FIGURE LEGENDS
Figure 1. (A) Biomes of southern Africa (Mucina and Rutherford 2006; Atlas of Namibia Team 2022). The Greater Cape Floristic Region (GCFR) can be divided into the Core Cape Subregion, which corresponds to the Cape Floristic Region (CFR), and the Extra Cape Subregion (ECR), which encompasses the rest of the GCFR (Manning and Goldblatt 2012; Snijman, 2013). (B) Contrasting climatic conditions across southern Africa. Colours indicate the aridity index for the 1970–2000 period (Trabucco and Zomer 2019), with climate classes according to the United Nations Environment Programme (1997). Rainfall seasonality results in a winter-rainfall zone (WRZ), a year-round-rainfall zone (YRZ) and a summer-rainfall zone (SRZ) (Chase and Meadows 2007; Chase et al. 2017). (C) Influence of fog in southern Africa, with shaded areas experiencing ≥ 30 days of fog annually (redrawn from Olivier & van Heerden 2003; Bradshaw & Cowling 2014; Atlas of Namibia Team 2022); the Great Escarpment (dashed line) is a major topographical feature that represents the verge of the southern African plateau, with steep slopes down to the coastal areas. Superimposed is the geographical distribution of the nineCrassula species examined here; data from GBIF (2022), with manual data cleaning for C. ovata and C. multicava to approximate it to their native distribution, based on descriptions by Tölken (1985), van Jaarsveld (2003) and Smith, Crouch & Figueiredo (2017). Only one locality is known for C. ausensis subsp.titanopsis , so all localities for C. ausensis were included in the map.
Figure 2. Habit in the wild of the Crassula species examined in this study. (A) C. multicava subsp.multicava , (B) C. ovata , (C) C. perforata subsp. perforata , (D) C. tecta ,(E) C. fragarioides , (F) C. sericea var.sericea , (G) C. deceptor , (H) C. plegmatoides , (I) C. ausensis subsp. titanopsis .
Photo credits: (A) Craig Peter, iNat ID 33843433; (B) Craig Peter, iNat ID 59494774; (C) Luc Strydom, iNat ID 75803984; (D) Di Turner, iNat ID 22557424; (E) Ismail Ebrahim, iNat ID 16279839; (F) Matt Berger, iNat ID 96923577; (G) Andrew Hankey, iNat ID 11038117; (H) Nick Helme, iNat ID 93580736; (I) Petr Pavelka.
Figure 3. Leaf morphology and macroscopic surface details of the Crassula species examined. (A) C. multicavasubsp. multicava , (B) C. ovata , (C)C. perforata subsp. perforata , (D) C. tecta , (E) C. fragarioides , (F) C. sericea var. sericea , (G) C. deceptor ,(H) C. plegmatoides , (I) C. ausensissubsp. titanopsis .
Figure 4. Microscopic leaf details of the Crassulaspecies examined, showing for each species the leaf surface (left) and a vibratome section (right). Hydathodes can be observed in all species.(A) C. multicava subsp. multicava ; note the white mineral crust on the hydathodes. (B) C. ovata ; note the white mineral crust on the hydathodes. (C) C. perforatasubsp. perforata , margin (top row) and lamina (bottom row); note anthocyanin contents in hydathode sheath cells (top row), and partially removed waxy bloom and absence of hydathodes in the lamina (bottom row).(D) C. tecta ; note clustering of bladder-cell idioblasts. (E) C. fragarioides ; note clustering of papillae. (F) C. sericea var. sericea .(G) C. deceptor ; note eroded epicuticular waxes at the tip of tubercles. (H) C. plegmatoides . (I)C. ausensis subsp. titanopsis ; note clustering of clavate trichomes and anthocyanin contents in hydathode sheath cells. In all images the adaxial side is towards the top.
Figure 5. Microscopic leaf surface details of Crassulaspecies examined with environmental scanning electron microscopy (ESEM).(A) C. multicava subsp. multicava ; note the presence of a mineral crust on the hydathodes (left), which can be removed revealing the water pores (right). (B) C. ovata ; note thick waxy crust on the leaf, which tends to crack (left), and the presence of a mineral crust on and around the hydathodes (right).(C) C. perforata subsp. perforata . (D)C. tecta . (E) C. fragarioides . (F)C. sericea var. sericea . (G) C. deceptor .(H) C. plegmatoides . (I) C. ausensissubsp. titanopsis . Arrowheads indicate hydathode water pores, dashed circles indicate water pore epidermal areas of type I hydathodes.
Figure 6. Anatomy of hydathodes of the Crassula species examined; semi-thin sections of resin-embedded material, stained with toluidine blue. (A) C. multicava subsp.multicava , (B) C. ovata , (C) C. perforata subsp. perforata , (D) C. tecta ,(E) C. fragarioides , (F) C. sericea var.sericea , (G) C. deceptor , (H) C. plegmatoides , (I) C. ausensis subsp. titanopsis . Arrowheads indicate hydathode water pores, “E” indicates epithem, “T” indicates tracheids. In all images the adaxial side is towards the top.
Figure 7. Measurements of contact angle (θC) in the areas of interest for the Crassula species examined (seeTable 2 ). Mean and ± standard deviation are plotted for each species. Wettability classes according to Barthlott et al.(2017).
Figure 8. Water uptake observed in free-hand sections of leaves from drought-stressed and well-watered plants treated with LYCH.(A) C. multicavasubsp. multicava , (B) C. ovata , (C)C. perforata subsp. perforata , (D) C. tecta , (E) C. fragarioides , (F) C. sericea var. sericea , (G) C. deceptor ,(H) C. plegmatoides , (I) C. ausensissubsp. titanopsis . Same leaf zones imaged with long-pass (ex. 480/40 nm; em. 510 nm LP) and band-pass (ex. 470/40 nm; em. 525/50 nm) filter sets, showing LYCH (green). In all images the adaxial side is orientated upwards. See Figs. S2, S3 for fluorescence in untreated samples (controls).
Figure 9. Water uptake in whole leaves of (A) C. multicava subsp. multicava and (B) C. ovata . Adaxial side shown, leaf margin orientated towards the top of the image. Dashed circles indicate approximate area where the droplet of LYCH was applied.