period as an interstage between the in vitro stages of potato plantlet production and minituber production.  相似文献   

7.
Eight clones from a diploid hybrid population ofSolanum tuberosum subsp.phureja andstenotomum were grown at the Southeastern Plant Environmental Laboratories under simulated long day conditions under six day/night temperature regimes: 22/18, 22/14, 22/10, 26/18, 26/14 and 26/10 C. Time to bud initiation was not significantly affected by daytime temperature (22 vs 26 C). However, decreasing night temperature significantly increased the time to bud initiation. At 10 C night temperatures bud abortion was 100%, bud initiation failed to occur, or the initiated buds failed to flower before the end of the experiment for all clones except one. Bud abortion and flowering were not significantly affected by temperature regime in the remaining four chambers (26/18, 26/14, 22/18 and 22/14 C). However, there were highly significant differences in bud abortion and flowering among clones at the different temperature regimes.  相似文献   

8.
Scenarios of global climate change forecast an increase in air temperature of 3°C over the next 100 years in eastern Canada. Growth and nutritive value of cool‐season grasses are known to be affected by air temperature. It is also believed that grasses grown at high latitude have a greater nutritive value. The objectives of this study were to assess the effect of four combinations of day/night temperature and photoperiod (15 h–17/5°C; 15 h–22/10°C; 15 h–28/15°C; and 17 h‐17/5°C) on dry‐matter (DM) yield, in vitro true DM digestibility (IVTD), in vitro digestibility of neutral‐detergent fibre (NDF), and concentrations of NDF, acid‐detergent fibre (ADF), lignin, minerals and non‐structural carbohydrates (NSC) in timothy grown under controlled conditions. Furthermore, herbage was harvested in the morning and in the afternoon to assess the impact of the time of harvest. The dietary cation–anion difference [DCAD = (K+ + Na+) ? (Cl? + 0·6 S2?)] and the grass tetany index [GT index = K+/(Ca2+ + Mg2+)] were also calculated. Higher temperature regimes significantly decreased IVTD and digestibility of NDF but had a limited effect on concentrations of NDF, ADF and lignin. DM yield of herbage was less and the concentration of NSC was greater in timothy grown under a temperature regime of 28/15°C than the 17/5°C and 22/10°C regimes; this effect is mainly explained by a response to temperature stress. Values of DCAD and the GT index of herbage were also lower under the 28/15°C than the 17/5°C and 22/10°C regimes as a result of a decreased plant K concentration. Under the 17/5°C regime, an increase in 2 h of photoperiod resulted in increased DM yield, decreased concentrations of K, Ca, Mg, Cl and N, and an increased starch concentration; IVTD or digestibility of NDF were not affected, although lignin concentration was reduced. Harvesting timothy in the afternoon rather than in the morning resulted in higher NSC, mainly sucrose, concentrations, and decreased ADF and NDF concentrations. The forecasted increase in air temperature in eastern Canada over the next 100 years will result in lower yields and nutritive value of timothy.  相似文献   

9.
Abstract The nutritional value of Italian ryegrass (Lolium multiflorum) selection 121, bred for a high dry‐matter content and a high concentration of total non‐structural carbohydrate (TNC), was compared with that of Westerwolds ryegrass (L. multiflorum ssp. Westerwoldicum) cv. Midmar in a controlled environment. The concentration of neutral‐detergent fibre (NDF), acid‐detergent fibre (ADF), acid‐detergent lignin (ADL), nitrogenous compounds, minerals and in vitro digestibility were investigated as characteristics of nutritive value. The anatomical features of selection 121 and the Midmar cultivar were studied to determine possible structural differences. Thirty pots each of selection 121 and Midmar containing four plants per pot were arranged in a randomized block design in a controlled environment chamber. There were two temperature regimes during the study, the first being a warm regime (30 °C/20 °C) for 7 weeks followed by a cold regime(20 °C/7 °C) of a further 7 weeks. In the warm regime, the dry‐matter (DM) content and the TNC concentration of selection 121 were 0·17 and 0·16 higher, respectively, than Midmar. The NDF concentration was significantly (P < 0·01) higher in Midmar than in selection 121. When grown under warm conditions, Midmar had significantly (P < 0·001) higher concentrations of Mg, K, Na and Mn than selection 121. In the cold regime, the DM content and TNC concentration of selection 121 were 0·25 and 0·22 higher, respectively, than Midmar. No significant differences in the anti‐quality factors investigated were found between the two ryegrasses. In the cold regime, Midmar had significantly (P < 0·001 and P < 0·01) higher Ca, Mg, K, Na, Zn, Mn and P concentrations than selection 121. The results from this controlled environment study suggest that selection 121 is superior to Midmar in terms of the quality characteristics DM and TNC, and that these characteristics are not positively linked to anti‐quality factors associated with forage species.  相似文献   

