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Strawberries are a very important economic crop; thus, a lot of research has been conducted on several production areas. However, phenological performance is still lacking information, especially when it comes to modeling. Therefore, this study aims to develop a phenological model for flower–fruit development under hydroponic conditions to support growers' decision-making. Two day-neutral cultivars, 'Albion' and 'San Andreas', were established in a drip hydroponic system in Auburn, Alabama for the 2022–2023 production season. Phenological data were collected daily on 30 flowers per cultivar for three periods (Oct 25–Dec 16, Dec 27–Feb 21, and Feb 28–Apr 16). Weather data were obtained from a weather station placed in the greenhouse. Growing degree days (GDD) accumulation was calculated for each stage and cycle using a base temperature (Tb) of 3 °C. The Gaussian model was adjusted for each stage and cycle using a non-linear procedure to obtain Gaussian curves. Simulations were made for the model assuming temperature would increase or decrease by 1 °C. Six stages were identified, and their cycle ranged from 43–56 days to be accomplished. 'Albion' needed more days to reach maturity, with 51, 56, and 47 days, and 'San Andreas' took 43, 54, and 46 days for cycles 1, 2, and 3 respectively. In addition, for cycles 1 and 2, not all the buds reached maturity, as expected. Stage 5 (fruit formation) needed more days than the rest of the stages to be completed. Because of the different starting dates for each cycle, the starting GDD was different as well. A sensitivity analysis simulation of the model showed that if temperature decreases by 1 °C, the GDD accumulated to complete the stages would be less (same dates), and it would be more if the temperature increased by 1 °C. The opposite happened with the days, if the temperature increased by 1 °C, the duration of the stage decreased, and it would increase if the temperature decreased by 1 °C, affecting stages 4, 5, and 6. Overall, 'San Andreas' performed better than 'Albion' under hydroponic conditions during three productive cycles. [ABSTRACT FROM AUTHOR]

The commercial apple production in Norway is limited to the small regions along the fjords in the southwest part of the country and around lakes or near the sea in the southeast with favorable climate. Due to the rapid rate of climate change over the recent decades, it is expected that suitable heat conditions for apple growing will expand to the areas that were previously too cold. This study analyses the heat suitability of future climate (2021–2100) under the RCP8.5 scenario for 6 common apple varieties in Norway: Discovery, Gravenstein, Summerred, Aroma, Rubinstep and Elstar. Previously established heat requirement criteria (based on the temperature threshold for the full blooming and growing degree days sum between the full bloom and harvest) are applied to the temperature outputs of the regional climate models downscaled to 1 km resolution. The assessment indicates that as temperature rises, heat conditions suitable for cultivation of all 6 apple varieties will expand. According to the ensemble median value, areas with the favorable heat conditions for growing at least one of the considered apple varieties will increase 25 times in the period 2021–2040 and 60 times in the period 2041–2060, compared to the referent period 1971–2000. At the same time, areas suitable for all 6 apple varieties will increase 3 times in the first, and 3.8 times in the latter period. The favorable areas will advance from south and southeast northwards and inland in the eastern region, along the west and northwestern coastline towards higher latitudes, and along continental parts of fjords. The fastest expansion of heat suitable conditions is expected for Discovery and Gravenstein. The findings of this study are relevant for zoning apple production future potential and for strategical planning of climate change adaptation measures within the sector. Weather-related risks, such as risks from winter low temperatures, spring frost, drought and extreme precipitation were not considered. [ABSTRACT FROM AUTHOR]

Flowering in temperate fruit trees depends on the temperatures during the previous months; chill is required to overcome endodormancy, and then heat exposure is needed. These agroclimatic requirements are cultivar-specific and determine their adaptability to the growing area and their response to climate change. We aim to estimate the agroclimatic requirements of 16 traditional cultivars of European pears grown in Zaragoza (Spain). We used Partial Least Squares regression analysis to relate 20-year records of flowering dates to the temperatures of the 8 previous months. This approach allowed us to establish the chilling and forcing periods, through which we quantified temperatures with three models for chill accumulation (Chilling Hours, Utah model, and Dynamic model) and one model for heat accumulation (Growing Degree Hours). The results indicated very little difference in the chilling and forcing periods. Chill requirements ranged from 43.9 to 49.2 Chill Portions; from 1027 to 1163 Chilling Units; and from 719 to 774 Chilling Hours. Heat requirements ranged from 6514 to 7509 Growing Degree Hours. Flowering dates were mainly determined by the temperatures during the chilling period. This means that reductions in winter chill caused by global warming in many regions could cause flowering delays or even failures in the fulfillment of chill requirements. [ABSTRACT FROM AUTHOR]

