جستجوی مقالات مرتبط با کلیدواژه « Growing degree day » در نشریات گروه « کشاورزی »

In order to evaluate the effects of planting date and plant density on phenology, seed yield, and essential oil quality of Guar, an experiment has been conducted during 2018-2019 and 2019-2020 growing seasons. It is a split plot layout based on a randomized complete block design with three replications. Different planting dates are considered as the main factor, including September 5th to February 5th as monthly. Three plant densities are considered as sub-factor (20, 40, and 60 plants in a square meter). The required growing degree- day (GDD) from sowing to physiological maturity ranges between 1802.3 and 2347.9 °d on different planting dates. The highest GDD from sowing to physiological maturity is observed on May 5th. The highest seed yield (3780 kg / ha) and galactomannan yield (1050 kg / ha), 100- seed weight (3.5 g), and oil percentage (17.9%) belong to May 5th + 40 plants per m2. by delaying planting time, 100- seed weight causes oil percentage to drop and the seed yield (40%), galactomannan (68%) and the oil percentage (15%) are observed in September.  Therefore, it seems that the best time and density for planting Alyssum is May 5th with a density of 40 plants per m2.

Canada thistle (Cirsium arvense L.( occurs in pastures and wheat fields and is common in most provinces, where it is considered a major agricultural weed in Iran. Increasing our understanding of the environmental factors that determine Canada thistle emergence can provide strategies to control it. Therefore, in this paper the morphological characteristics of 10 ecotypes collected from different regions of Iran and the effect of temperature on the percentage and rate of emergence of root buds in controlled conditions were investigated. Temperature was considered as the treatment because it is one of the most important factors that fluctuate between the diffusion regions in Iran.

To evaluate any morphological differences among ecotypes of Canada thistle, root fragments were collected from 10 provinces of Iran in 2020. To reduce the effect of the environment, the roots were propagated again in pots in the greenhouse under controlled conditions. Day and night temperatures were 30 and 15 °C, respectively. The root pieces were then harvested and stored at 5 °C for 3 months. Two 10 cm long roots with same weight and same number of buds were planted in pots containing loamy sandy soil. The pots were irrigated during the experiment and the plants were not exposed to water stress. A Completely Randomized Design was conducted at Science Research Branch, Islamic Azad University. After 70 days plants were harvested. The numbers of leaves and branches on the main shoot and number of capitulum were counted and the root length, height of the main shoot and capitulum length were measured. Data analysis of variance was performed using SAS software and means were compared using protected LSD test. Cluster analysis was performed by calculating the Euclidean distance for grouping populations using SPSS software and its dendrogram was drawn. The root and shoot dry weights were measured after drying at 70 °C for 48 h after harvest. At second experiment, temperatures 1- 38° C were evaluated for studying the effect of temperature on percent and rate of shoot emergence. Base temperature (temperature at which the germination rate is zero) was obtained using the linear regression equation between germination rate and temperature.

There were significant differences at morphological traits among Canada thistle ecotypes except capitulum length. Root dry weight varied from 8 g in Gonbad ecotype to 11.5 g in Varamin ecotype. Total dry weight was the lowest in Hamedan and was not significantly different from Mashhad and Gonbad ecotypes. The highest total dry weight belonged to Shiraz ecotype. Cluster analysis grouped 10 ecotypes at four groups. First group consisted of Babol, Gonbad and Moghan ecotypes. Varamin, Shahreza, Mashhad, Hamedan and Shiraz placed at second group. Kermanshah and Dezful were placed at third and fourth groups, respectively. In the next step, the data were correlated into principal components on the correlation matrix. In total, the three main components explained about 80.20% of the total data changes. The first component explained 34.33% of the changes. Main stem height, total dry weight and number of leaves had a positive correlation with this component and shoot dry weight had a negative correlation with it. The second component explained 33.82% of the changes in the total data. Groundwater dry weight and total stem + root length had high coefficients in this component. The third component accounted for 12.03% of the changes, with only the number of capitols in each branch having a high positive correlation with this component. The estimated base temperatures for the emergence of bud root were 5.34, 4.91, 5.98, 5.70, 4.42, 6.52, 3.12, 6.26, 3.80 and 5.91°C for Babol, Varamin, Shahreza, Gonbad, Mashhad, Dezful, Kermanshah, Moghan, Hamedan and Shiraz ecotypes, respectively. Emergence growth degree day for Babol, Varamin, Shahreza, Gonbad, Mashhad, Dezful, Kermanshah, Moghan, Hamedan and Shiraz were 201, 210, 200, 205, 190, 220, 182, 202, 190 and 210, respectively.

