Thermal Time Requirements Research Articles

Seed size dimorphism and environmental factors govern the phenological variations in invasive plant Hyptis suaveolens

Persistent intra-individual variations, although understudied, may explain the population- and community-level ecological patterns of plant species. However, there is a lack of studies investigating the intra-individual phenological variations of a species under the influence of seed size dimorphism, especially in the case of invasive plant species. Therefore, a study was conducted to assess the phenological changes in plants grown from dimorphic seeds (small and large) produced within the persistent calyces of the invasive plant Hyptis suaveolens. Furthermore, the impact of various environmental factors (temperature, thermal time, photoperiod, and relative humidity) on the phenological events of plants grown from both seed classes was also analyzed. In this study, the duration and performance (%) of three phenological events—leaf emergence, flowering, and seed formation—were documented throughout the plant's life cycle (from July 2019 to February 2020). It was observed that all the phenological events lasted longer in plants of the large seed class compared to those of the small seed class. While leaf emergence began and ended on nearly similar days for plants of both seed classes, an earlier occurrence of flowering and seed formation events was observed for plants of the small seed class. The plants grown from small-sized seeds also exhibited lower thermal time requirements, greater photoperiodic requirements, and higher temperature requirements for flowering. The study concludes that phenology in H. suaveolens is influenced by both seed size dimorphism and varying environmental factors, resulting in phenological adaptability and subsequent spread over space and time, which may contribute to increased invasiveness of the species.

Phenological description and thermal time requirements for the seedling phase of three Brazilian native forest species

AbstractUnderstanding the phenological stages and thermal requirements of the seedling phase of forest species is crucial for sustainable nursery management. This study proposed an adaptation of a phenological scale based on the basic Biologische Bundesanstalt, Bundessortenamt, and Chemical industry, associated with the thermal requirement to describe the phenological stages during the seedling phase of three forest species: Cybistax antisyphilitica, Libidibia ferrea, and Platycyamus regnellii. The phenological scale of C. antisyphilitica and L. ferrea was defined and described through 22 seedling development stages ranging from dry seed to 20th visible leaf emitted on the main stem (from 00 to 120) and P. regnellii for 12 leaf development stages, from dry seed to 10th visible leaf emitted on the main stem (from 00 to 110). In addition, the duration (days) and thermal time (°C day) were determined for each seedling development stage. C. antisyphilitica needs to accumulate more energy (and days) to finish the seedling phase (1551.9°C day or 261 days) compared to L. ferrea (1127°C day or 175 days) and P. regnellii (1109.7°C day or 193 days). However, the three forest species exhibit similar energy demands throughout most stages of seedling development, except code 09–12 for C. antisyphilitica. This study provides important information for optimizing silvicultural techniques, evaluating the response of temperature on phenological stages, and assessing the impacts of global warming on forest seedling development.

Microclimatic influence on thermal time requirement, growth dynamics and yield attributes of cotton in the South-Western region Of Punjab

Microclimatic influence on thermal time requirement, growth dynamics and yield attributes of cotton in the South-Western region Of Punjab

Seed dormancy and germination characteristics of Osteomeles schwerinae, a riparian plant endemic to the Hengduan Mountains and adjacent regions

Osteomeles schwerinae, an endemic plant with ecological restoration functions from the hot/warm-dry river valleys of the Hengduan Mountains and adjacent regions, has low seed germination in cultivation. This study attempted to improve seed germination by testing the effect of several treatments including dry after-ripening (DAR), GA3, light and temperature treatments for seeds from three populations. DAR increased germination at 25/15°C but not at 15/5°C, as compared with fresh seeds. DAR was sufficient to break dormancy; GA3 could not significantly increase germination percentage, indicating that seeds of O. schwerinae appear to have non-deep physiological dormancy. After the dormancy is broken, temperature significantly affects germination. Seeds germinated significantly better at higher temperatures (20-25°C) than at lower (< 15°C) and extreme high temperatures (> 30°C). A base temperature for germination (Tb) of 4.9-9.3°C and a thermal time requirement for 50% germination (50) ranging from 158.7 to 217.4°Cd were identified for non-dormant DAR seeds, depending on the population. This study provides a theoretical basis for dormancy-break and germination of O. schwerinae seeds.