Strawberries are a very important economic crop; thus, a lot of research has been conducted on several production areas. However, phenological performance is still lacking information, especially when it comes to modeling. Therefore, this study aims to develop a phenological model for flower–fruit development under hydroponic conditions to support growers’ decision-making. Two day-neutral cultivars, ‘Albion’ and ‘San Andreas’, were established in a drip hydroponic system in Auburn, Alabama for the 2022–2023 production season. Phenological data were collected daily on 30 flowers per cultivar for three periods (Oct 25–Dec 16, Dec 27–Feb 21, and Feb 28–Apr 16). Weather data were obtained from a weather station placed in the greenhouse. Growing degree days (GDD) accumulation was calculated for each stage and cycle using a base temperature (Tb) of 3 °C. The Gaussian model was adjusted for each stage and cycle using a non-linear procedure to obtain Gaussian curves. Simulations were made for the model assuming temperature would increase or decrease by 1 °C. Six stages were identified, and their cycle ranged from 43–56 days to be accomplished. ‘Albion’ needed more days to reach maturity, with 51, 56, and 47 days, and ‘San Andreas’ took 43, 54, and 46 days for cycles 1, 2, and 3 respectively. In addition, for cycles 1 and 2, not all the buds reached maturity, as expected. Stage 5 (fruit formation) needed more days than the rest of the stages to be completed. Because of the different starting dates for each cycle, the starting GDD was different as well. A sensitivity analysis simulation of the model showed that if temperature decreases by 1 °C, the GDD accumulated to complete the stages would be less (same dates), and it would be more if the temperature increased by 1 °C. The opposite happened with the days, if the temperature increased by 1 °C, the duration of the stage decreased, and it would increase if the temperature decreased by 1 °C, affecting stages 4, 5, and 6. Overall, ‘San Andreas’ performed better than ‘Albion’ under hydroponic conditions during three productive cycles.

The commercial apple production in Norway is limited to the small regions along the fjords in the southwest part of the country and around lakes or near the sea in the southeast with favorable climate. Due to the rapid rate of climate change over the recent decades, it is expected that suitable heat conditions for apple growing will expand to the areas that were previously too cold. This study analyses the heat suitability of future climate (2021–2100) under the RCP8.5 scenario for 6 common apple varieties in Norway: Discovery, Gravenstein, Summerred, Aroma, Rubinstep and Elstar. Previously established heat requirement criteria (based on the temperature threshold for the full blooming and growing degree days sum between the full bloom and harvest) are applied to the temperature outputs of the regional climate models downscaled to 1 km resolution. The assessment indicates that as temperature rises, heat conditions suitable for cultivation of all 6 apple varieties will expand. According to the ensemble median value, areas with the favorable heat conditions for growing at least one of the considered apple varieties will increase 25 times in the period 2021–2040 and 60 times in the period 2041–2060, compared to the referent period 1971–2000. At the same time, areas suitable for all 6 apple varieties will increase 3 times in the first, and 3.8 times in the latter period. The favorable areas will advance from south and southeast northwards and inland in the eastern region, along the west and northwestern coastline towards higher latitudes, and along continental parts of fjords. The fastest expansion of heat suitable conditions is expected for Discovery and Gravenstein. The findings of this study are relevant for zoning apple production future potential and for strategical planning of climate change adaptation measures within the sector. Weather-related risks, such as risks from winter low temperatures, spring frost, drought and extreme precipitation were not considered.