Temperature had a significant influence on the root of Canada thistle. When the temperature was below 3°C, no emergence occurred. Temperature affected not only the percentage of emergence but also the emergence rate. There was a significant linear relationship between the emergence rate and incubation temperature. High temperature probably causes activation of the enzymatic and physiological function of root buds and increases the rate of mobilization of nutrient reserves to the growing belowground shoots.

One of the important factors in the adaptation of plants to new environmental conditions is the appropriate response of development stages to temperature and photoperiod regimes. The thermal time, growing degree days (GDD) or heat unit concept is commonly the basis for modeling phenological development in crop models for different common crops and under-utilized crops. The GDD concept describes crop development as a function of temperature accumulation above the base temperature (lower limit) and in some cases below a cut off temperature (upper limit). Evaluation of plant photoperiod sensitivity is often beneficial help to use appropriate cultivars which in turn to ensure cultivation success. Considering that adaptation of quinoa to new regions demands acclimation to appropriate temperature range also day-length, this study aimed to investigation of quinoa response to Yazd weather condition as an arid region to assess the possibility of quinoa cultivation under these conditions.

This research was conducted through 10 separate experiments and were based on a randomized complete block design with three replications. The experimental treatment consisted of five lines (1, 2, 3, 4 and 5), and one cultivar (Titikaka) which belong to different maturing groups including early, middle and late maturing. Ten planting dates selected to be serial as following: March 29, April 29, May 28, June 28, July 26, August 23, September 6, September 20, January 29, and February 29. Every three days, phenological stages of each line including planting distance to each stage of development including emergence, four leaves, flower bud, panicle formation, pollination, seed filling, seed hardening and ripening were recorded accordingly. Using local weather data and equation 1 the needed GDD for every development stage was calculated:GDD= (Tmax-Tmin)/2-T(1)MS-Excel Ver. 15 was employed to arrange recorded data and required calculating. Fitting equations and plotting the graphs were done using Slide Write Ver. 2 and Minitab Ver. 20 software.  

The results showed that the mean of flowering temperature up to seed formation stage was between 25 and 30 °C for five lines and was between 20 and 25 °C in cultivar 6. The mean length of photoperiod for flowering and seed formation stage of these lines was between 12 and 12.5 hours. The relationship between temperature and day length was inversely related to the number of days of flowering stage, i.e., with decreasing day length and increasing temperature, the number of days for flowering stage was increased. The time required for flowering stage, between 20 to 30° C, for the early maturing cultivar was about 35 days, for the middle maturing lines including 1, 2, 3 and 6 was about 40 days and for the late maturing line 4 was about 45 days. At temperatures higher than 30 °C, a decreasing trend was observed in the number of days required for flowering stage. From the budding stage to the end of the growth period, a significant difference in the GDD was observed for the quinoa lines. The GDD of quinoa was the highest (2530 °C) for late maturing line (4) and was the lowest (1805 °C) for the early maturing cultivar. The effect of planting date on the GDD of quinoa lines showed that moving from March planting date to July, there was an increasing trend on the GDD of quinoa lines and by moving from July planting date to October, a decreasing trend was observed.

In general, quinoa is a short-day plant which is affected by the day length from flowering to seed maturity stages. Line 6 responded qualitatively to day length; however, the other lines responses were quantitatively. The study of the simultaneous effect of temperature and day length showed that temperature has a compensatory effect for day length during flowering stage. According to the results, it seems that the most suitable planting date for early lines suggests in September, for middle maturing lines suggests in August and for late maturing lines suggests in August. The results also showed that line 6 is more suitable than other lines for cultivation in cold regions.