Temperature Effects on Development of Meloidogyne Enterolobii and M. Floridensis.

Meloidogyne enterolobii and M. floridensis are virulent species that can overcome root-knot nematode resistance in economically important crops. Our objectives were to determine the effects of temperature on the infectivity of second-stage juveniles (J2) of these two species and determine differences in duration and thermal-time requirements (degree-days [DD]) to complete their developmental cycle. Florida isolates of M. enterolobii and M. floridensis were compared to M. incognita race 3. Tomato cv. BHN 589 seedlings following inoculation were placed in growth chambers set at constant temperatures of 25°C, and 30°C, and alternating temperatures of 30°C to 25°C (day–night). Root infection by the three nematode species was higher at 30°C than at 25°C, and intermediate at 30°C to 25°C, with 33%, 15%, and 24% infection rates, respectively. There was no difference, however, in the percentages of J2 that infected roots among species at each temperature. Developmental time from infective J2 to reproductive stage for the three species was shorter at 30°C than at 25°C, and 30°C to 25°C. The shortest time and DD to egg production for the three species were 13 days after inoculation (DAI) and 285.7 DD, respectively. During the experimental timeframe of 29 d, a single generation was completed at 30°C for all three species, whereas only M. floridensis completed a generation at 30°C to 25°C. The number of days and accumulated DD for completing the life cycle (from J2 to J2) were 23 d and 506.9 DD for M. enterolobii, and 25 d and 552.3 DD for M. floridensis and M. incognita, respectively. Exposure to lower (25°C) and intermediate temperatures (30°C to 25°C) decreased root penetration and slowed the developmental cycle of M. enterolobii and M. floridensis compared with 30°C.

Phenological description and thermal time requirement of tamarind (Tamarindus indica) in tropical conditions

AbstractTamarind is one of the highly valued fruit trees of the tropical world. Considering the potential of the crop, a precise standardised description of its growth stages and thermal time requirement were studied to ensure efficient agronomic practices. Phenological growth stages of tamarind are defined according to the BBCH (Biologische Bundesanstalt, Bundessortenamt und Chemische Industrie) scale using a three‐digit numerical system. The phenology of tamarind is characterised by eight principal growth stages: bud growth, leaf growth, shoot growth, inflorescence growth, flower development, fruit growth, fruit maturation and dormancy. Principal growth stages of tamarind are defined and described through 39 secondary growth stages. For each phenological stage, duration and thermal time were also ascertained. It is evident that thermal time for fruit growth and maturation of tamarind is substantially high, whereas inflorescence and leaf require less thermal time to complete their growth. The study could be of great help to tamarind growers and scientists for implementation of efficient agronomic management protocols as well as for assessing the response of critical phenological growth stages to temperature.

Dominant sources of uncertainty in simulating maize adaptation under future climate scenarios in China

CONTEXTThe potential of climate adaptation has been widely investigated with a climate-crop modeling approach. Although different sources of uncertainty in projected crop yields have been quantified in climate change impact assessments, uncertainty in simulating the crop adaptation to future climate has not been fully assessed. OBJECTIVEThe objective of this study was to determine the uncertainty in simulating maize adaptation to future climate change with two adaptation options (adjusting planting date and shifting cultivars) at four contrasting sites across China's Maize Belt. METHODSMaize yield with adaptation was simulated using three crop models (APSIM, DSSAT-CERES, and STICS) driven by 22 global climate models (GCMs) under four emission scenarios of future societal development pathway (SSP126, SSP245, SSP370, and SSP585) during two periods (2040–2069 and 2070–2099). RESULTS AND CONCLUSIONSWe found that late planting had a greater potential to cope with climate change at most study sites. However, all sites required new cultivars with increased thermal time requirements. Under optimum management options at the four study sites, rainfed maize yields were likely to increase by 1.9%–68.3% compared with yields obtained without adaptation. For the adaptation simulation using adjusted planting date alone, GCM was the major source of uncertainty, accounting for 22.9%–36.7% of the total uncertainty at all sites except a high-altitude site where changing planting time was the major source of uncertainty (32.4%). For the adaptation simulation using shifting cultivar alone, crop model was the dominant source of uncertainty, accounting for 24.0%–38.0% of the total uncertainty at all sites except a high-latitude site where shifting cultivar was the major source of uncertainty (34.0%). These findings demonstrated that adaptation options have great potential for increasing maize yields, and the major source of uncertainty depends on study sites and adaptation type used. SIGNIFICANCEThe results of this study advance the understanding of the dominant sources of uncertainty in crop yield under different climate adaptations, thereby improving our confidence in assessments of future climate impact on maize yields determined by different adaptation strategies.

