In order to study two GRAINs FILLING characteristics (specific effective GRAIN FILLING PERIOD and effective GRAIN FILLING rate) to improvement of GRAIN yield this study was conducted during 1999 and 2000 growing season in Koohdasht dry land Research Station in Lorestan Province. An experiment using complete randomized block design which ten rain-fed wheat (Triticum aestivum L.) genotyps treatments with four replications was used. Also, to determine correlation coefficients between triats, parameters were measured consist of GRAIN yield, 1000 Kernel weight, harvest index, biological yield, straw yield, effective GRAIN FILLING rate, test weight. Results showed that a significant positive correlation between GRAIN yield with 1000 Kernel weight, Harvest index, biological yield, straw yield, effective GRAIN FILLING rate test weight and with number of days, to steming was a negative significant correlation. Results of the growth GRAIN process indicated that overall, at the end the linear of (Tr 8010200, Zagross) No. 4 and No.10 genotypes were the most final GRAIN weight (40mg) and genotypes (Pik/opatacm, Maya 74 "s") No. 2 and No. 7 were the least final weight GRAIN with 32 mg. Effective GRAIN FILLING PERIOD were among genotypes 18.39 to 25.03 days. The most effective GRAIN-FILLING PERIOD was 25 days related to No.10 (Zagross) genotype and the least No. 7 (Maya 74 "s") genotype with 19 days. Effective GRAIN FILLING rate among genotypes were 1.43 to 1.74 mg.days-1. The most and the least effective GRAIN-FILLING rate was for No. 2 (pik/opata) and NoA (Tr8010200) respectively. Between effective GRAIN FILLING rate and PERIOD were significant negative correlation (r=-46 %**).

Dry matter remobilization, GRAIN FILLING rate and duration has principle role on rice GRAIN yield, and environment condition directly affect on them. For study the influence of climate factors a factorial field experiment in randomized complete blocks design with three replications conducted at Haraz Extention and Technology Development Centre in Spring 2013. Treatments included rice cultivars namely; Samadi, Tarom Hashemi, Local Tarom, Shiroudi, Keshvari, Gohar and transplanting times (5th may, 20th may and 10th June). Results showed that dry matter remobilization rate, stem dry matter remobilization efficiency, GRAIN FILLING rate and duration, and GRAIN yield varied significantly among different transplanting times. Transplanting time on 5th may was higher than other two transplanting dates in all traits except for GRAIN FILLING rate. Tarom Hashemi had highest and improved variety, Shiroodi had lowest GRAIN FILLING rate. Dry matter remobilization rate, Stem dry matter remobilization efficiency, effective GRAIN FILLING duration, and GRAIN yield was higher in Shiroudi among rice cultivars. GRAIN yield negatively correlated with GRAIN FILLING rate. Increasing in GRAIN FILLING duration with increased dry matter remobilization had more effective role in rice cultivars GRAIN yield. Increasing temperature in vegetative growth phase with increasing in accumulated growing degree day accompanied with decreasing in tiller number, less tiller number caused higher GRAIN FILLING rate and lower GRAIN FILLING duration and dry matter remobilization restriction that decreased GRAIN yield.

In order to study the effect of heat stress during GRAIN FILLING PERIOD on yield, yield components, GRAIN FILLING rate and duration, a field experiment was carried out during 2010-2011 growing season in Ahvaz conditions, as factorial based on randomized block with three replicates. The experimental factors consisted of 10 mid maturity bread wheat genotypes (Charnran, Atrak, Aflak, Dez, Falat, Darab2, Kavir, Pishtaz, S-78-11, S-83-3) and two sowing dates, including the optimum (12 Nov.) and late sowing date (21 Dec.). The results showed that in late sowing date, yield and yield components were reduced significantly in all genotypes. Atrak and Pishtaz had the minimum (8.2 %) and maximum (26.3%) reduction of GRAIN yield, respectively. In late sowing date, Kavir and Charnran had the highest (584.3 and 579.8 g.m-2, respectively) and Pishtaz had the lowest (446.3 g.m-2) GRAIN yield. Based on the heat susceptibility index among all genotypes, Atrak was heat- tolerant, Charnran, Kavir, Dez, Falat and Aflak were moderately tolerant and S-78- 11, S-83-3, Darab2 and Pishtaz were heat- susceptible. The shortening of effective GRAIN FILLING PERIOD in late sowing date resulted in reduction of thousand-GRAIN weight and increase in GRAIN FILLING rate could not compensate for .GRAIN FILLING PERIOD reduction. Overall, it seems that only the higher GRAIN growth rate under heat stress during GRAIN FILLING PERIOD cannot contribute to the higher GRAIN yield and other factors such as GRAIN FILLING PERIOD and number of GRAINs per spike seem to be more important.