10.
《Field Crops Research》1987,17(1):25-36
The effects of light quality, as used in photoperiod extension, on vegetative growth and floral development of pigeonpea [Cajanus cajan (L.) Millsp.] were studied using three photoperiod-insensitive lines, QPL2, Prabhat, and Hunt, and one photoperiod-sensitive line, Royes. Plants were grown in controlled-environment cabinets under day/night temperature regimes of 24/16°C (low) and 28/24°C (high) for 72 days after emergence (DAE). The five light treatments consisted of 12 and 16-h photoperiods and a 12-h photoperiod extended to 16 h with low-intensity lighting from either incandescent (I), fluorescent (F), or incandescent plus fluorescent (I+F) lamps.Little genetic variation occurred in vegetative response (main stem length and node number, leaf area and shoot dry weight) to extension light source. Response varied with temperature, plant age and growth stage. Main stem node appearance and stem extension tended to decline following floral initiation (FI), whereas leaf area and shoot dry weight accumulation increased rapidly after 35 or 42 DAE, irrespective of whether plants were vegetative or floral. Plants were larger under the high-temperature regime. Temperature altered plant response to extension light source. I-extension promoted growth under both temperature regimes, whilst I+F promoted growth under high temperatures but was unexpectedly inhibitory under low. Under high temperatures F extension was inhibitory prior to FI, but promoted later growth during floral bud development (FBD). Under low temperatures, F-extension was not inhibitory during the pre-initiation phase.The four genotypes differed in their floral response to extension light source, the effect on initiation and development of floral primordia varying dependent upon temperature. Low temperatures resulted in sensitivity to extension light source, delaying FI and FBD. In Royes, failure to initiate under low temperatures was associated with small plant size (≤3.5 g shoot dry weight). High temperatures tended to negate the delaying effects of extension light source, but resulted in photoperiod sensitivity, delaying FI in the early-flowering lines QPL-2 and Prabhat. Under high temperatures, Royes was insensitive (FI and FBD) to extensions containing incandescent light (I, I+F). Under high temperatures, time of flowering was least affected by incandescent extensions (I, I+F), and most by F-extension, which delayed FBD in all lines. Under low temperatures, I+F extensions resulted in the greatest variation in flowering time.It was concluded that where heterogeneity exists in floral response to the intensity and/or quality of light, use of artificial lighting to select for photoperiod sensitivity may lead to misclassification.  相似文献   

11.
Anthracnose disease of papaya, caused by Colletotrichum gloeosporioides Penz, can cause extensive postharvest losses. The goal of this research was to use pre-harvest calcium applications to reduce anthracnose disease. Six pre-harvest foliar calcium sprays were applied biweekly to papaya trees in experimental orchards at Universiti Putra Malaysia. Additional in vitro and in vivo tests were carried out to test the effect of calcium on fruit calcium content, spore germination, mycelial growth and disease severity. Calcium chloride at 1%, 1.5% and 2.0% concentrations significantly decreased spore germination. Calcium content of papaya fruit was significantly increased by calcium sprays at a concentration of 2.0% in 2012 and 2013. In vivo studies showed that increasing calcium content in fruit by calcium sprays at 1.5 and 2.0% concentrations significantly reduced anthracnose incidence of fruits during five weeks storage at 12 ± 2 °C, and delayed initiation of disease symptoms by four weeks.  相似文献   

12.
A study was conducted to determine the feasibility and advantages of wound-healing potatoes at lower than recommended temperatures. The progress of wound-healing at 6, 9, and 16°C, of tissue taken from Russet Burbank potato tubers, was evaluated by inducing weight loss with high temperature or decay organisms following various curing intervals. Increasing the wound-healing temperature resulted in a greater resistance to weight loss and a decreased susceptibility to infection byErwinia carotovora subsp.carotovora. Resistance to weight loss increased as wound-healing temperature increased following 6 and 16 day intervals. However, weight loss induced after 21 days of healing appeared to level off at 9°C indicating maximum development of a wound barrier. Loss due to rot, after inoculation of fresh cores withE. carotovora, was directly proportional to incubation time and temperature. When wound-healing progress was measured by loss of fresh weight induced by elevated temperatures or rot, the advantages of woundhealing at 16°C compared with 9°C decreased significantly after 21 days of curing. Wound-healing at approximately 9°C for 25 days was found to be the best compromise temperature for keeping rot progress and weight loss at a minimum while allowing the process of healing and maturation to occur.  相似文献   