Thermal time requirement and heat use efficiency in wheat crop in Bihar

Thermal time requirement and heat use efficiency in wheat crop in Bihar

Acai palm base temperatures and thermal time requirements in eastern Amazon

Abstract The objective of this work was to deter mine the base temperatures, thermal time requirements, and length of the main reproductive growth stages of acai palm (Euterpe oleracea) in the northeast of the state of Pará, in eastern Amazon, Brazil. The experiment was carried out from 2017 to 2019 in a 10 ha acai plantation, using the time-series analysis. Plant phenology was monitored weekly, and local weather conditions were monitored daily. The lower and upper base temperatures were of 12.92 and 32.46°C, respectively, for pre-flowering; 13.50 and 32.23°C for flowering; 12.14 and 32.55°C for green fruit stage; 11.64 and 32.78°C for fruit color-changing stage; and 11.23 and 32.94°C for maturation. The thermal time requirement and the average cycle length for the ideal harvest time of acai palm were 3,893.15 degree-days and 283 days, respectively. The thermal time requirement and the duration of the reproductive growth stage for acai palm are influenced by the period of the year and the variability of air temperature, which, when high, reduces the cycle of the crop, and when mild, increases it.

Effect of sowing date, irrigation and mulch on thermal time requirement and heat use efficiency of maize (Zea mays L.)

The field experiments was carried out for three years (2015 to 2017) at the Research Farm, Department of Climate Change and Agricultural Meteorology, Punjab Agricultural University, Ludhiana with maize variety PMH-1 sown on three dates (D1-Third week of May, D2-Second week of June and D3- First week of July) under two irrigation regimes (I1 = IW:CPE 1.0 and I2 IW:CPE 0.75) and mulch application (M1: straw mulch @ 5 tha-1 and M2: without mulch) in a split plot design.Results revealed that the early sown crop(third week of May) took higher number of days and heat units to attain various phenophases. Maize variety PMH-1 consumed maximum heat units of 1952oC days for maturity under early sown condition. The heat use efficiency was highest (3.04 kg ha-1oCday-1)for the crop sown during June. Among irrigation regimes, the HUE was higher (2.89 kg ha-1oC day-1) in IW: CPE = 0.75 level of irrigation ascompared to IW: CPE = 1.00 (2.81 kg ha-1oCday-1) and higher HUE was obtained with mulch application (M1) (2.92 kg ha-1oCday-1) as compared to without mulch (M2) (2.76 kg ha-1oCday-1). The sowing of maize crop during second week of June with irrigation of IW: CPE 0.75 under mulch application have been found to be the most efficient for heat utilisation.

