Identifying features and variation
Tubercles are triangular in outline with a strongly sculptured surface. A groove with a woolly areolar zone runs along their centre. Appearance varies among populations. Plants formerly called lloydii may be more convex, with thicker, rounded tubercles. [Romulski 2006b]
POWO includes A. lloydii and several variety names among the synonyms of A. fissuratus. The older name hintonii instead leads to A. bravoanus subsp. hintonii. Keeping a label name may document the plant's history even when it does not match the current taxonomic treatment. [2-WWW]
Range and habitat conditions
The range includes southwestern and southern Texas and part of Mexico. The flat growth form makes plants inconspicuous among stones. Root and temperature studies used material of the species associated with rocky substrates in the Chihuahuan Desert. [2-WWW] [Garrett et al. 2010]
Plants from different parts of the range need not have identical features or respond equally to every cultivation treatment. The Polish account of the species described stem and habitat variation, with particular attention to careful repotting of plants with sensitive roots. [Romulski 2006b]
Contractile root
The root draws the stem down through changes in internal structure. Radial parenchyma cells expand, and xylem elements can shorten along the root axis. Broad bands of thickening in tracheid walls allow part of the conducting system to deform without retaining the rigidity typical of a strongly woody root. [Garrett et al. 2010]
Root contraction was observed in different seasons and moisture treatments. The movement was not solely caused by contraction of a dehydrated stem. The mechanism was demonstrated directly in A. fissuratus, so extending its details to every species of the genus requires separate confirmation. [Garrett et al. 2010]
Overheating and the role of stones
During a heatwave in an experiment in Los Angeles, stems at the surface of stony substrate heated less than those at the surface of sand. After further observation, five plants in the stony treatment survived, while five in sand died. This small, precisely defined experiment shows the importance of the stem's surroundings. [Garrett et al. 2010]
In heat resistance studies, results also depended on the temperatures to which the plant had previously acclimated. Assessments included cell condition after heating. A temperature causing injury to some tissues in such a test is not a safe temperature for a pot in a greenhouse. [Nobel et al. 1986] [Garrett et al. 2010]
Flowers, insects and self-pollination
Flowers are pink to magenta. In field studies over two seasons, October flowering had a short, distinct peak. Flowers opened during the day, usually for one or two days, and flower number was associated with plant size. [Martínez-Peralta and Mandujano 2011]
Bees, wasps and other insects were observed visiting, but their behaviour differed. Bees contacted the stigma and anthers in ways favouring pollen transfer. Flowers isolated from insects produced no fruits through spontaneous self-pollination. [Martínez-Peralta and Mandujano 2011]
Darkling beetles ate flower parts. Severe damage to reproductive organs can limit fruit formation. A bitten petal alone does not describe the scale of damage, so the study distinguished partial from complete flower destruction. [Martínez-Peralta and Mandujano 2011]
Surface and stem anatomy
A thick cuticle and prominent projections of epidermal cells were described microscopically. Stem cortex also contained clusters of terminal tracheids associated with the peripheral conducting network. Their presence is an anatomical feature whose particular ecological function remains unresolved. [Loza-Cornejo and Terrazas 2003] [Mauseth 2018]
Cultivation and seed production
When repotting, limit damage to the thick root and fit the pot to its structure. The Polish account recommends a permeable substrate and watering according to drying. Thermal experiment results also support monitoring temperature beside the stem itself, alongside greenhouse air temperature. [Romulski 2006b] [Anonim 2006] [Garrett et al. 2010]
Neciu recorded the first flowering of his seedlings at five years old. For seeds from controlled pollination, the provenance of both parents and matching flowering times matter. Field results indicate that several flowers on one plant do not guarantee good fruit set from self-pollen. [Neciu 2006] [Martínez-Peralta and Mandujano 2011]
Stem position and thermal surroundings
Root contraction was measured using markers at the stem base. Separate ink marks estimated shortening of the stem itself, which accounted for less than 10% of its lowering. In the older root portion, parenchyma between xylem bands expanded radially, and the distance between annular tracheid thickenings decreased. This set of measurements links whole-plant movement to root tissue deformation. [Garrett et al. 2010, p. 1952–1956, ryc. 1–2]
During an eight-day heat episode, five plants growing at the sand surface were compared with five at the surface of substrate covered by stones. Maximum temperatures inside the stems were 60.0 and 56.5°C respectively. After two months of further observation, all plants in sand had died and all among stones had survived. The relationship to the type of surroundings and the measurement method are explained in the account of the contractile root and thermal conditions. [Garrett et al. 2010, p. 1953–1957, ryc. 4–6]
Flower lifespan changes between seasons
In Cuatrociénegas, 26 flowers were observed in 2005 and 27 in 2006. One-day flowers predominated in the first season and two-day flowers in the second. The flowering peak of the whole observed population lasted about five and three days respectively. The short availability of each flower and concentrated flowering by many plants together create conditions for insect pollen transfer. [Martínez-Peralta and Mandujano 2011, p. 148–150]