Aim: This research aimed to: (1) investigate the relationships between harvest dates and berry composition with air temperature during important periods during the growing season, across a range of indigenous and international winegrape varieties grown in wine regions over the majority of Greece; (2) calculate growing degree-days (GDD) from 1st of April until the harvest date of each variety and group the winegrape varieties according to their heat requirements; and (3) predict future harvest dates based upon these heat requirements under different representative emission pathways (i.e., RCP4.5 and RCP8.5) and future time periods (2041-2065 and 2071-2095) using an ensemble projection dataset. Methods and results: The analysis of heat requirements based on GDD from 1st of April to harvest date identified consistent maturity groups of the varieties studied, especially for indigenous Greek varieties. Trend analysis using the basic linear regression model showed that harvest dates have shifted earlier, during the last few decades, due to warmer conditions (especially during the ripening period) in most cases. In addition, trends in potential alcohol (acid) levels were found to be positively (negatively) correlated with maximum air temperatures in the majority of cases. Analysis of future projections using a global multi-climate model ensemble dataset (10 regional climate models) showed that harvest dates are projected to shift earlier up to 40 days in two future time periods (i.e., 2041-2065 and 2071-2095) depending on the variety and the emission pathway. Conclusions: Harvest dates of the early ripening varieties were associated more with the variations in maximum air temperatures during March to July, while mid- and late ripening varieties appeared to be affected more by maximum air temperatures during the ripening period. In addition, late ripening, mostly indigenous, varieties were less impacted by temperature increases compared to international varieties. Significance of the study: The indigenous Greek varieties appear better adapted to the recent and projected future climate of the region, responding less to warming as compared to international varieties in the majority of the study cases.

The present study is the first attempt in Egypt which focused on determining the development rate of Spodoptera frugiperda at different constant temperatures, the number of degree-days (DD's) required for each stage to complete development, as well as the degree-days required for overall egg-to-adult development. The study was conducted under three constant temperatures (20, 25, and 30 °C at the Department of Zoology, Faculty of Science, South Vally University, Qena Governorate, Egypt. The aim of this study was to determine the development rate of S. frugiperda at different temperatures and to calculate the number of degreedays (DD's) required for each stage to complete its development. The study showed that the mean incubation period was 6.9, 3.4, and 2.1 days at 20, 25, and 30°C, respectively, and the larval duration were 38.5, 23.7, and 18.6 days at the same temperatures, respectively. On the other hand, The average pupal durations were 22.5 at 20, 9.4 at 25, and 7.7days at 30°C. For the adult stage the mean time required for maturation of the ovaries and starting to egg-laying, decreased as the temperature increased, from 4.8 days at 20°C to 2.1 days at 30°C. Meanwhile, the mean duration of generation for S. frugiperda was 72.7, 40.1, and 30.5 days at 20, 25, and 30°C, respectively. The lower threshold of development (t0) and average thermal units in degree-d (dd's) were 15.79 °C and 30.0 dd's for egg stage; 10.39 °C and 360.2 dd's for the larval stage; 14.05 °C and 129.8 dd's for the pupal stage; 12.95 °C and 37.73 dd's for preoviposition period and 12.49°C and 527.3 dd's for a complete generation. The study of heat requirements of the fall armyworm as a new invasive pest came to Egypt from the South Africa countries is very important to determine the thermal heat units for the development and growth of this pest in order to predict the annual field generations in other supplementary studies and draw up a planning IPM strategy for this dangerous pest during the absence of any local information about it. [ABSTRACT FROM AUTHOR]

Blooming in temperate fruit species is triggered by chilling and heat requirements (CR and HR), with a wide range of requirements within the same species. CR for flower bud dormancy release has become a limiting factor for geographical adaptation of fruit trees in warmer regions. The present study investigated the genetic basis of CR and HR to break dormancy and flowering time (FT) in an almond x peach F2 progeny. FT, HR and CR were evaluated over two consecutive years (2015/2016 and 2016/2017). Seven out of the eight identified quantitative trait loci (QTLs) were found in both periods of analysis. They affected eight traits, and included a consistent QTL for breaking dormancy, CR and HR. Two of them, affecting FT and HR for FT (GDHF), colocalized in G1, and the remaining QTLs, affecting chilling and heat requirements, both influenced by dormancy breaking (DB), were located in G6. These results indicate that factors not related to DB affect flowering time in this population. Implications of the results in peach breeding are discussed. [ABSTRACT FROM AUTHOR]