Thermal Time Requirements for Maize Growth in Northeast China and Their Effects on Yield and Water Supply under Climate Change Conditions

Northeast China (NEC) is a region sensitive to climate change. However, the adoption of long-season maize cultivars in NEC has caused a substantial yield increase under climate change conditions. It is important to determine whether such cultivar adoptions are effective throughout the whole NEC to sustainably increase grain yield. In this study, phenological observations and meteorological data at six sites from 1981 to 2018 were used to detect thermal time (TT) trends during the maize growing period. TT, as a parameter for measuring changes in maize cultivars, was used in the crop simulation model CERES-Maize to examine the variations in maize yield produced with different cultivar × climate combinations in different decades. In NEC, both TTs from emergence to anthesis and from anthesis to physiological maturity showed significant increasing trends from 1981 to 2018. Simulation results for humid areas revealed that adopting longer-season cultivars during 2000–2018 caused yield increases, ranging from 6.3% to 13.3%, compared with the 1980s. However, for stations in semi-humid areas, maize grain yield showed a decrease or a small increase (from −12.7% to 8.0%) when longer-season cultivars were adopted during 2000–2018. For semi-humid areas, decreasing trends in the ratios of rainfed yield to no water-stress yield (Yrainfed/Yno water-stress) and lower Yrainfed/Yno water-stress values during 2000–2018 indicated a growing sensitivity of maize production to water, which was attributed to changes in TT and precipitation. Our results indicate that, for the semi-humid area, maize yield was limited by water after introducing cultivars with higher TT requirement under climate change conditions. Therefore, securing food supplies will depend on increases in water-use efficiency levels and other adaptive strategies, such as varietal diversification, drought-resistant varieties, conservation tillage and irrigation.

Evaluating the Effect of Climate Variability on Zea Mays Productivity over Glen Research Station: South Africa

Rainfall and temperature are one of the key environmental parameters that determines the development of a crop and livestock from one growing stage to maturity. Furthermore, temperature is critical beyond maturity but to post harvesting and storage. Rainfall is fundamental in the selection of planting dates, cultivar selection and planting density. Whereas, temperature is essential for calculation of chill and heat units for determining conducive environmental conditions for crop productivity and livestock well-being. In this study, Instat Plus statistical package is utilized to determine potential planting dates, the growing seasons, maize (Zea Mays) for different planting dates from last dekad of October to 1st dekad of January. The growing period length vary from short (less than 100), medium (above 100 days) and long term (above 120 days) varieties. The correct choice of planting time and crop type in the most important decision a farmer or a researcher can make. Taking considerations of water productivity and thermal time requirement for a selected cultivar lessons the effects of high frost risks and water shortages, which leads to soil water deficit and crop wilting but encourage supporting maize growth and development. The study also looks at how heat stress jeopardizes the growth in crops, and further determine crop suitability whether to be early or late in season based on thermal times. A thorough analysis and interpretation of log-term climate data would enable the intermediaries to understand valuable knowledge for improved productivity. This paper analysed a long-term climate (1922-2020) data analysis for Glen automatic weather station, to determine climate variability and climate change possibilities, calculate heat unit and chill units. Further, develop suitable adaptation strategies relating to maize crop.

Thermal requirements and germination niche breadth of Polygonum ferrugineum Wedd. from southeastern Brazil

AbstractTemperature may regulate seed dormancy and germination and determine the geographical distribution of species. The present study investigated the thermal limits for seed germination of Polygonum ferrugineum (Polygonaceae), an aquatic emergent herb distributed throughout tropical and subtropical America. Seed germination responses to light and temperature were evaluated both before (control) and after stratification at 10, 15 and 20°C for 7, 14 and 28 d. Germination of control seeds was ~50% at 10 and 15°C, and they did not germinate from 20 to 30°C. The best stratification treatment was 7 d at 10°C, where seed germination was >76% in the dark for all temperatures, except at 30°C, and < 60% in light conditions. A thermal time approach was applied to the seed germination results. Base temperature (Tb) was 6.3°C for non-dormant seeds and optimal temperature (To) was 20.6°C, ceiling temperature (Tc (<50)) was 32.8°C, and thermal time requirement for 50% germination was 44.4°Cd. We concluded that a fraction of P. ferrugineum seeds is dormant, has a narrow thermal niche to germinate (10 and 15°C) and that cold stratification (10°C) alleviated dormancy and amplified the thermal range permissive for germination of the species. Consequently, P. ferrugineum is expected to occur in colder environments, for example, at high altitudes. Higher temperatures decrease the probabilities of alleviate dormancy and the ability of their seeds to germinate.