The linearity of harvest index (HI) increase has provided a simple means to analyse and predict seed growth and yield in experimental and simulation studies. The objective of this study was to Investigate harvest index linear increase and related parameters in FILLING GRAIN PERIOD of chickpea (Cicer arietinum) crops grown under well-watered conditions. A field experiment, with 3 sowing dates and 4 plant densities, was conducted in Gorgan during 2004-2005. Crop biomass and phenological stages were measured between emergence and maturity. Harvest index increased in seed FILLING PERIOD linearly. The effect of density on harvest index linear increase was not significant but there was different between sowing date. The time of beginning harvest index linear increase, decreased from 26 to 8 days from first sowing date to third one, but there was any difference in plant density. From obtained parameters in this research can use in chickpea growth simulation models.

The yield of maize in Iran is very low as compared to other maize producing countries. One of the most important effective factors is non application of optimal plant population per hectare and maize hybrids differ in their response to plant density. In order to study the effect of different plant densities on yield, rate and effective GRAIN FILLING PERIOD in maize hybrids, a factorial experiment based on randomized complete block design with three replications was conducted in 2007 at the Research Farm of the Faculty of Agriculture Mohaghegh Ardabili University. Experimental treatments were: maize hybrids in three levels (SC-404, DC-370, SC-504) with different plant densities (8, 10 and 12 plants.m-2). The results showed that yield and yield attributes characters (except of the number of GRAINs rows) varied significantly due to the variation in population densities. The number of kernel per ear and number of GRAINs per ear row increased with increasing plant density. The highest GRAIN yield was obtained from 10 plant.m-2 density. Response of maize hybrids wasn’t the same for plant densities. The highest GRAIN yield belonged to SC-504 hybrid and the least was in DC-370 hybrid. A two part linear model were used to quantifying the GRAIN FILLING parameters. Cultivars and plant densities affected all GRAIN FILLING parameters significantly.Maximum kernel weight, rate and effective GRAIN FILLING PERIOD was obtained in low plant densities.Means of comparisons showed that maximum of kernel weight (0.35 mg) and effective GRAIN FILLING PERIOD were obtained in SC-504 hybrid×8 plants.m2 and SC-404 hybrid×8 plants/m2. Minimum of it was obtained in DC-370 hybrid×12 plants/m2.

For studying genetic variation for GRAIN FILLING rate and GRAIN FILLING PERIOD  and relationship with GRAIN yield, 10 barley genotype: Bomi, Torkaman, Eize, Siah, Sahra,1-yeknavakht, 14G, 11G, 5G and 15G, cultivars ,introduced by Golestsn agriculture research centre, Were studied in randomized complete block design at 4 replication at 84-85.were studied. This genotype varied for both rate and duration GRAIN FILLING parameter and had significant difference. Torkaman had maximum GRAIN FILLING rate and minimum was for 1-yeknavakht.the average of GRAIN FILLING rate was 1.59 mg/day and average of GRAIN FILLING duration was 29.8 days. Positive correlation between GRAIN FILLING rate and duration with GRAIN yield showed that, they increased from low yield genotype to high yield.14G had maximum and Torkaman had minimum GRAIN FILLING duration. Negative no significant correlation between GRAIN FILLING rate and GRAIN FILLING duration.14G showed that have higher GRAIN yield than other genotype and with receive lower GDD, achieved to the physiological maturity