The chilling requirements for dormancy release and heat requirements for flowering were studied for three successive years in eleven Prunus salicina L. cultivars that spanned the range of flowering times in this species. Different methods for estimating chilling requirements were evaluated and compared, and correlations between chilling requirements, heat requirements and flowering date were established. The cultivars examined showed a range of chilling requirements (chill units, CU), spanning from 334.3 CU (‘Pioneer’) to 987.5 CU (‘Songold’). The heat requirements for flowering ranged between 5990 and 9228 growing degree hours. The chilling requirements were significantly different among cultivars, whereas no cultivar effect was found for the heat requirement values. In addition, chill portions were the variable that correlated the most with flowering date in Japanese plum. The dissection of flowering date into chilling and heat requirements indicates that chilling requirements is the main variable driving the variation of flowering time within Japanese plum cultivars. [ABSTRACT FROM AUTHOR]

The use of heat pumps in district heating is one of the most promising technologies for enhancing the efficiency of systems and for meeting the 2030 and 2050 European energy and climate targets. It is essential to assess the available data, the practice and experience of planners and engineers to determine heat pump placement, connection and operational modes in district heating networks, as the systems ought to be capable of covering residential heat requirements for all year around operation. The main selection criteria for the appropriate heat pump system are the heat source, the heat pump technology and the heat requirements. These parameters form a technical triangle, which should be used as a comprehensive instrument to enable heat pump integration into residential district heating. The triangle allows the definition of the bidirectional interdependences and the design of a high efficiency, sustainable heat pump based system. This paper presents the solution to scenarios of how to integrate heat pumps into district heating, in terms of heat pump placement, connection and operational modes based on available heat sources and heat requirement profiles and their environmental impact. [ABSTRACT FROM AUTHOR]

Seedless barberry ( Berberis vulgaris L. var. asperma) is a particular fruit crop that has been used extensively as a medicinal plant in traditional medicine. For the first time, chilling and heat requirements of seedless barberry for breaking of dormancy were calculated. The studied genotypes assayed were selected from Khorasan-e-Jonoobi province in the eastern part of Iran. Uniform one-year-old cuttings were obtained from the shrubs of each genotype after leaf fall and were stored at 4 ± 1 °C for 0.00 (control), 400, 700, 1100 and 1400 h. Six characters including days to the first leaf bud break, days to the first flower bud break, days to full flower bud break, leaf bud number, flower bud number and flowered bunch number were examined. In addition, chilling and heat requirements were determined. Results showed that chilling treatments had significant effects on all the measured traits. The cuttings reached a period of chilling of 1100–1400 h showed the earliest full flower bud break. The highest number of flowered bunches was observed in the cuttings treated with 1400 h chilling. All the genotypes had a chilling requirement of 1400 h. On the contrary, the genotypes were classified into two groups based on heat requirements with 2904 and 3432 growing degree hours (GDHs), however, they were not significantly differed in this regards. In conclusion, the present information can be used to advise seedless barberry farmers about which genotypes are best suited to areas with different winter conditions. [ABSTRACT FROM AUTHOR]

Blooming time is an essential trait in almond cultivars, mainly because of the occurrence of frosts during bloom and early fruit development, when the flowers and the young fruits are very sensitive to freezing temperatures. Traditional almond growing has been mostly restricted to coastal regions where the risk of frosts was minimal or nil, but at present it is shifting to two very different environments: inland regions with high frost incidence and subtropical regions with very low chilling accumulation. Therefore, the chilling and heat requirements for almond blooming have acquired the highest interest when describing a new cultivar and, as a consequence, these requirements have been analysed in this review, as well as the genetics of blooming time as a basis for defining late bloom as an objective in breeding programmes or not. Additionally, the breeding efforts directed to obtain later blooming cultivars have been reviewed, stating that no breeding has been yet undertaken towards earlier bloom because many traditional cultivars were early blooming. Almond breeding has been highly effective in obtaining very late blooming cultivars, well adapted to growing regions with high frost risks, but these very late blooming releases may conversely show adaptation problems in low chilling regions. [ABSTRACT FROM AUTHOR]