Phenological development of subterranean clover cultivars under contrasting environments

AbstractSix subterranean clover cultivars (representing early and late flowering genotypes from three subspecies) were used to describe and quantify their phenological development. The vegetative (V) and reproductive (R) development phases, in response to different environments created by eight sowing dates were quantified. The period from sowing to emergence was constant in thermal time at 110°Cd and the first trifoliate appeared at ~300°Cd. Crops sown in autumn had the longest period from runner initiation until floral bud initiation (R1), which would allow an extended period of grazing, particularly for later flowering cultivars like ‘Denmark’. To maximise seed set (particularly in year 1) a maximum period between R3 and R11 is required (seed set window). This ranged from 319 ± 42.3°Cd for ‘Leura’ to 661 ± 73.1°Cd for ‘Narrikup’. The complete crop life cycle from sowing (V0) to maturity (R11) ranged from 1269 ± 31°Cd (equivalent of 123 ± 6.3 days) for ‘Antas’ sown in July to 2799 ± 47°Cd (300 ± 3.9 days) for ‘Woogenellup’. When sowing occurred in an increasing photoperiod (June–November) the life cycle of all cultivars was 59% shorter than when sown in a decreasing photoperiod. The numeric scale was able to describe all the variation in the phenological phases and could be used to quantify thermal time requirements for specific phenophases. This would allow subterranean clover management to be optimised (husbandry, grazing and seed harvest) at a local level, and provides the basic parameters for inclusion in annual pasture simulation models.

Development of a precise thermal time model for grain filling in barley: A critical assessment of base temperature estimation methods from field-collected data

Precise phenology modelling of grain filling is essential to understand how the environment explored by barley crops in the field affects malting quality. Grain-filling duration is controlled by temperature; hence thermal time models are widely used for describing grain development. Although a precise base temperature is essential for the accuracy of thermal time models, estimations of this parameter for barley grain filling are scarce in the literature; moreover, the methods employed for its determination seldom establish clearly whether grain filling is being treated as a development or as a growth phenomenon. Even worse, the base temperature during grain filling is usually arbitrarily set to zero. In this work we tested five different methods to estimate the thermal time requirement for completing grain filling in four commercial barley cultivars and the base temperature above which temperature must be accumulated for its calculation, using field-collected data. The crops were sown in a wide range of different dates during three consecutive years and grown under two contrasting nitrogen availabilities. All the estimation methods performed relatively well. Developmental base temperature was close to 8 °C for all cultivars, although genotypic differences were noted. Optimum temperatures for grain filling are reported for three of the four cultivars; however, including this parameter in the models only slightly improved the predictions in one out of three cultivars. The effect of nitrogen availability was negligible and inconsistent across cultivars and environments thus indicating that the models developed can be applied in a wide range of nutritional situations. A broad application model, with a base temperature of 8.4 °C and a thermal time requirement for completing grain filling of 352 °Cd, is reported for barley grain development. All the models were validated against independent data. These models can be used by researchers aiming to unscramble the effects of environment explored by the mother plant on grain malting quality. Further applications include predicting the timing of physiological maturity, and with it, harvest time.

Thermal niche for germination and early seedling establishment at the leading edge of two pine species, under a changing climate

