PENGARUH LAMA PENCAHAYAAN TERHADAP PERTUMBUHAN TANAMAN KASTUBA MERAH SEBAGAI SUMBER BELAJAR BIOLOGI

This research aimed to analyze the effect of light duration on the growth of Red Poinsettia (Euphorbia pulcherrima) and its use as a biology learning resource. Plant growth was influenced by both internal and external factors such as genetics, nutrients, water, temperature, and light intensity. Among these factors, light played a crucial role in photosynthesis, which affected plant height, stem diameter, leaf width, and overall biomass. Previous studies indicated that 10 hours of light exposure could significantly enhance the growth and coloration of Red Poinsettia, but variations in light duration might produce different physiological responses. This study used a true experimental method with a Pretest–Posttest Control Group Design. The independent variable was light duration (1–10 hours), while the dependent variables were plant height, stem diameter, leaf width, and plant weight. Data were analyzed using ANOVA, Mann–Whitney, and Independent t-test. The results showed that light duration had a significant effect on most growth parameters (p < 0.05). Ten hours of light exposure produced the most optimal growth, especially in plant height and stem diameter, whereas natural sunlight increased biomass due to its complete light spectrum. It was concluded that regulating light duration was an essential factor in improving Red Poinsettia growth quality and that the findings could serve as contextual learning material in biology education.