Chilling requirements of temperate fruit species may vary substantially depending on the climatic conditions where they grow. In addition, in a climate change context, a precise knowledge of these requirements and their effect on productivity is critical for choosing the best suited cultivars to assure long-term adaptation under low-chill environments. To date most studies circumvented the analysis of productivity when assessing chilling requirements in different climatic conditions. Thus, the chilling and heat requirements of different sweet cherry cultivars ( Prunus avium L.) for breaking dormancy, flowering and fruit set were investigated in two contrasted growing areas in Tunisia: Ain-Drahem (800 m above sea level) and Tibar (328 m above sea level). Additionally, we evaluated several parameters to assess the productivity under these two different conditions. Low chill cultivars showed a higher fruit set in both locations suggesting a better adaption to warm-winter conditions. This three-year study establishes the basis of sweet cherry adaptation under two contrasted locations in Northern Africa. [ABSTRACT FROM AUTHOR]

The purpose of this work was to study the response of two apple cultivars bred for low chilling environments to artificial chilling accumulation. Two trials were carried out; in experiment one, excised shoots were randomly taken from “Caricia” and “Princesa”, and in experiment two, intact and excised shoots of “Caricia”, “Princesa” and “Gala” (control) were collected. After collection, both shoot types were exposed to artificial chilling accumulation (4.0 ± 0.5°C) from 0 to 1200 chill units (CU). Bud break of mixed buds of “Caricia” and “Princesa” was higher than 50% between 0 CU to 1200 CU, irrespective of shoot type. Bud break of “Gala” mixed buds exceeded 50% only in intact shoots after accumulating 900 CU. The mean time to bud break of “Caricia” and “Princesa” diminished with increasing chilling accumulation and stabilized after ~600 CU, depending on the type of shoot and the year of experimentation. The low-chill apple cultivars tested in this work showed shallow dormancy, but they required moderate cold accumulation (800 – 1150 CU) to fully satisfy their chilling requirements. Thus, although their shallow dormancy makes them suitable for cultivation in chill-deficient environments, they cannot be considered low-chill cultivars.

The purpose of this work was to study the response of two apple cultivars bred for low chilling environments to artificial chilling accumulation. Two trials were carried out; in experiment one, excised shoots were randomly taken from "Caricia" and "Princesa", and in experiment two, intact and excised shoots of "Caricia", "Princesa" and "Gala" (control) were collected. After collection, both shoot types were exposed to artificial chilling accumulation (4.0 ± 0.5°C) from 0 to 1200 chill units (CU). Bud break of mixed buds of "Caricia" and "Princesa" was higher than 50% between 0 CU to 1200 CU, irrespective of shoot type. Bud break of "Gala" mixed buds exceeded 50% only in intact shoots after accumulating 900 CU. The mean time to bud break of "Caricia" and "Princesa" diminished with increasing chilling accumulation and stabilized after ~600 CU, depending on the type of shoot and the year of experimentation. The low-chill apple cultivars tested in this work showed shallow dormancy, but they required moderate cold accumulation (800 - 1150 CU) to fully satisfy their chilling requirements. Thus, although their shallow dormancy makes them suitable for cultivation in chill-deficient environments, they cannot be considered low-chill cultivars. [ABSTRACT FROM AUTHOR]

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Chilling and heat requirements for breaking dormancy and flowering were studied in 63 nectarine and 118 peach genotypes ( Prunus persica (L.) Batsch) for seven years. We compared two methods for estimation of requirements and four models for calculation of chill accumulation: Chilling Hours (CH), Chilling Units (CU), Positive Chilling Units (PCU) and Dynamic, while heat accumulations were estimated in growing degree hours (GDH). Additionally, correlations between chilling requirements, heat requirements and flowering date were established. Our results suggest that the Luedeling model is better than the Alonso model to estimate chilling and heat requirements in our field conditions. Moreover, it is recommendable to calculate the chill accumulation in accordance with the Chilling Hours or Positive Utah models. Additionally, since chilling requirements were positively correlated with flowering dates, they seem to be important to regulate blooming in nectarine and peach genotypes. [ABSTRACT FROM AUTHOR]