The present study has been conducted to investigate the duration of growth period of different cannabis (Cannabis sativa L.) ecotypes and their responses to water stress based on a factorial completely randomized experiment design in the greenhouse condition at the University of Tehran in 2017. Irrigation levels include 50%, 75%, and 100% of field capacity, with the ecotypes being Urmia, Sanandaj, Tabriz, Dasht-e-Moghan, Rasht, Khomein, Daran, Qom, Shahroud, Kerman, Tabas, and Saravan. Results show that Rasht and Khomein ecotypes have had the highest and lowest duration of germination phase and growth degree-days (GDD1), respectively. The highest duration of vegetative, flowering and maturation phases belong to Dasht-e-Moghan, Rasht, and Dasht-e-Moghan ecotypes with 71.33, 30, and 46.66 (days), respectively, at 100% field capacity. The lowest durations of these phases could be seen in Tabas, Tabriz, and Saravan ecotypes with 42, 16, and 17 (days), respectively, at 50% field capacity. Also, the highest values of growth degree-days for vegetative (GDD2), flowering (GDD3), and maturation (GDD4) phases  for Dasht-e-Moghan, Kerman, and Dasht-e-Moghan ecotypes with 1788, 836, and 1169 (0C.d), respectively, at 100% field capacity, with their lowest values belonging to Tabas, Tabri,z and Saravan with 1039, 413, and 448 (0C.d), respectively, at 50% field capacity. Based on growth period duration and cumulative growth degree-days (total GDD), Tabas and Dasht-e-Moghan ecotypes are found as earliest and latest ecotypes, respectively.

The present study was carried out to compare the phenology of annual ground cherry (Physalis divdricata L.) and its effect on maize yield ‎ ‎.

A field experiment was conducted in the Research Station of Mahidasht in Kermanshah Agricultural and Natural ‎Resources Research and Education Center, in 2017.‎ Different densities of annual ground cherry, including 0, 8 and 16 plants m-2 and corn were planted.  The competition‎ and their phenological stages ‎were recorded based on GDD (growing degree days) for each growing stage. ‎

The results of this study showed that ‎annual ground cherry ends its phenological stages later than corn. In order to complete its life cycle, ‎‎1262.7 growing degree days and 159 days were needed. Thus, complete life cycle of corn required ‎‎1890.7 GDD and 139 days.Both plants passes the early stages of growth and ‎germination concurrently, Maize, however, ‎comleted Vegetative growth and seed ‎ripening more earlier than annual ground cherry. ‎Also, the results of studying the effect of different densities of ‎annual ground cherry on yield and yield components of corn including 1000-seed weight, number of seeds per ear row, corn harvest index and leaf area index showed that all these traits decreased by increasing density of annual ground cherry. However, the number of seed rows per ear, which is genetically-control trait, was not affected by competition with annual ground cherry. In contrary to the above traits, the density of this weed increased with the effect of increasing the height of corn and as a result, increasing the biomass of corn compared to control. In general, weed densities of the 8 and 16 plants m-2 decreased maize yield by 10 and 14 percentages, respectively.

The results of this study suggest that if corn fields are infected with this weed and we do not ‎succeed in combating it in the early stages, earlier harvest of corn in the fall will allow it to be ‎harvested by cultivation methods or using a general herbicide of this weed before its seeds are fully ‎ripen.

To study the effect of application of plant growth promoting rhizobacteria (PGPR) including; Azotobacter chroococcum, Azospirillum lipoferum, Azospirillum brasilense and Pseudomonas fluorescens on phenology and grain yield of late maturity maize (Zea mays L.) hybrids (KSC700, KSC704 and a promising single cross, B73×K18), a field experiment was conducted in two successive cropping seasons. Exprimental treatments including seeds of maize hybrids inoculated with single (one by one bacteria) and co-inoculated by two and three bacterial combined inoculants and no inoculation as control. Duration from planting to seedling, fourth, eighth and tvelveth leaf, tassel,ing pollen and silk emergence, pollen shedding termination, silk desiccation and grain physiologic maturity as well as vegetative growth period, pollination, silking, coincidence of flowering and grain filling periods were detrmined using Growing Degree Days (GDDs). Grain yield per hectare was also determined. Results revealed that PGPRs affected phenology of maize hybrids as leaf, tassel, pollen and silk emergence was accelerated and duration of pollination, silking, coincidence of flowering and grain filling period was prolonged. Corrolation coefficients analysis revealed that GDD for developmental periods and phonological events were positively correlated. It was also revealed that application of inoculantion with combination of all bacteria inoculats had the highest promoting effect on phenology of maize hybrids,. Co-inoculation of seeds by Azotobacter chroococcum and Pseudomonas fluorescens and inoculation of seed by each of them had also high promoting effect, respectively. Maize hybrids had differed in their phonological response to application of PGPR and KSC704 responded more vigorously than other hybrids, followed by B73×K18 and KSC700, respectively. The highest grain yield obtained from KSC700 co-inoculated with all bacteria.