Relationship between GRAIN FILLING rate, GRAIN FILLING duration, yield components and other physiological traits of rice was investigated in 93 genotypes of rice at Rice Research Institute of Iran (Rasht, Iran) during the growing season of 2001-2002. The experiment was performed without any statistical design. Panicles of main stem were tagged and taken at 3- day intervals during the GRAIN FILLING PERIOD. A cubic polynomial model was used to fit the GRAIN dry weight data (mean of R2= 0.98 for all genotypes) and the GRAIN FILLING rate and duration estimated for the genotypes. Traits related to sink capacity such as GRAIN weight, GRAIN size and GRAIN number per panicle correlated with GRAIN FILLING rate but source capacity- related traits except chlorophyll content of flag leaf and secondary leaf did not correlate with GRAIN FILLING rate. Stepwise regression showed that final GRAIN weight, GRAIN FILLING duration and flag leaf angle contributed to GRAIN FILLING rate, however, path analysis showed that only final GRAIN weight and GRAIN FILLING duration had the greatest effect on GRAIN FILLING rate. The results of stepwise regression irrespective of final GRAIN weight showed that chlorophyll content of flag leaf, GRAIN width, GRAIN FILLING duration and GRAIN length contributed to GRAIN FILLING rate. Path analysis results showed that the final GRAIN weight had the greatest direct positive effect on GRAIN FILLING rate, while GRAIN FILLING duration had negative effect on GRAIN FILLING rate.

To optimize the GRAIN FILLING PERIOD of commercial wheat cultivars, an experiment was conducted at two agricultural research stations in the warm and humid agro-climatic zone of northern Iran. The experiment was conducted as a split plot with four replications. The main plots consisted of five sowing dates: 1 November (SD1), 16 November (SD2), 1 December (SD3), 16 December (SD4), and 31 December (SD5), and four spring wheat cultivars, namely Ehsan, Tirgan, Meraj, and Kalateh, were the subplots. The results indicated that the highest yield was obtained from SD3 (5892.2 kg ha-1). Despite the one-month difference between SD1 and SD3, the GRAIN FILLING PERIOD remained unaffected, providing suitable conditions for plant height and resistance to lodging across the different cultivars. At SD3, optimal conditions were established for the wheat cultivars regarding temperature, day length (DL), relative humidity (RH), and energy use efficiency during the GRAIN FILLING PERIOD. Both SD2 and SD3 exhibited the highest energy use efficiency. The GRAIN yield at SD1 decreased due to severe plant lodging, while exposure to terminal heat and drought stresses, and shortened GRAIN FILLING PERIOD reduced yield at SD4 and SD5. For the early anthesis cultivar, i.e., Kalateh, the GRAIN yield was significantly higher than that of the other cultivars. The GRAIN FILLING PERIOD for the early anthesis cultivar was not significantly different from the others, allowing the plant to escape terminal heat and drought stresses, thereby increasing energy use efficiency and, consequently the GRAIN yield. Therefore, the early anthesis cultivar is highly suitable and recommended for cultivation in the studied zones where terminal heat and drought stresses are prevalent at optimal sowing dates.

To optimize the GRAIN FILLING PERIOD of commercial wheat cultivars, an experiment was conducted at two agricultural research stations in the warm and humid agro-climatic zone of northern Iran. The experiment was conducted as a split plot with four replications. The main plots consisted of five sowing dates: 1 November (SD1), 16 November (SD2), 1 December (SD3), 16 December (SD4), and 31 December (SD5), and four spring wheat cultivars, namely Ehsan, Tirgan, Meraj, and Kalateh, were the subplots. The results indicated that the highest yield was obtained from SD3 (5892.2 kg ha-1). Despite the one-month difference between SD1 and SD3, the GRAIN FILLING PERIOD remained unaffected, providing suitable conditions for plant height and resistance to lodging across the different cultivars. At SD3, optimal conditions were established for the wheat cultivars regarding temperature, day length (DL), relative humidity (RH), and energy use efficiency during the GRAIN FILLING PERIOD. Both SD2 and SD3 exhibited the highest energy use efficiency. The GRAIN yield at SD1 decreased due to severe plant lodging, while exposure to terminal heat and drought stresses, and shortened GRAIN FILLING PERIOD reduced yield at SD4 and SD5. For the early anthesis cultivar, i.e., Kalateh, the GRAIN yield was significantly higher than that of the other cultivars. The GRAIN FILLING PERIOD for the early anthesis cultivar was not significantly different from the others, allowing the plant to escape terminal heat and drought stresses, thereby increasing energy use efficiency and, consequently the GRAIN yield. Therefore, the early anthesis cultivar is highly suitable and recommended for cultivation in the studied zones where terminal heat and drought stresses are prevalent at optimal sowing dates.