Blossfeldia liliputana and survival of severe dehydration

A plant with variable water content

Blossfeldia liliputana grows in sheltered rock crevices in Bolivia and Argentina. A flowering stem is often only about a centimetre in diameter. After losing water, it becomes markedly flatter and decreases in volume. Barthlott and Porembski described the plant as poikilohydric. The term denotes a strong dependence of tissue hydration on environmental water availability, combined here with the ability to survive severe drying. [Barthlott and Porembski 1996, pp. 161–165]

Succulence consists of storing water in extensive living tissues. In Blossfeldia, it is accompanied by the capacity for deep dehydration and subsequent rehydration. The study concerned entire small plants, their structure and changes in mass over time, allowing stem form to be related to tissue function. [Barthlott and Porembski 1996]

Where the figure of about 80% comes from

In the experiment lasting many months, the mass of drying plants fell to about 18% of its initial value. This corresponds to a loss of around 82% of the whole plant's initial mass. The steepest decrease occurred during the first year, and very low mass persisted through the rest of the experiment. Observation covered more than two years. [Barthlott and Porembski 1996, Fig. 4 and experimental results]

The reference was plant mass at the start of the experiment. Determining the proportion of water in tissue would additionally require dry mass, and determining relative water content would also require mass at full saturation. The published curve thus presents changes in whole-plant mass relative to a particular initial state. [Barthlott and Porembski 1996, methods and Fig. 4]

After water was supplied again, mass increased severalfold within two weeks, and stems regained volume and green colour. The authors observed rehydration and greening. They considered recovery of assimilation likely, but did not directly measure CO₂ uptake in this part of the experiment. [Barthlott and Porembski 1996, pp. 164–165]

Tissues adapted to changes in volume

Parenchyma fills most of the stem. The surface is covered by a thin epidermis with a delicate cuticle, lacking an extensive wax layer. There is no reinforcing collenchymatous hypodermis beneath the epidermis. Short, narrow xylem elements have spiral wall thickenings. The authors linked this structure to the ability of the body to shrink and expand considerably. [Barthlott and Porembski 1996, pp. 163–165]

Anatomy describes the spatial and mechanical aspects of dehydration tolerance. The 1996 publication did not identify protective proteins or gene regulation pathways responsible for survival. The physiological outcome of the experiment is well defined, while its molecular explanation requires other research methods. [Barthlott and Porembski 1996]

Few stomata and CAM

Mean stomatal density was around 0.6 per mm². Stomata were clustered deep in areole depressions, sheltered by hairs. This position changes the gas exchange pathway between the stem surface and surroundings. In the sample of five plants studied, the mean describes a surface with a highly uneven stomatal distribution. [Barthlott and Porembski 1996, pp. 163–164]

Carbon isotopic composition, δ¹³C around −15.92‰, indicated a contribution from CAM photosynthesis. This measurement records the integrated effect of earlier carbon fixation. Stomatal opening times, the magnitude of CO₂ uptake and changes during drought are quantities determined by measuring gas exchange and metabolites. [Barthlott and Porembski 1996, p. 164]

The areole as a site of water contact

In a dye experiment, the authors demonstrated water uptake through areole regions. A small plant can therefore regain water through the stem surface too. Its sheltered position in a crevice, thin covering layer and distinctive areole organisation combine to create its own way of functioning in a periodically dry environment. [Barthlott and Porembski 1996, pp. 164–165]

A description of the stem, root, flowers and dispersal by ants is found in the profile of Blossfeldia liliputana. Data on regeneration from seedling fragments develop a second aspect of the species' biology, its capacity to form new organs in controlled culture. [Barthlott and Porembski 1996][Ivannikov et al. 2022]