The main characteristics of the heat accumulation period and the possible existence of different types of biological response to the environment in different populations of olive through the Mediterranean region have been evaluated. Chilling curves to determine the start date of the heat accumulation period were constructed and evaluated. The results allow us to conclude that the northern olive populations have the greatest heat requirements for the development of their floral buds, and they need a period of time longer than olives in others areas to completely satisfy their biothermic requirements. The olive trees located in the warmest winter areas have a faster transition from endogenous to exogenous inhibition once the peak of chilling is met, and they show more rapid floral development. The lower heat requirements are due to better adaptation to warmer regions. Both the threshold temperature and the peak of flowering date are closely related to latitude. Different types of biological responses of olives to the environment were found. The adaptive capacity shown by the olive tree should be considered as a useful tool with which to study the effects of global climatic change on agro-ecosystems. [ABSTRACT FROM AUTHOR]

Heat requirements for grapevine varieties have been widely used to characterize potential growing regions for viticulture. One of the most common landscape classifications is based on the Winkler Index (WI) values, defined as the total summation of daily average air temperature above 10 ^\circ\C from April 1 to October 31 in the Northern Hemisphere. Mapping WI is commonly performed by spatial interpolation of temperature data collected with weather station (WS) networks. However, in complex terrain such as the European Alps, these are usually irregularly and sparsely distributed or unavailable. This renders traditional geospatial interpolation approaches unreliable. As an alternative, thermal remote sensing data, which are intrinsically spatialized, can be used. The aims of this paper are the following: 1) to provide time series of WI-value maps from 2003 to 2010, by means of the Moderate-resolution Imaging Spectroradiometer (MODIS) land surface temperature (MOD11A1 and MYD11A1) daily data and 2) to calibrate them using ground truth data, collected by two WS networks, 3) leading to a classification of the study area into WI regions. WI values from WS data and from MODIS data exhibit a strong linear regression, close to the 1 : 1 prediction with an offset of 42.02 and a slope of 0.90. These coefficients have been used to calibrate the original map, before the following classification. The study area was found to have growing degree days that correspond to four Winkler Regions. The use of MODIS data represents a robust and straightforward method for selectively detecting areas suitable for grapevine varieties, particularly in regions with sparsely distributed WSs. [ABSTRACT FROM PUBLISHER]

Ants (Hymenoptera: Formicidae) are known to be a thermophilic group with fewer species at higher latitudes. They are ubiquitous in the sub-boreal forests of west-central British Columbia (Canada) in the early seral ages of forest succession, nesting almost exclusively in woody debris. Individual species begin to disappear with advancing seral ages as the canopy closes, suggesting the hypothesis that heat gain from insolation is critical to many species. We experimentally manipulated shading of two wood-nesting ant species - Leptothorax muscorum (Nylander) and Formica aserva Forel - to emulate advancing seral age, in an environment documented to support their normal habitation. Shaded down woody debris (DWD) was found to be ca. 2 °C cooler than unshaded DWD, whereas stumps were ca. 1.5 °C cooler when shaded than when unshaded. We found significantly fewer colonies of both L. muscorum and F. aserva in shaded wood, as compared to unshaded, in a pattern consistent with how each species has been observed to respond to advancing seral age. Temperature monitoring during the experiment indicated that soil was cooler than either stumps or DWD, possibly explaining the absence of soil-nesting ant species in these forests. The species-specific differences in ant colony abundance in response to small temperature differences, found in this study, support other research on the significance of temperature in structuring ant assemblages. [ABSTRACT FROM AUTHOR]

The chilling and heat requirements and flowering time were studied, for 2 years, in an almond progeny from the cross between the late-flowering French selection 'R1000' and the early-flowering Spanish 'Desmayo Largueta'. These three temperature-dependent traits showed quantitative inheritance, although for chilling requirements and flowering time a major gene could be involved, modified by other minor genes. The results indicate that flowering time is mainly a consequence of the chilling requirements; heat requirements having a smaller effect. In agreement with the genetic findings, a significant Quantitative Trait Loci (QTL) for chilling requirements was found in G4 together with other minor QTLs in G1, G3, and G7. For heat requirements, two QTLs in G2 and G7 were identified. The results also show the high influence of temperature in the expression of the three traits and their QTL analyses. In addition, QTL analysis for flowering time allowed the identification of one significant QTL in linkage group 4 (G4) that explained most of the phenotypic variation together with other minor QTLs located in G1, G6, and G7. [ABSTRACT FROM AUTHOR]

