Euphorbia tirucalli

Name and range

Euphorbia tirucalli L. is accepted in POWO, checked on 21 October 2026. The species belongs to Euphorbiaceae in the order Malpighiales. Its synonyms include Arthrothamnus tirucalli, Tirucalia tirucalli and Euphorbia media [2-WWW].

The current POWO record identifies Madagascar as the native range. Many areas of continental Africa, Asia and other parts of the world are listed as introduced range. This is narrower than the origin described in introductions to older physiological studies. The status of a locality should therefore be distinguished from the country where experimental material was obtained [2-WWW] [Hastilestari et al. 2013] [Abuelsoud and Papenbrock 2019].

Stems, leaves and reproductive structures

The plant forms a densely branched, spineless shrub or tree. The regional flora description gives branchlet thickness as 5–7 mm and the length of the narrow, soon-shed leaves as 8–15 mm. Small cyathia occur in clusters at branch tips. A cyathium is the characteristic spurge structure containing reduced flowers. The described fruit capsules are about 8 mm in diameter and rounded with three angles [18-WWW].

Leaf and stem photosynthesis

Succulent stems carry out CAM photosynthesis, involving daily accumulation and use of organic acids. The nonsucculent leaves are described as C₃ organs. In an experiment on two genotypes, Morocco and Senegal, stems showed differences in malate content between the end of the night and the end of the day. After eight weeks of water limitation at 10% VWC, a similar difference was detected in leaves of both genotypes [Hastilestari et al. 2013].

The leaf result supports possible CAM induction, but the study did not directly measure nocturnal CO₂ uptake by leaves. Day–night malate variation alone does not establish the source of the carbon being fixed. The authors identified a need for further enzyme and gas-exchange analyses. Carbon metabolism and the different measurement approaches are explored in the article on drought responses in E. tirucalli [Hastilestari et al. 2013].

Growth and roots under water limitation

In the 2013 study, six-month-old plants of both genotypes grew for eight weeks at 25%, 15%, 10% or 5% volumetric water content in the substrate. Moisture was maintained through monitoring and replenishment. Water limitation reduced shoot growth, increased taproot length and raised the root-to-shoot mass ratio. Changes therefore involved both total growth and biomass allocation [Hastilestari et al. 2013].

At the lowest VWC, Morocco reached a greater height, but Senegal still had a higher shoot dry mass. Fv/Fm, an indicator of maximum photosystem II efficiency derived from chlorophyll fluorescence, declined in leaves and stems. All plants survived the experimental period. This comparison separates survival, growth and photosynthetic function, which describe different aspects of drought tolerance [Hastilestari et al. 2013].

Antioxidant defence

A separate experiment in 2019 compared 25% and 10% VWC over eight weeks. Ascorbate peroxidase and peroxidase activities increased in Morocco stems, while catalase activity increased in Senegal stems. These enzymes contribute to H₂O₂ removal. The amount of reduced glutathione also increased in stems of both genotypes. Leaves responded differently, including decreases in several of the measured enzyme activities [Abuelsoud and Papenbrock 2019].

Measurements of H₂O₂, MDA and extract antioxidant capacity require their units to be retained. In dehydrated tissue, a result expressed per dry mass can change differently from one expressed relative to tissue water. The authors’ proposed involvement of H₂O₂ in leaf death and shedding was not tested directly. Increased enzyme activity describes a biochemical response and does not alone establish the cause of greater tolerance [Abuelsoud and Papenbrock 2019].

Vegetative propagation and cultivation evidence

In the 2013 study, material was propagated from stem pieces 10–15 cm long and maintained for six months before the experiments. The described growth phase used a clay-loam and sand mixture, at 24°C during the day and 22°C at night, with fourteen hours of light. This documents the use of cuttings to produce experimental material. The publication does not establish a rooting percentage or an optimal propagation date for domestic cultivation in Poland [Hastilestari et al. 2013].

Experimental VWC values and observation periods describe particular containers and environmental conditions. They do not determine watering frequency for a plant in another substrate or light regime. Continued growth under restricted water occurred alongside declining photosystem efficiency. The studies investigate physiological responses rather than optimizing care in a home [Hastilestari et al. 2013] [Abuelsoud and Papenbrock 2019].

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