In: Phyton 56, Fasc. 1 (2016): S. 27-38 DOI: 10.12905/0380.phyton56(1)2016-0027

The Morphometry of Quadrifid Digestive Glands in Traps of Three Utricularia Species: Does Gland Size Correlate with Trap Size?

By

Lubomír Adamec, with 1 Figure

Key words: Aquatic carnivorous plants, Utricularia vulgaris, Utricularia australis, Utricularia stygia, digestive-absorptive glands, gland arm morphometry, trap size, species determination.

Summary
Adamec L. 2016. The morphometry of quadrifid digestive glands in traps of three Utricularia species: does gland size correlate with trap size? – Phyton (Horn, Austria) 56 (1): 27–38, with 1 figure.

Quadrifid glands inside Utricularia traps consist of a basal cell and a tetrade of X-shaped terminal cells known as the long and short arms. They have digestive and absorptive functions associated with plant carnivory but their morphometry is commonly used for species determination. The interrelationship between the mor­phometric parameters of quadrifid glands in mature traps and trap length was esti­mated in three aquatic Utricularia species (U. vulgaris, U. australis, U. stygia). In these species, the ratio of trap length between the largest and smallest traps meas­ured was 2.3–2.7. The total variability of width of both the long and short arms was relatively low in all species but the length of both the long and short arms was much greater; the ratio between the maximum and minimum lengths in each species was within 1.9–2.6. Linear regression models revealed significant correlations between long arm lengths and trap lengths in all species. This also applied for short arms except in U. australis. In U. vulgaris and U. australis, both the long and short arm widths correlated highly significantly with trap length, while the correlation was significant only in U. stygia short arms. In all species, the angles between the long arms did not correlate with trap length. With the short arms, the angles correlated highly significantly with trap length only in U. stygia, but not at all in the other spe­cies. For species determination purposes, only mature traps of uniform, mean size should be used to reduce the otherwise great variability of gland morphometry.