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'Thorny' cacti sprout ultra tiny leaves, reveals new study

From our ANI Correspondent

Washington, Aug 19: Cactus conjures up images of a thorny leafless plant standing tall in a hot barren desert. But, now a new study by an American biologist from the University of Austin at Texas has shown that cactus do actually possess ultra tiny leaves.


"For curious cacti owners desiring a glimpse of the leaves, caution is advised. If people do look closely at their cacti trying to see leaves, they need to be careful of spines close to their eyes," said James Mauseth, professor of biological sciences at the university, and lead author of the paper.

Prof. Mauseth said the leaves, which are best viewed under a microscope, exist at the base of spine clusters.

He said he made the determination after gathering samples of 147 different cacti species, most of which he obtained in the wild.

Then he conducted extensive analysis of the plants and their tissues under high magnification, he told Discovery News.

He said while the leaves "had more or less normal morphology," almost all were missing blades.

Just over half had xylem, a tissue that conducts water and nutrients from the roots up through the plant, but no cacti leaf analyzed had just phloem, which is a food-conducting tissue, he said.

Leaf sizes ranged from 30 to 2310 micrometers. A single micrometer is equal to one millionth of a meter or just .00003937 inch, so the documented cactus leaves may very well be the world's smallest, he added.

He further said cacti began as regular, leafy plants in the Americas, with many species later evolving spines.

"Some cacti, in fact, still have large leaves and stems, such as the pad-like stems on prickly pears, or the big, flat thin leaves found on certain genus Pereskia cacti that look like trees. Most leaves absorb the sun's rays, manufacture plant sugars, and help with water absorption and respiration. In the case of microscopic cacti leaves, however, something else is at work," Prof. Mauseth wrote in his study in the International Journal of Plant Sciences.

He said cacti would need even the tiniest of leaves in order for the plant to establish its axillary buds, which emerge near where leaves attach to the main stem.

"So the plants cannot lose leaves altogether, or they might then not be able to produce buds, or would produce them in the wrong spot," he said, adding that cacti genetically controlled their leaf size, in part, through release of plant growth hormones, such as auxin.


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