Structural traits of leaf epidermis correspond to metal tolerance in Rumex acetosella populations growing on metal-contaminated soils

The overlooked functions of trichomes: Water absorption and metal detoxication

“…We have identified 37 studies examining metal accumulation in trichomes (Table 2). These studies have been conducted for a wide range of purposes, including for examining plant metal tolerance and detoxication mechanisms (Choi et al, 2001; Čiamporová et al, 2021; Iwasaki & Matsumura, 1999), observing metal distribution in plant leaves (Ager et al, 2003; Lei et al, 2008) and for examining the specific roles of trichomes in plant metal hyperaccumulation (W. Li et al, 2005; Mcnear & Kupper, 2014; Ricachenevsky et al, 2021). In addition, a variety of analytical approaches have been used to investigate the accumulation of metals in the trichomes, including scanning electron microscopy coupled with energy dispersive spectroscopy (SEM‐EDS), synchrotron‐based X‐ray fluorescence microspectroscopy (XFM), nuclear microprobe analysis and confocal microscopy with specific fluorescence dyes (Ager et al, 2003; Broadhurst, Chaney, Angle, Erbe, et al, 2004; Kozhevnikova et al, 2014).…”

“…It is of considerable interest to understand the mechanisms whereby metals accumulate in trichomes. Firstly, it has been found that the basal cells of the trichomes in which metals accumulate are generally connected with the surrounding mesophyll or epidermal cells by plasmodesmata, and that the trichome basal cells are generally further connected with vascular tissues such as bundle sheath extensions—these enable the translocation of metals in or out of the trichomes (Čiamporová et al, 2021; C. Li et al, 2021). Secondly, once the metals have been translocated into the trichome, they must then be detoxified.…”

“…A. marina , Rumex acetosella and Nicotiana tabacum are the only three species where glandular trichomes have been found to accumulate metals. Interestingly, the glandular trichomes of A. marina and N. tabacum have also been found to excrete metals from glandular trichomes, with enhanced Ca concentrations promoting this excretion in N. tabacum (Choi et al, 2001; Čiamporová et al, 2021; Macfarlane & Burchett, 2000). Across the 33 plant species, the morphology and structure of the trichomes involved in metal accumulation vary greatly, including trichomes that are ‘Y’ shaped, stellate, dendritic, simple branch shaped and ‘T’ shaped (Table 2 and Figure 5).…”

“…In addition, it has been found that trichome density can increase greatly when plants are under metal stress. For example, Azmat et al (2009) found that the trichome density of Phaseolus mungo and Lens culinaris increased after exposure to high concentrations of Pb, Choi et al (2001) found that the trichome density of tobacco increased upon Cd stress and Čiamporová et al (2021) found that the density of glandular trichomes of R. acetosella increased under Zn and Cu stress. In this regard, it is likely that trichomes are part of plant's stress‐response system, with an increase in trichome density under various stresses, including metal stress (C. Li et al, 2017).…”

“…We have identified 37 studies examining metal accumulation in trichomes (Table 2). These studies have been conducted for a wide range of purposes, including for examining plant metal tolerance and detoxication mechanisms (Choi et al, 2001;Čiamporová et al, 2021;Iwasaki & Matsumura, 1999), observing metal distribution in plant leaves (Ager et al, 2003;Lei et al, 2008) microscopy with specific fluorescence dyes (Ager et al, 2003;Kozhevnikova et al, 2014).…”