Quantitative analyses and models are required to connect a plant’s cellular organisation with its metabolism. However, quantitative data are often scattered over multiple studies, and finding such data and converting them into useful information is time-consuming. Consequently, there is a need to centralise the available data and to highlight the remaining knowledge gaps. Here, we present a step-by-step approach to manually extract quantitative data from various information sources, and to unify the data format. First, data from Arabidopsis leaf were collated, checked for consistency and correctness and curated by cross-checking sources. Second, quantitative data were combined by applying calculation rules. They were then integrated into a unique comprehensive, referenced, modifiable and reusable data compendium representing an Arabidopsis reference leaf. This atlas contains the metrics of the 15 cell types found in leaves at the cellular and subcellular levels.

To study the impact of plant density on Chenopodium quinoa (c.v. CICA-17) achene yield and its relationship with morphology, leaf anatomy and gas exchange in the absence of water stress, field trials were conducted at 1995 m asl in Northwestern Argentina. Two plant densities were evaluated; low density (LD) 7.2 plants/m (120 240 pl/ha) and high density (HD) 27.9 plants/m (465 930 pl/ha). HD treatment caused light competition, inducing morphological and anatomical changes in Quinoa plants. Plants grown under HD conditions showed decreases in plant height and stem diameter, lower stomatal dimensions and densities, and thinner leaf blades. Compensation strategies such as increases in specific leaf area and a higher number chloroplasts per palisade cell were observed, nevertheless these changes did not fully compensate C absorption and gas exchange limitations, therefore limiting the uptake of N and P and resulting in a 53.2% lower yield of HD compared to LD. Considering the ability of quinoa plants to change its morphology and anatomy, further studies with intermediate plant densities are necessary in order to determine if it is possible to achieve higher yields and to increase the efficiency in the use of the resources.

Leaf anatomical and carbon isotope ratio (δ13C) data from previous studies suggest that the species of the Melastomataceae perform C3 photosynthesis and that leaf anatomical features of some epiphytic taxa resemble the characteristics found in CAM plants. The δ13C values of 67 species of neotropical Melastomataceae (including epiphytes) were obtained from herbarium material deposited at the California Academy of Sciences for assessing the presence of the CAM pathway. The δ13C values obtained from leaves (−23.4‰ to −34.5‰) were congruent with C3 photosynthesis (< −20‰), and the δ13C data from terrestrial (56 samples) and epiphytic species (11 samples) were not statistically different. Our results suggest that CAM photosynthesis is not found in neotropical Melastomataceae. The leaf anatomical features found in some species of Melastomataceae represent adaptations to cope with water stress and are not necessarily correlated with CAM photosynthesis. Photosynthetic pathways can be assessed with the use of leaf anatomical and δ13C data, but further biochemical assays are warranted to corroborate the absence of the CAM pathway in the Melastomataceae.

Kalanchoe pinnata (Lamarck) Persoon (Crassulaceae) (air plant, miracle leaf) is popularly used to treat gastrointestinal disorders and wounds. Recently, the species was tested to treat cutaneous leishmaniasis with successful results. This medicinal activity was associated with the phenolic fraction of the plant. Blue light induces biosynthesis of phenolic compounds and many changes in anatomical characteristics. We studied the effects of supplementary blue light on the leaf morphology of in vitro K. pinnata. Plants cultured under white light (W plants) only and white light plus blue light (WB plants) show petioles with plain-convex section, amphistomatic leaf blades with simple epidermis, homogeneous mesophyll with densely packed cells, and a single collateral vascular bundle in the midrib. W plants have longer branches, a larger number of nodes per branch, and smaller leaves, whereas WB plant leaves have a thicker upper epidermis and mesophyll. Leaf fresh weight and leaf dry weight were similar in both treatments. Phenolic idioblasts were observed in the plants supplemented with blue light, suggesting that blue light plays an important role in the biosynthesis of phenolic compounds in K. pinnata.

Nine species of Cyrtandra (Gesneriaceae) are recognized in Peninsular Malaysia. Three (C. cupulata, C. pendula and C. wallichii) are common and occur more or less throughout the area; C. pendula is also recorded from Singapore. Four (C. dispar, C. gimlettei, C. patula and C. suffruticosa) have more restricted distributions, and two (C. lanceolata and C. stonei) are local endemics. Three species and one variety originally described by Ridley are here reduced to synonymy: C. barbata (=C. cupulata), C. falcata (=C. suffruticosa) and C. rotundifolia (=C. pendula), and C. cupulata var. minor (=C. cupulata). Keys for fieldwork and herbarium use are presented and general information is provided. The appendix by M.H. Bokhari contains descriptions of leaf anatomy for eight of the nine species recognized and a key based on anatomical characters.