Abstract: The efficiency of different temperature cycles in inducing budburst of one-year-old shoots of the apricot cultivar ‘Palsteyn’ from dormancy was evaluated. Three replications of shoots were collected during two consecutive years from adult trees, following the accumulation of different amounts of chilling in the field. Thereafter, shoots were exposed to different temperature cycles in growth chambers, for 60 days. The temperature treatments included a continuous temperature of 5°C; daily temperature cycles of 19/5h at 5/15°C, at 5/20°C, and at 5/25°C; and the same temperature cycles for the remainder of the 60-day period, after pretreatment at 5°C for 30 or 45 days. After the temperature treatments, shoots were forced at 25°C until budburst. The mean time to budburst (MTB) (in days) of lateral vegetative, terminal vegetative and reproductive buds was evaluated. The efficiency of the different treatments was greatly influenced by the date on which shoots were cut. High temperatures had a more positive effect on the reduction of MTB when chilling accumulation had occurred in the field instead of the growth chamber. After partial chilling accumulation in the field, high temperatures (25°C) combined with low temperatures are more efficient than cycles of moderate temperatures (15 or 20°C) to induce an earlier budburst. In view of these results, a parallel accumulation of both chilling and heat requirements after partial chilling accumulation is suggested. The application of these results could assist in the development of more accurate models for the prediction of the overcoming of dormancy and blooming. [Copyright &y& Elsevier]

Abstract: Chilling requirements for breaking of dormancy and heat requirements for flowering were studied for 3 successive years in 10 apricot cultivars which spanned the range of flowering times in this species. Different methods for estimating chilling requirements were evaluated and compared, and correlations between chilling requirements, heat requirements and flowering date were established. The cultivars examined showed a range of chilling requirements (chill units, CU), between 596CU (Currot) and 1266CU (Orange Red), though most of them showed chilling requirements between 800 and 1200CU. The results obtained in different years by the Utah and Dynamic models were more homogeneous with respect to the hours below 7°C model. The heat requirements for flowering ranged between 4078 and 5879 growing degree hours (GDH). The apricot cultivars showed important differences concerning flowering date, and the results indicate a high positive correlation between chilling requirements and flowering date, as well as a negative correlation between chilling requirements for breaking of dormancy and heat requirements for flowering. [Copyright &y& Elsevier]

The aim of the present study was to compare the accuracy and reproducibility of six statistical models for the calculation of olive ( Olea europeae L.) heat requirements to trigger the onset of flowering in three Portuguese regions: Reguengos de Monsaraz, Valença do Douro, and Braga. Other aims were to ascertain the date on which the heat-accumulation period started and the threshold temperatures above which the development of reproductive structures starts in olives. The starting and peak dates for the regional O. europeae flowering season were estimated by monitoring airborne pollen from 1998 to 2004 using “Cour” type samplers. The threshold temperature values calculated for the three regions were very similar (9.0 °C for Valença do Douro, 9.2 °C for Reguengos de Monsaraz, and 9.7 °C for Braga). The accumulated daily mean temperature model had less interannual and inter-regional variation, showing best predictive results for 2004, with absolute differences between the observed and predicted dates of 4 d in Reguengos de Monsaraz and 2 d in Valença do Douro and Braga for the onset of flowering date and of 2 d in Reguengos de Monsaraz, 7 d in Valença do Douro, and 4 d in Braga for peak flowering dates. This model was the most accurate, reproducible, and operational to calculate heat requirements for olives to flower, with an average mean temperature accumulation of 1 446 °C in Reguengos, 1 642 °C in Valença do Douro, and 1 703 °C in Braga to reach the onset of flowering. The best initial date for this accumulation was 1 January. (Managing editor: Wei Wang) [ABSTRACT FROM AUTHOR]

