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Evaluation of Physiological Growth Indices of Two Commercial Sugarcane Cultivars under Different Plant Densities Using Sigmoid Models
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Habibolah Roshanfekr *   , Alireza Azizi , Payman Hassibi , Hossien Noroozi |
| Department of Plant Production and Genetics, Faculty of Agriculture, Shahid Chamran University of Ahvaz, Ahvaz, Iran. |
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Abstract: (33 Views) |
Stem density is one of the most important management factors in sugarcane cultivation, directly affecting the physiological growth indices. This study was carried out with the aim of evaluating the effect of four stem density levels (22, 24, 26, and 28 stems per square meter) on seven physiological growth indices, including leaf area index, crop growth rate, net assimilation rate, leaf area duration, leaf area ratio, leaf weight ratio, and specific leaf area, in two commercial cultivars, CP69‑1062 and CP48‑103. The experiment was conducted as split plots in a randomized complete block design with three replications at the Amir Kabir Sugarcane Agro‑Industry Farm in Ahvaz (southern Khuzestan Province).The results showed that the density of 22 stems provided the best conditions for crop growth rate, net assimilation rate, leaf area ratio, and specific leaf area, while the density of 28 stems resulted in the highest values of leaf area index, leaf weight ratio, and leaf area duration. Comparison of the cultivars indicated that CP69‑1062 had greater stability, whereas CP48‑103 showed greater sensitivity to increasing density. At densities above 26 stems, a severe decrease in physiological indices (except for leaf area index, leaf weight ratio, and leaf area duration) was observed. Growth modeling using three sigmoidal models (logistic, Gompertz, and Richards) showed that the logistic model had the best overall fit for evaluating the seven indices, whereas Richards model, due to having a flexible shape parameter (d), provided higher accuracy for net assimilation rate, leaf area ratio, leaf weight ratio, and leaf area duration, which have asymmetric patterns. The parameters of the models (x₀, a, b, d) quantified the patterns of variation in physiological indices under different stem densities. Based on logistic and Richards models, a density of 22–24 stems for CP69‑1062 and 22–26 stems for CP48‑103 is recommended.
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| Keywords: Logistic model, Richards, intraspecific competition and nonlinear regression. |
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Full-Text [PDF 1717 kb]
(11 Downloads)
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Type of Study: Research |
Subject:
Crop Physiology
Received: 2025/12/25 | Accepted: 2026/08/1 | Published: 2026/08/1
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