This research had aimed to determine variations in form of calcium oxalate (CaOx) crystals in porang. Slides for microscopic observation were prepared from sliced leaf, petiole, and tuber of porang. Sliced organs were cleared by using modified clearing method. The parameters that were observed included form and variety of morphology type of CaOx crystals. Microscopic observation showed there were four basic forms of crystals, i.e., druse, raphide, prism and styloid with some variation of diverse types, each of which had 49, 10, 8, and 5 variations. CaOx crystals, based on the size, were grouped into large (20 -250 µm) and small (1 -15 µm) crystals.

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Harvest time is assumed to potentially influence shape and size variation of calcium oxalate (CaOx) crystals; therefore it needs to be observed microscopically. This research used porang corms from the second growing period which were planted to produce the vegetative phase of third growing period. These corms were obtained based on the harvest time had determined. The harvest time was determined, i.e. 1) at two weeks before the plants shed (R0 − 1); 2) when the plants shed (R0) and 3) at two weeks after the plants shed (R0 + 1). Slides for microscopic observation were obtained from slices on the edge and center of porang corms. Organ slices were cleared using modified clearing method. Parameters observed were the shape and the size of CaOx crystal. The variations of styloid, prism, druse and raphide crystals found in porang corms at the three harvest time were 1, 2, 3 and 37 variations respectively. The variation of CaOx crystals tended to be same in porang corms at three harvest times. The variation of these crystals tended to be static. It is also known that raphide crystal has the greatest variation amount. On the contrary, styloid crystal has the fewest variation amounts. This abundance of a number of raphide crystal variations is possibly due to its role as a defense mechanism in porang corms.