Seed dormancy affects germination and subsequent seedling growth in many plant species. In this work the effect of temperature (cold and heat treatments), flowering time of genotypes, and hardness of endocarp on the break of seed dormancy in four almond cultivars, including a broad range of flowering dates, was studied. Mature seeds, with and without endocarp, were stratified at 7 °C for 1–10 weeks, followed by 5 weeks at 22 °C. The number of germinated seeds were recorded weekly for each cultivar, and cold and heat treatments. Despite the great variability observed within cultivars, a relationship between chilling requirements of cultivars for flowering and stratification requirements of seeds for germination was observed. With endocarp, stratification time required to overcome seed dormancy ranged between 6 (early flowering cultivars Desmayo Largueta and Ramillete) and 8 weeks (late-flowering cultivars Mono and Wawona) on average. Elimination of the endocarp reduced the period of stratification needed for germination in hard-shelled cultivars by 3 weeks. This effect was less important in soft-shelled almonds. No important differences between cultivars were observed for heat requirements. Two weeks at 22 °C was enough to reach the higher germination percentage after each cold treatment. [Copyright &y& Elsevier]

The heating requirements of the thermophilic anaerobic digestion process were studied. Biogas production was studied in laboratory experiments at retention times from 1 to 10 days. The data gathered in the experiments was then used to perform a heat and energy analysis. The source of heat was a conventional CHP unit system. The results showed that thermophilic digestion is much faster than mesophilic digestion and therefore produces more biogas in a shorter time or at smaller digester volumes. The major part of the heating requirements consisted of sludge heating. The heat losses of the digester were only 2–8% of the sludge heating requirements. The heating requirements in thermophilic digestion are about twice those of mesophilic digestion. Therefore a CHP unit system cannot cover all of the needs for successful operation of thermophilic digestion. Heat regeneration was introduced as a solution. Heat is regenerated from the sludge outflow at a temperature of 50–55 °C and transferred to the cold inflow sludge at a temperature of 11 °C. Enough heat is regenerated in a conventional counter flow heat exchanger to bring the thermophilic process to the same level as the mesophilic one. Considering the smaller digester volumes and the relatively small investment in the regenerative equipment, the construction of thermophilic digestion systems may be a very good alternative to conventional mesophilic sludge digestion systems. [Copyright &y& Elsevier]

• Two relevant periods controlling almond flowering were evinced, using PLS regression. • Temperature increase during chilling period could delay flowering dates in almond. • A good fit of data was obtained using PLS regression to predict almond dormancy phases. Determining the flowering and the dormancy phases in fruit trees is a crucial process because of their substantial role in some agricultural practices and crop managements. However, few of these studies were conducted on almond flowering and dormancy, particularly in mild climate areas. This study aimed to simulate the dormancy phases, closely involved in the determination of flowering time of almond species in response to temperature variations. To reach this objective, Partial Least Squares analysis was used. In this regard, climatic and flowering data were collected from Ain Taoudjate in Morocco during the period from 1974 to 2014. In fact, a significant temperature increase was highlighted, inducing a decrease in amounts of chill during the studied period. Using Partial Least Squares analysis, a good fit of data was obtained, particularly using mean and maximal temperatures. Two relevant periods controlling the flowering process were highlighted in Tuono cultivar, in concordance with the sequential model in prediction of flowering times. The first long chilling period started from October 01st to January 11th. During this period, temperatures correlated positively with flowering dates, inducing consequently a delayed flowering dates because of low and slow accumulation of chilling requirements. However, the second short forcing period extended from January 18th to March 09th, during which flowering dates were negatively correlated with temperatures. In fact, the accumulation of certain threshold of Growing Degree Hours and Chill Portions during the two periods respectively could delay flowering, particularly in the context of chilling privation in the coming future, causing a serious problem for fruit trees. Significantly, temperatures during the chilling period seemed to affect effectively the flowering dates of almond than temperatures during the forcing period. In this investigation, we demonstrated that Partial Least Squares showed a good fit in explanation of the flowering process and can be used for prediction of dormancy phases and flowering process. [ABSTRACT FROM AUTHOR]