JWSS - Journal of Water and Soil Science

Sensitivity of developmental stages of three sunflower cultivars to day length and temperature changes under field conditions were evaluated, and their development rates during various growth stages were modeled in a field experiment conducted in 1996 at the Agricultural Research Station, Isfahan University of Technology. Five dates of planting (April 27, May 12 and 27, and June 12 and 29) and three open pollinated sunflower cultivars (Record, Vnimik 8931 and Armavirec) were evaluated using a randomized complete block design with split-plot layout in three replications. Date of planting was considered to be the main plot and cultivars were randomized in sub-plots.

Number of days from planting (P) to head visible (HV) and P to first anther (FA) were significantly reduced with delay in planting as the result of increase in temperature during these periods. Number of days from P to physiological maturity (PM) was also significantly reduced with delay in P. This response, however, could not be explained by changes in temperature variables or day length. Number of days from HV to FA, in harmony with the partial stability of maximum and minimum temperatures during this period, was not affected by date of planting. Duration from FA to PM of the last planting date was significantly shorter than the other planting dates. This response was related to the persistence of the effect of high and stable maximum temperatures prevailing during HV to FA period of the last planting date. Armavirec was significantly earlier than Record and Vnimic 8931 for number of days from P to HV and from P to FA Cultivars showed significantly large differences for the FA to PM and P to PM durations. Armavirec was the earliest and Record was the latest cultivar. Based on the results obtained, it may be concluded that the cultivars under study were non-sensitive to photoperiod. Development rate (DR) of Armavirec responded linearly and DR of Record and Vnimic 8931 responded non-linearly to increases in temperature variables during P to HV and P to FA Development of Vnimic 8931 was faster than Record at high temperatures. DR of the cultivars decreased linearly during P to PM as day length increased. The relationship between DR and photoperiod could be used as a practical model for estimating P to PM duration of these sunflower cultivars.

  During the past years, safflower genotypes have been selected from local variety of Isfahan, named Kouseh. The response of these genotypes to planting date might be different. To determine this, performances of several genotypes selected from Kouseh plus Arak 2811 ) as check ( were studied at the Agricultural Research Station, Isfahan University of Technology in 2002-2004. The experiment was conducted using a split-plot arrangement within a randomized complete block design with three replications. Planting dates were considered as the main plots and subplots consisted of 22 genotypes of safflower. Number of days from planting to emergence was highest (18.0 days) in early spring planting and lowest (10.3 days) in late spring planting. Days from planting to head visible, flowering and physiological maturity were decreased with delay in planting from autumn to late spring. Days from planting to emergence, head visible and physiological maturity were not influenced by genotype. Genotypes C116 and DP29 had the highest (145.0) and genotype ISF28 the lowest (140.2) days from planting to flowering. Plant height, number of first and second degree branches, number of heads per first and second degree branches, number of seeds per head, 1000-seed weight and seed weight per plant reduced significantly with delay in planting from autumn to late spring. Genotypes C128 and DP7 had the highest (120.0 and 120.5 cm, respectively) and genotype DP9 the lowest (104.2 cm) plant height. Genotypes DP6 and DP9 had the highest (12.8) and the lowest (6.7) first degree branches per plant, respectively. Arak-2811 had the highest (16.9) and genotypes DP9 and DP5 the lowest (7.2 and 7.1, respectively) second degree branches per plant. Number of heads per first degree branches was not significantly affected by genotype. Arak-2811 and genotype C114 had the highest (12.8 and 12.2, respectively) and genotype DP9 the lowest (5.1) number of heads per second degree branches. Genotype DP7 had the highest (45.9) and genotype C111 had the lowest (28.0) number of seeds per head. Genotypes DP3 and C128 had the highest (34.2 g) and lowest (22.0 g) 1000-seed weight, respectively. Genotype DP25 had the highest (20.5 g) and genotypes DP29 and DP9 the lowest (9.9 and 10.0 g) seed weight per plant. Harvest index was not affected by planting date and genotype. The result of this study showed that safflower may yield more in fall planting under conditions similar to this experiment. Genotype DP25 might be recommended for this planting date, genotypes ISF66 and DP25 for early spring planting and genotypes DP7 and ISF14 for summer planting.