13.
Summary In pot culture experiments over 2 consecutive years, 20 potato genotypes of varying heat tolerance were grown under long day conditions and heat stressed by being exposed to high (38 °C/21 °C mean day/night) temperature. The percent increase in mean internode length of heat stressed plants over those grown at normal temperatue (25°C/16°C day/night) was correlated with the percent tuber dry matter yield of the heat stressed plants (r=0.618, P=0.01). In the same 20 genotypes, grown under short day conditions at normal temperature, the fraction of leaf bud cuttings exposed to high night temperature (23°C) that produced tuber initials correlated with the percentage increase in internode elongation in stem cuttings exposed to 25°C compared with those exposed to 15°C (r=0.680. P=0.01). Thus the relative changes in internode elongation are related to thermal tolerance, and it is suggested that this can be used as a selection criterion for heat tolerance.  相似文献   

14.
Cuphea (Cuphea viscosissima Jacq. x C. lanceolata W.T. Aiton; PSR23) is a new oilseed crop rich in medium-chain fatty acids similar to tropical palms. Agronomic studies suggest that temperature is a key determinant of cuphea seed yields. However, little is known about the growth and photosynthesis response of cuphea to temperature. The following study is the first of its kind to evaluate cuphea's growth and photosynthesis response to temperature. Cuphea was grown under day/night temperature regimes of 18/12, 24/18, and 30/24 °C and regression analysis was used to assess its responses of growth and photosynthesis and determine their optimum temperature range. Vegetative growth and leaf photosynthesis adapted well over the temperature range studied. However, reproductive growth was more sensitive showing a decline with increasing temperature. Reproductive growth rate was greatest under the lowest (18/12 °C) temperature treatment and declined by 43% at the highest growth temperatures. In contrast, vegetative growth, which was greatest under the 24/18 °C treatment, declined by just 25 and 10% at the lowest and highest temperatures, respectively. Photosynthesis acclimated to temperature by up-regulation of in vivo Rubisco activity with declining growth temperature. Maximum Rubisco activity (Vcmax) in leaves under the 18/12 °C treatment was 76% greater than that of leaves grown at 30/24 °C. Photosynthetic acclimation permitted cuphea to vegetatively grow well over a wide temperature range, but does not explain the sensitivity of reproductive growth to temperature, which will require further research to elucidate.  相似文献   

15.
Carotenoids are natural compounds whose nutritional importance comes from the provitamin A activity of some of them and their protection against several serious human disorders. The degradation of carotenoids was investigated during apricot drying by microwave and convective hot-air at 60 and 70 °C. Seven carotenoids were identified: antheraxanthin, lutein, zeaxanthin, β-cryptoxanthin, 13-cis-β-carotene, all-trans-β-carotene and 9-cis-β-carotene; among these, all-trans-β-carotene was found to be about 50 % of total carotenoids. First-order kinetic models were found to better describe all-trans-β-carotene reduction during drying, with a degradation rate constant (k1) that increased two folds when temperatures increased by 10 °C, in both methods. No differences were found in k1 between apricots dried by hot air at 70 °C (k1?=?0.0340 h?1) and by microwave at 60 °C. The evolution of total carotenoids (117.1 mg/kg on dry basis) during drying highlighted a wider decrease (about 50 %) when microwave heating was employed, for both set temperatures. Antheraxantin was found to be the carotenoid most susceptible to heat, disappearing at 6 h during both trials with microwave as well as during convective hot-air at 70 °C. For this reason, antheraxanthin could be a useful marker for the evaluation of thermal damage due to the drying process. Also the degree of isomerization of all-trans-β-carotene could be a useful marker for the evaluation of the drying process.  相似文献   

16.
High temperature stress during ripening increases the frequency of chalky grains, resulting in a lower market value for rice (Oryza sativa L.). Changes in starch properties and the accumulation pattern of storage proteins are proposed to be related to the occurrence of chalky grains. This study investigated changes in the accumulation of key storage compounds in the grains of Japanese highly palatable rice cultivars, subjected to high temperature stress when grown in a growth chamber and the field. The 13 kDa prolamin content was significantly reduced in a highly heat-sensitive cultivar, Tsukushiroman, whereas the 13 kDa prolamin content was not affected in a heat-tolerant cultivar, Genkitsukushi, even in a high temperature chamber condition (31/26 °C day/night), when compared with the control chamber condition (26/21 °C day/night) for both genotypes. In addition, grains grown in field conditions revealed that severely chalky grains had less 13 kDa prolamin than perfect grains in all five genotypes. Changes in amylose content and the distribution of amylopectin chain lengths did not explain the difference in grain appearance both for chamber and field experiments. These results strongly suggest that physiological processes linked with the synthesis of 13 kDa prolamin are associated with grain appearance in Japanese highly palatable under high temperature stress.  相似文献   