Changes in morphological and anatomical leaf characteristics of woody plant species along an altitudinal gradient as well as between a late-successional and mature upper montane rain forest were examined. For leaf size, the Raunkiaer-Webb classification system was applied. The mature-forest transect comprised eight plots of 0.1 ha between 2300 and 3300 m asl, the successional-forest transect, four plots between 2400 and 2750 m asl. The latter comprised structurally heterogeneous vegetation patches. For each plot the proportions of leaf size classes and of the different categories of leaf shape, margin, and apex were calculated. Leaf size and the proportion of drip-tips decreased with increasing elevation. Serrate leaf margins were more prominent at higher elevations. Stomatal density, leaf thickness and related anatomical characteristics did not show significant trends. Differences between the mature and successional forest plots were generally slight. The advanced age of the successional forest probably led to a convergent development of leaf characteristics.

This study compares leaf anatomy, chlorophyll content and photosynthetic induction rates for seedlings of five dipterocarp species growing both by a path and in the understorey of a Bornean heath forest. Hemispherical photographs were used to estimate the light level. Although three of the five species showed significantly higher photosynthetic capacity in high light conditions, there were no significant within-species differences in induction rates. Average induction times to reach 50% (T50%) and 90% (T90%) of maximum photosynthetic rate (Amax) were about 1.5 and 9 min for Shorea pachyphylla. In contrast, these were 18 and 37 min respectively for Dipterocarpus borneensis, and 12 and 25 min for Shorea multiflora. Intermediate values were recorded for Hopea pentanervia and Cotylelobium burckii. There was an overall weak and negative correlation of induction rate with stomatal density. Three species showed more rapid induction loss in their leaves from the path edge vs. the understorey. The results suggest that photosynthetic acclimation can influence some aspects of a leaf's dynamic response to sunflecks, such as Amax and induction loss, while not affecting overall induction rates. This study also shows significant differences among diptero carp species in photosynthetic capacity, induction responses and leaf structure, and in acclimation on these traits.

The relationships of foliage assimilation capacity per unit area (PPmax) with leaf dry mass per unit area (LMA) and nitrogen content per unit area (NP) differ between species and within species grown in different habitats. To gain a more mechanistic insight into the dependencies of PPmax on LMA and NP, this literature study based on 597 species from a wide range of earth biomes with woody vegetation examines the relations between leaf photosynthetic capacity and the components of LMA (leaf density (D, dry mass per volume) and thickness (T)), and also the correlations of D and T with leaf nitrogen content and fractional leaf volumes in different tissues. Across all species, PPmax varied 12-fold and photosynthetic capacity per unit dry mass (Pmmax) 16-fold, NP 12-fold, and nitrogen per unit dry mass (Nm) 13-fold, LMA 46-fold, D 13-fold, and T 35-fold, indicating that foliar morphology was more plastic than foliar chemistry and assimilation rates. Although there were strong positive correlations between PPmax and NP, and between Pmmax and Nm, leaf structure was a more important determinant of leaf assimilation capacities. PPmax increased with increasing LMA and T, but was independent of D. By contrast, Pmmax scaled negatively with LMA because of a negative correlation between Pmmax and D, and was poorly related to T. Analysis of leaf nitrogen and tissue composition data indicated that the negative relationship between D and Pmmax resulted from negative correlations between D and Nm, D and volumetric fraction of leaf internal air space, and D and symplasmic leaf fraction. Thus, increases in leaf density bring about (1) decreases in assimilative leaf compounds, and (2) extensive modifications in leaf anatomy that may result in increases in intercellular transfer resistance to CO2. Collectively, (1) and (2) lead to decreased Pmmax, and also modify PPmax versus LMA relationships.

Both within and between species, leaves of plants display wide ranges in structural features. These features include: gross investments of carbon and nitrogen substrates (e.g. leaf mass per unit area); stomatal density, distribution between adaxial and abaxial surfaces, and aperture; internal and external optical scattering structures; defensive structures, such as trichomes and spines; and defensive compounds, including UV screens, antifeedants, toxins, and silica abrasives. I offer a synthesis of selected publications, including some of my own. A unifying theme is the adaptive value of expressing certain structural features, posed as metabolic costs and benefits, for (1) competitive acquisition and use of abiotic resources (such as water, light and nitrogen) and (2) regulation of biotic interactions, particularly fungal attack and herbivory. Both acclimatory responses in one plant and adaptations over evolutionary time scales are covered where possible. The ubiquity of trade-offs in function is a recurrent theme; this helps to explain diversity in solutions to the same environmental challenges but poses problems for investigators to uncover numerous important trade-offs. I offer some suggestions for research, such as on the need for models that integrate biotic and abiotic effects (these must be highly focused), and some speculations, such as on the intensity of selection pressures for these structures.

