Morphoanatomical leaf traits of herbaceous species raised in a cronosequence of naturally regenerated areas of tropical deciduous forest

Plant survival in semi-arid climates depends on morphological, anatomical, and physiological adjustments that determine survival under limiting environmental conditions. In this study, anatomical and morphological characteristics of three herbaceous species with different growth habits were determined: a tall herb, Mesosphaerum suaveolens (tall), Stachytarpheta sanguinea (short), and Jacquemontia evolvuloides (climbing). Fully expanded leaves were collected from three sites in each of three different natural regeneration periods in a seasonally dry tropical forest. Leaf, specific leaf area, epidermis, cuticle, parenchyma, and mesophyll thicknesses; stomatal and trichome densities were measured. All three species have stomata and trichomes on both leaf surfaces and higher densities on the abaxial surface than the adaxial surface. M. suaveolens and S. sanguinea have unusual leaf morphological and anatomical adjustments, with a larger leaf area in the more open and youngest site, but thicker abaxial and adaxial epidermis and mesophyll in the oldest site which has the closest canopy stratum. J. evolvuloides has more usual adjustments, with a smaller specific leaf area and thinner epidermis and isobilateral parenchyma in the youngest site, being better acclimatized to low water availability and high light incidence. Therefore, M. suaveolens and S. sanguinea have unique acclimatization strategies for different environmental conditions.