Pines are the most popular species for reforestation in Mexico, however reforestation programs have little success due to a high mortality of pine seedlings. Shifts in the distribution range due to climate change has been predicted for many species specially at their distribution borders. Understanding the thermal limits of germination and early seedling growth at the leading edge population in current and future climates could enable the development of suitable propagation practices and conservation strategies. Seeds of Pinus douglasiana and Pinus maximinoi, from their northern distribution range in a temperate sub humid region, were germinated and seedlings were grown across a range of temperatures from 10 to 35 °C. A cardinal temperature model was then employed to obtain the thermal coefficients for seed germination, seedling growth and survival. Projected temperature increase by 2090 according to IPCC scenarios RCP 2.6 and RCP 8.5 were used to predict the germination and early establishment behaviour of both species. Thermal requirements were similar between species and in different developmental stages showing base temperatures of 9.4−10 °C for germination, 9.8 °C for root growth, 9.6 °C for shoot appearance and 8.4 °C for shoot growth; and thermal time requirements of 65−69 °C d for germination, 107 °C d for root growth, 103−107 °C d for shoot appearance and 140−141 °Cd for shoot growth. However, seedling survival was higher at 20 and 25 °C. Different sensitivities to low temperatures for germination and seedling establishment could be factors that drive ecological divergence between these species and explain their altitudinal tolerances. As timing of germination and seedling growth are expected to be accelerated under climate change scenarios, seedling establishment and survival in both species could be altered .

Quantification of Climate Warming and Crop Management Impacts on Phenology of Pulses-Based Cropping Systems

Climate warming is impacting the phenology, growth and productivity of diverse cropping systems at local, regional and global levels. Long-term observed chickpea-mungbean system (CMS) phenological changes were used for the determination of the relationship between crop practices, climate warming and phenology for the making strategies for CMS to minimize negative climate change impacts. Observed thermal trend from sowing to maturity was ranging from 0.82 to 1.15 °C decade−1 for chickpea and 0.64 to 0.97 °C decade−1 for mungbean during 1980–2018. Observed chickpea phenology stages was earlier for mean value of 7.04 (sowing; S), 6.76 (emergence; E), 4.31 (anthesis; A), 2.15 (maturity; M) days decade−1, whereas chickpea phases were decreased averagely 2.73 (S–A), 2.16 (A–M), 4.89 (S–M) days decade−1. Mungbean, ‘S’ 6.24, ‘E’ 5.97, ‘A’ 3.76, and ‘M’ 2.01 days decade−1 were occurred earlier. Period of mungbean phenology phases were lessened with averaged 2.45 (S–A), 1.76 (S–M) and 4.23 (A–M) days decade−1, respectively. Phenological stages and phases of both crops chickpea and mungbean correlated negatively with rising temperatures at all sites studied. By using CROPGRO-Chickpea and CROPGRO-Legume models for usual chickpea and mungbean cultivars at the sites for 38 years duration indicated that model predicted phenology stages were accelerated with thermal trend more as compared with observed stages. This showed that, during last decades, growing newly evolved cultivars of pulses having more thermal time requirement have significantly offset the increased temperature induced changes in chickpea (33%) and mungbean (20%) phenology. Therefore, for the mitigation of climate warming influences, newly evolved cultivars for CMS must be familiarized that need greater demand for degree days and having higher tolerance to temperature.

Reproductive development in subterranean clover (Trifolium subterraneum L.): A reanalysis of Oceania datasets

Abstract Quantification of thermal time requirements for flowering in subterranean clover is vital to inform cultivar choice on farm, management strategies and for predictive purposes in biophysical models. As an annual crop, the viability of subterranean clover relies on its ability to regenerate by reaching flowering and setting seeds to establish the crop in the following growth season. This study reanalysed published datasets on flowering time of subterranean clover to estimate thermal-time requirements, considering interactions between genotypes and environmental aspects (temperature and photoperiod). Fifteen peer-reviewed publications from New Zealand and Australia were used that included 369 independent data points from 1955 to 2000. The estimated time from sowing to flowering ranged from 44 to 271 days or 628–2600 °C d. Temperature was the main driver of flowering, but photoperiodism influenced subterranean clover reproductive development. There was a strong hysteresis in the relationship between time to flower and photoperiod (Pp), depending on the Pp direction (increasing or decreasing Pp). Explanatory functions in response to photoperiod value and direction were estimated for different genotypes (“early” and “late”-cycle cultivar groups). There was a strong seasonality explained by a total requirement of 1090 ± 94.8 °Cd or 740 ± 79.8 °Cd for late and early cultivars in an increasing photoperiod. In a decreasing photoperiod the thermal time target increased at a rate of 977 ± 90.9 °Cd/h and 834 ± 68.7 °Cd/h for late and early cultivars, respectively.

