The cultivation of Mitragyna speciosa (kratom) has gained significant interest due to its diverse alkaloid profile, increasing its commercial and medicinal demand. Using controlled hydroponic techniques, this study investigates the effects of varying light intensity and water potential on kratom growth, mitragynine (MG) accumulation, and total alkaloid content (TAC). While the interaction between light and water potential was generally not significant, water potential emerged as the dominant factor affecting plant growth and alkaloid accumulation. The highest MG accumulation (0.63% w/w) was recorded under moderate water potential (−0.4 MPa). In contrast, the highest TAC (8.37 mg alkaloid equivalent per gram dry weight) was observed under the combined effect of low light and mild water potential (−0.4 MPa). Leaf age also played a key role, with younger leaves (second and third pairs) accumulating significantly higher MG levels (0.74% w/w) than older leaves (0.40% w/w). Additionally, leaf thickness was positively associated with MG levels, suggesting a potential link between plant morphology and alkaloid biosynthesis. However, low water potential (−0.7 MPa) significantly reduced both growth and MG content, highlighting the importance of optimizing environmental conditions for sustained bioactive compound production. These findings demonstrate the physiological adaptability of kratom to variable environmental stresses and their influence on alkaloid accumulation. This knowledge can be applied to precision cultivation strategies to enhance the sustainability of kratom farming while optimizing the production of bioactive compounds for pharmaceutical and agricultural applications.

Kratom (Mitragyna speciosa (Korth.) Havil.) is a tropical evergreen species native to Southeast Asia, widely recognized for its medicinal properties. Recent legal changes in Thailand permitting its cultivation and commercial use have increased interest in understanding the optimal conditions for its growth, particularly in regions beyond its native southern habitat. This study examined the leaf functional traits associated with kratom’s growth in the southern (native habitat), central, and northeastern regions of Thailand. Species adaptation was determined by analyzing variations in leaf functional traits across different environments. The results showed that the specific leaf area (SLA), leaf thickness, chlorophyll content (SPAD), and stomatal density (SD) did not exhibit any significant regional variations. However, the leaf pH, performance index (PI), and quantum yield (Fv/Fm) differed significantly across regions. The northeastern region had higher leaf pH and lower photosynthetic efficiency compared to the southern and central regions. Non-Metric Multidimensional Scaling (NMDS) ordination indicated that environmental factors such as elevation, light intensity, temperature, and soil water content significantly influenced leaf trait variability in the northeastern region. These findings demonstrate kratom’s ability to grow under diverse environmental conditions, potentially indicative of cultivation beyond its native range.