17.
The longevity and fecundity of the overwintered arrowhead scale, Unaspis yanonensis (Kuwana) (Hemiptera: Diaspididae), was examined at constant temperatures. The total fecundity increased up to 24 °C and declined thereafter. Total fecundity reached a maximum of 260.9 eggs per female at 24 °C. Females demonstrated periodic oviposition activity but the pattern differed with temperature. The first cycle of fecundity was not significantly different between 16 and 28 °C. However, fecundity in the latter cycles, measured at rearing temperatures of 16, 20 and 32 °C, was lower than at 24 and 28 °C. The pre-oviposition period ranged from 49.0 d at 16 °C to 19.7 d at 32 °C, and was shortest (19.4 d) at 28 °C. The longevity was found to be greatest (87.3 d) at 16 °C and was as short as 48.9 d at 32 °C. Regression of the mean development rate vs. temperature provided a low-threshold temperature estimate of 8.7 °C for the pre-oviposition stage and a thermal constant of 358.4 degree days. The theoretical low threshold temperature and thermal constant applied to the calculation for the completion of the U. yanonensis pre-oviposition period predicted the appearance of first crawlers in the field.  相似文献   

18.
A study was conducted to determine the effect of different soil temperatures on the development of brown center in potatoes,Solanum tuberosum L. cv Russet Burbank. Plants were grown in 19 liter (5-gal) nursery pots under warm conditions, previously shown to be non-inductive to brown center development, until shortly after tuber formation. They were then moved to a cool growth room and grown in 4 soil temperature regimes until harvest. Soil temperatures of 10°C (50°F) and 15°C (60°F) produced greater development of brown center than either 4°C (40°F) or 21°C (70°F).  相似文献   

19.
Since 1971, we have used roquette,Eruca vesicaria (L.) Cav. subsp.sativa (Mill.) Thell., as a host for prolonged maintenance of colonies of the green peach aphid,Myzus persicae (Sulzer), and the potato aphid,Macrosiphum euphorbiae (Thomas). When roquette plants were kept in a growth chamber with 12 hour light and dark periods and a temperature regime of 20°C light and 15°C dark, or in greenhouse cubicles with temperatures ranging from 22–28°C and light periods ranging from 12 to 14 hours, colonies of these aphids could be maintained on a single plant for 16 weeks. These aphids retained their original characteristics, readily accepting radish, lettuce, and snapdragon as hosts, but accepted chrysanthemum only with great reluctance. Aphids from colonies that were maintained on roquette for 4 years did not lose their ability to transmit viruses.  相似文献   

20.
Near neutral (pH = 6.3-6.5) electrolyzed oxidizing water (EO water) has been demonstrated to inactivate fungi in pure culture and to mitigate infection on fruit surfaces. One possible alternative or supplement to traditional pre-harvest crop management practices that currently rely on the use of large quantities of fungicides is near neutral EO water. In the present work, treatment of Botrytis cinerea or Monilinia fructicola with near neutral EO water (50 or 100 ppm total residual chlorine (TRC)) in pure culture resulted in a 106 reduction and 100% inactivation as evidenced by negative broth enrichment. When applied in concert with 50 or 100 ppm EO water, treatments of Captan 50WP (captan), Rovral (iprodione), Iprodione 4LAG (iprodione), or Switch 62.5 WDG (cyprodinil and fludioxonil) effectively inhibited fungal growth of B. cinerea as evidenced by a 106 reduction on the direct plate and negative broth enrichment. Treatments of Captan 50WG (captan), Rovral (iprodione), Iprodione 4LAG (iprodione), Switch 62.5 WDG (cyprodinil and fludioxonil), Captan 80 WDG (captan), or Captevate (captan and fenhexamide) when applied in concert with 50 or 100 ppm EO resulted in a 106 reduction of M. Fructicola and 100% inactivation as evidenced by negative broth enrichment. Strawberry plants sprayed with EO water (pH = 6.3-6.5) at concentrations of 50 and 100 ppm TRC once per week, did not result in significant (P > 0.05) phytotoxicity relative to a water (0 ppm TRC) treatment. In this study, the application of 100 ppm EO water (pH = 6.3-6.5) twice per week to strawberry plants infected with B. cinerea was more effective (P ≤ 0.05) than a once per week Captan application and as effective as a once per week captan/once per week EO treatment. The once per week captan/once per week EO treatment was significantly more effective (P ≤ 0.05) than the captan once per week treatment. Dip treatments of strawberries in near neutral EO solutions (50 and 100 ppm TRC; pH = 6.3-6.5) did not leave a chlorine residue on the fruit relative to a water dip. The results from this study suggest that near neutral EO solutions could be used to manage infection of B. cinerea on strawberry plants in the field and also as a disinfection solution for harvesting equipment, greenhouses, packing houses and in commercial facilities to prevent or manage infections of B. cinerea and M. fructicola.  相似文献   

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