Best Collection Time For observing active mitotic divisions in rice (Oryza sativa), collect root tips in the morning (8:00–10:00 AM) when mitotic activity peaks due to circadian rhythms15. While direct rice-specific timing data is limited, studies on onion and lentils confirm higher mitotic indices during morning hours, which likely applies to rice

Optimal Root Age Use 2–3-day-old roots post-germination, as younger roots exhibit rapid cell division in the apical meristem Onion studies suggest slightly older roots (5–7 days) may work, but rice roots grow faster, making earlier stages ideal

Key Factors

• Apical region: Focus on the 1–2 mm root tip containing the root apical meristem (RAM), where mitotic activity is highest
• Mitotic stages: Prophase is most common, but metaphase (critical for chromosome analysis) is best observed in morning samples

Supporting Evidence

• Circadian influence: Onion studies confirm morning mitotic peaks, aligning with conserved plant cell cycle regulation
• Root growth: Rapid cell division in young rice roots ensures high mitotic indices, similar to onion root behavior

Raghad Mouhamad Thank you