Weak co-ordination between vein and stomatal densities in 105 angiosperm tree species along altitudinal gradients in Southwest China

Abstract

Leaf-level water balance, as revealed by a correlation between stomatal density (SD) and vein density (VD), has been reported in some plants. However, the generality of this correlation and how it may be affected by altitude changes are unclear. Here, we investigated whether this balance is maintained across tree species of diverse families along a large altitudinal gradient. We measured leaf area (LA), SD, stomata length (SL), and VD in 105 angiosperm species across two altitudinal ranges, 800–1400 m above sea level (a.s.l.) in tropical montane forests (TMF) and 2000–2600 m a.s.l. in subtropical montane forests (SMF) in Yunnan, South-west China. The average SD was independent of altitude in both regions. Similarly, the average VD within either SMF or TMF was also not significantly different. However, overall, TMF had significantly larger VD and LA but smaller SL than SMF. Vein density was positively correlated with SD across SMF species, with a weaker correlation for TMF species and all species combined. Stomatal length was negatively correlated with SD and VD across all species. Our results extend the leaf water balance theory to diverse angiosperm tree species, and indicate decoupled adaptation of SD and VD in these species along a large altitudinal gradient.

Stable stomatal number per minor vein length indicates the coordination between leaf water supply and demand in three leguminous species

“…The positive correlation between SD and MVD under each light regime affirms their coordination in peanut, which also has been reported in the other species 1, 10, 27–29 . As predicted, the leaflets did not exhibit significant differences in SV under each light regime (Fig.…”

Leaf Venation Variation and Phenotypic Plasticity in Response to Environmental Heterogeneity in Parrotia subaequalis (H. T. Chang) R. M. Hao et H. T. Wei, An Endemic and Endangered Tree Species from China

“…Observations of the leaf venation pattern were carried out according to Zhao et al (2016) [18], with 15 leaf venation characteristics ( Table 2) selected for analysis. Fresh or herbarium leaves were cleared according to Dizeo de Strittmatter (1973) [30] and stained in safranin/80% ethanol.…”

“…Venation properties have been recognized as a type of phenotypic plasticity that is caused by ontogeny. There have been numerous reports on the correlations between leaf vein density and leaf area [15], epidermal cell size [16], stomatal density [17][18][19], stomatal conductance [19], hydraulic conductance [19,20], and photosynthesis [13]. However, variations in leaf venation and leaf vein density under different environmental conditions have not been widely reported until recently [21], especially for endangered species.…”

Water supply and demand remain coordinated during breakdown of the global scaling relationship between leaf size and major vein density

“…Brodribb & Jordan, ; Brodribb et al ., ; McElwain et al ., ), indicating a general relaxation of hydraulic constraints in this family. A weaker correlation may arise when the coordination is rather at the level of total stomata number and vein length per leaf, and thus irrespective of leaf area (Zhao et al ., ), and, from a mechanistic perspective, when there is variation in the degree to which the mechanisms coordinating the development of veins and stomata are exploited (Carins Murphy et al ., ). Maintaining vein and stomatal densities coordinated certainly involves different, sometimes independent developmental processes as illustrated by taxa in which the coordination is passively achieved by modulating leaf size, while in others this coordination is unrelated to leaf expansion (Carins Murphy et al ., ).…”

“…Furthermore, with stomata density determining the maximum rate of photosynthesis and water loss and vein density determining the capacity of water supply in leaves, plants are likely to seek a balance between the two traits during adaptation to different environments. To date, this coordination between vein and stomatal densities has been demonstrated in intra‐ and interspecific comparisons for vein networks that regulate vein density by modifying minor vein branching (Edwards, ; Dunbar‐Co et al ., ; Carins Murphy et al ., ; Brodribb et al ., ; Fiorin et al ., ; Li et al ., ; McElwain et al ., ; but see Zhao et al ., , for the lack of such coordination). However, it is unclear how both traits interact in dicotyledonous vein networks in which changes in vein density are primarily achieved with major veins, namely vein orders 1°–3°.…”