Optimal methods for estimating cactus pear biomass using cladode dimensions of morphologically diverse accessions

Authors: ANGRES, GABRIEL - University Of Reno; Heinitz, Claire; CUSHMAN, JOHN - University Of Reno

Submitted to: Plant Cell and Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/26/2026
Publication Date: 5/5/2026
Citation: Angres, G.J., Heinitz, C.C., Cushman, J.C. 2026. Optimal methods for estimating cactus pear biomass using cladode dimensions of morphologically diverse accessions. Plant Cell and Environment. 2026: 1-21. https://10.1111/pce.70587.
DOI: https://doi.org/10.1111/pce.70587

Interpretive Summary: CAM plants, such as certain cacti and succulents, are highly efficient at using water and can tolerate heat much better than most other plants. This makes them an appealing option for sustainable crops that provide food, animal feed, fiber, and even biofuels. To grow these plants successfully on a large scale, farmers and researchers need reliable ways to measure crop yields. Traditionally, estimating plant growth involves weighing the biomass, which is costly, time-consuming, and requires a lot of labor. Newer methods use indirect measurements—like plant dimensions, images, or counts—to predict weight more quickly and at a lower cost. For plants with photosynthetic stems (called cladodes), such as cactus pear (Opuntia species), existing methods need improvement to work well in diverse field conditions. In our study, we measured the size and shape of cladodes from 14 different cactus pear varieties, including four species and two hybrids. We found clear differences in their shapes and developed models to estimate fresh weight without cutting the plants. The most accurate model used a “Box” approach, combining measurements like length, width, thickness, and diameter, achieving a very strong fit. Another method used images to calculate surface area, and a third used an elliptical shape approximation, which reduced the need for manual measurements. These models performed as well or better than previous methods and work across different cactus varieties. They provide efficient, non-destructive tools for estimating cactus pear biomass, making it easier to manage these crops sustainably.

Technical Abstract: Crassulacean acid metabolism (CAM) plants, which exhibit much greater water-use efficiency and heat tolerance than C3 and C4 photosynthesis plants, are increasingly attractive as sustainable food, feed, fiber, bioproduct, and biofuel crops. Further agricultural development of CAM plants requires reliable crop-specific yield measurement techniques. Traditionally, biomass production estimates are based upon gravimetric assessment, which is expensive, labor-intensive, and time-consuming. In contrast, indirect approaches that make accurate predictions from dimensional measurements, images, or object counts are simpler, faster, and less expensive. Current allometric methods for photosynthetic-stem (cladode) plants, such as cactus pear (Opuntia spp.) require refinement to be used in field settings in which diverse accessions are grown. We analyzed cladode dimensional data using 14 accessions representing four species and two hybrids to quantify statistically significant morphological differences among accessions and derived cross-accession models to approximate cladode fresh weight. A Box model using cladode dimensions (e.g., length, width, thickness, and diameter) and factorial combinations of these measures (e.g., length*width*thickness*diameter vs. fresh weight) resulted in the highest coefficient of determination (R2 = 0.95 general fit) across all accessions for estimating fresh weight along with parsimony estimates using the Schwarz-Bayes Criterion (SBC), which assesses the most consistent performance on individual accessions. A Fitting-box modeling approach used the measured cladode area captured using ImageJ (R2 = 0.93 general fit). Lastly, an Elliptical model used an elliptical approximation for the measured area and performed well over all accessions (R2 = 0.94 general fit) while avoiding extensive manual measurements. These models meet or exceed the performance of previously published approaches when applied across morphologically diverse accessions, providing efficient tools for non-destructive estimation of cactus pear biomass under the conditions tested.