Thaumatococcus daniellii phenology and growing degree day requirements under different irradiance and fertiliser levels

AbstractThaumatococcus daniellii is a rhizomatous monocotyledonous, perennial herb species of the Marantaceae family. The fruit aril contains thaumatin, a sweet protein with sweetness intensity that is about 1,600–3,000 times that of sucrose and is extensively employed as a natural sweetener. The species has potential as an imperative economic crop if cultivated under proper agronomic practices. Phenological development and thermal time requirements are critical to ensuring a high yield. The aim of this study was to determine the phenological stages according to the BBCH scale and growing degree days (GDDs) under different irradiance and fertiliser levels. Seedlings were raised from rhizomes and grown on the field using a randomised complete block design with four treatments and three replications. The study was carried out at the Botanical Garden, Shah Alam, Malaysia, from July 2014 to February 2017. The treatments consisted of combinations of two irradiance and two fertiliser levels, which were designated as high irradiance with either low (T1) or high fertiliser (T2) and low irradiance with either low (T3) or high fertiliser (T4). A detailed phenological development using two‐ and three‐digit coding systems was conducted on 12 clumps (one clump/replicate/treatment). The species has eight principal stages, which include bud and leaf development, formation of side tillering, petiole elongation, emergence of synflorescence, flowering, fruit development and fruit maturity. Both irradiance and fertiliser levels affected certain phenological stages; with leaf, tiller, synflorescence and fruit strongly influenced by irradiance levels. Leaf growth was more vigorous under high irradiances compared with low irradiances and took about 36 to 42 days to attain full maturity. The clump growth or size is a function of tiller numbers. The tiller number increased with increase in clump age. The onset of certain phenological stages was associated with clump age. The clumps commenced production of synflorescence when tiller number was in the range of 30 to 40, and started fruit formation when tiller number reached 70. Both events occurred under a combination treatment of high irradiance with high fertiliser. The GDD requirement of any phenological stage or development of any plant part is contingent upon the duration of a particular stage or process, as measured in days after emergence or transplanting. The longer the duration, the higher the GDD and it varies with treatments. The total GDD required for the completion of the single leaf growth ranged from 852 to 1,022°C, while the emergence of synflorescence under high irradiance occurred with GDD of 5621 (T2) and low irradiance at 9387°C (T3). Fruit formation was observed only under high irradiance with GDD ranging from 9030 (T2) to 13,147°C (T1) during the study period. A description of phenological development according to BBCH scale and GDD requirements in response to differences in irradiance and fertiliser is imperative. It provides a detailed knowledge based on T. daniellii development vis‐à‐vis growth and environmental requirements. This will pave the way for attainment of an efficient crop agronomic practice.

Phenological behavior of feijoa accessions in their main diversity center

Abstract: The objective of this work was to identify the minimum base temperature (Tb) and the maximum base temperature (TB) to predict the thermal time for six phenological stages of feijoa (Acca sellowiana) accessions. During ten noncontinuous harvests (2004 to 2017), 247 feijoa accessions, maintained in the Feijoa Active Germplasm Bank, in São Joaquim, in the state of Santa Catarina, Brazil, had their data recorded for: initial sprouting (IS), initial flowering (IF), end of flowering (EF), beginning of harvest (BH), and end of harvest (EH). Tb and TB were estimated by the Arnold’s method of least variability, and the TT requirements were obtained by Ometto’s method. Tb at 7.76°C and TB at 17.0°C were necessary when feijoa plants started growing (IS stage) just after winter; and Tb at 10.6°C and TB at 19.5°C were the calculated values from IS until BH. The budding stage of the accessions began in the mid-September (50.6%); flowering occurred predominantly in November (90%); and harvest began in March and lasted until May. About 176 days, with 1,014.4 growing degree-days, are necessary to complete the productive cycle from IS until BH. The early, intermediary, and late fruit-ripening accessions show different thermal time requirements.