The relationships between leaf structure, nitrogen concentration and CO2 assimilation rate (A) were studied for 14 grass species grown in the laboratory under non-limiting nutrient conditions. Structural features included leaf thickness and density, and the proportion of leaf volume occupied by different types of tissue (mesophyll, epidermis, vessels and sclerenchyma). Relationships were assessed for data expressed per unit leaf area and fresh mass. The latter was found to be closely related to leaf volume, which allowed us to use A per unit leaf fresh mass (Afm) as a surrogate of A per unit leaf volume. Assimilation rate per unit leaf area (Aa) was positively correlated with leaf thickness and with the amount of mesophyll per unit leaf area; the relationship with leaf nitrogen content per unit area was only marginally significant. Afm was negatively correlated with leaf thickness and positively with fresh mass-based leaf organic nitrogen concentration. A multiple regression involving these two variables explained 81% of the variance in Afm. The value of Afm was also significantly related to the proportion of mesophyll in the leaf volume, but surprisingly the correlation was negative. This was because thin leaves with high Afm and nitrogen concentration had proportionally more mechanically supportive tissues than thick ones; as a consequence, they also had a lower proportion of mesophyll. These data suggest that, in addition to leaf nitrogen, leaf thickness has a strong impact on CO2 assimilation rate for the grass species studied.

Oxygen evolution was measured from mesophyll tissues in spinach leaves using a photoacoustic technique. The photosynthetic capacity of individual cell layers was measured by directing microscopic beams of light, 40 μm wide, to cells exposed within a leaf cross section. The resulting profile for oxygen-evolution potential was relatively flat, indicating a uniform capacity for photosynthesis in leaf mesophyll tissues. Two experimental approaches were used to estimate the photosynthetic performance of individual mesophyll cell layers when white light was applied to the adaxial leaf surface. These experiments indicated that oxygen was produced relatively uniformly across the mesophyll and that oxygen evolution increased with irradiance of the white light applied to the leaf surface. The measured profiles for oxygen evolution and capacity are flatter than previous measurements of profiles of fixed carbon and estimates of profiles for absorbed light within spinach leaves.

Influence of habitat on physiological and structural characteristics was investigated for broad-leaved tropical monocotyledons in the genus Heliconia (Heliconiaceae). Seven species were selected from three different light regimes, enabling an analysis of the extent to which this genus has adapted its photosynthetic strategies and morphological characteristics to different daily photon flux densities (PFD). Predictably, light response curves showed a clear gradient with respect to light saturation and rates of maximum net assimilation (Amax). Heliconia latispatha, an open site species, showed saturation at higher PFD (1400 μmol m−2 s−1) and higher Amax (14–16 μmol m−2 s−1) than H. mathiasiae, a forest edge species (PFD 1000 μmol m−2 s−1; Amax 7.5–8.5 μmol m−2 s−1) and H. irrasa of deep-shade forest understorey (PFD 250 μmol m−2 s−1; Amax 3.5 mol m−2 s−1). Leaf blade areas were largest in open sites, and leaf specific mass was also significantly higher, but leaf support efficiency was highest in understorey species. Species in open sites had thicker leaves with more chlorenchyma, whereas deep-shade species had very thin leaves and low stomatal densities. These rapidly growing herbaceous perennials appear to allocate much of their above-ground biomass to leaf tissues and have a relatively low investment in support tissues. This contrasts with understorey palms, in which leaf form and structural investment has been interpreted as a trade-off between economy and protection against tissue loss from falling branches. Presence of below-ground rhizomes in Heliconia may provide the key to this difference.

We studied interspecific and ontogenetic relationships between the size of a leaf and the primary diameter of the internode bearing it. Although these two variables are known to be strongly correlated across species, the form of this relationship has not been studied. In a re-analysis of published data on interspecific comparisons of 69 temperate tree species, we showed the existence of a strong relationship between twig cross-sectional area (before secondary growth) and surface area of leaves borne by it, within each of three morphological groups, deciduous angiosperms, evergreen angiosperms, and gymnosperms. Within each of these groups, this relationship is isometric: across species, primary cross-sectional area of the stem increases proportionally with leaf surface area. When we consider the relationship between the cross-sectional area of a twig and the surface area of one leaf borne by it, the y-intercepts for this relation are different for the three groups. However, when total leaf surface area per first-year shoot is considered, no differences remained between gymnosperms and evergreen angiosperms, but deciduous angiosperms continued to be distinct. This difference between deciduous and evergreen groups could be due to differences in leaf volume (evergreen species have thicker leaves than deciduous) or in traits related to a trade-off between life span of leaves and their physiological behaviour.

We present results of the first quantitative study of the relationship between leaf size and primary diameter of the stem during ontogeny. Both these parameters increase during development of the plant from seedling to adult. For the four tree species examined, the relationship between primary cross-sectional area of the stem and leaf surface area is also isometric.

These results bear on a functional interpretation of the relationship between leaf and stem dimensions, suggesting that vascular supply is directly proportional to the requirements of leaves supported by the stem.