Quantifying dry matter production and partitioning in safflower (Carthamus tinctorious L.)

Abstract
Introduction
Simulation crop models are a robust tool to improve crop management and to study yield limiting and reducing factors. Crop parameters related to phenology, leaf area and dry matter production and partitioning are needed to simulate crop growth and yield. Therefore, the aim of present study is to quantify the dry matter production and to estimate dry matter partitioning coefficients to different crop parts (stem, leaf and grain).

Materials and Methods
A factorial experiment was conducted based on completely randomized block design with four replicates and three sowing dates (4 April, 25 April and 16 May) and four cultivars (411, Sina, Local Isfahan and Sofeh) in Research Farm of Rafsanjan Vali-e-Asr University in 2011. Sampling was done at an interval of 5-10 days from two weeks after planting and continued up to end of the growing season. On each sampling, the leaf, stem and grain dry matter weight were measured. The truncated expolinear model was fitted on total dry matter weight (w) data over the time (t). Coefficient of dry matter partitioning to different crop parts (leaf, stem and grain) was obtained by fitting the linear regression model on dry matter weight of each part versus total dry matter weight.


Results
Results showed that the model well described the trend of dry matter production versus days after planting. According to the model, the maximum dry matter accumulation in all three planting dates was obtained 972-1179, 576-611 and 191-277 gm-2, respectively. Coefficient of dry matter partitioning to leaves ranged from 0.45 to 0.51 in the first planting date, 0.51 to 0.60 in the second planting date and 0.44 to 0.61 in the third planting date. There was no different between the coefficients of cultivars. Coefficient of dry matter partitioning to stem in all three planting dates were 0.35-0.49, 0.24-0.44 and 0.14-0.23, respectively. There was no significant difference among the cultivars. Partitioning coefficient to grain was between 0.16 and 0.44 for the first planting date that was lower than the second planting date. In the third planting date, the coefficient was between 0.35 and 0.76 that there was a significant difference among the cultivars.

Conclusion
It was concluded that the trend of the dry matter production and partitioning is affected by environmental condition (temperature and solar radiation) and cultivar. The results showed that with delay in planting date crop growth rate and dry matter production were decreased. In such condition, coefficient of dry matter partitioning to stem was decreased and coefficient of dry matter partitioning to leaves and grain was increased.