INVESTIGATIONS OF NORTH AMERICAN CYCADEOIDS: POLLINATION MECHANISMS IN CYCADEOIDEA

Wind was at first thought of as the chief pollinating mechanism in Cycadeoidea because of the open angiosperm-flower-like reconstruction of the cone presented by G. R. Wieland in 1906. Selfing seemed a more likely possibility after Delevoryas reinterpreted the cone as a closed structure in 1963. However, the existence of what was considered to be a dioecious group of species made it impossible to consider selfing as ubiquitous throughout the cycadeoids. Furthermore, only ovule-bearing trunks of the species considered to be dioecious were known; no corresponding trunks bearing exclusively microsporangiate cones had ever been found. Recent investigations of a trunk of the type heretofore considered as representative of the dioecious species have revealed that these cones were actually bisporangiate. The discovery that the bisporangiate condition was normal in the cycadeoids eliminates much of the confusion in understanding the system of pollination and allows selfing to be considered the chief means of pollination. Outcrossing probably occurred in very low frequency and could have been the result of a chance wind pollination or of a set of interactions between the cycadeoids and an unidentified animal. Determining the nature of the system of pollination in the cycadeoids makes it possible to speculate on the population structure and evolutionary potential of this important Mesozoic group of plants.     

A new Neocalamites (Sphenophyta) with prickles and attached cones from the Upper Triassic of China

Remains of the extinct sphenophyte (horsetail) Neocalamites are most widespread in the Middle–Upper Triassic and are typically represented by stem and leaf fragments. Here we report on spectacular new finds of Neocalamites from the Late Triassic Yangcaogou Formation in Liaoning Province, China that include bedding surfaces dominated by nearly complete aerial stems with attached leaf whorls and rare bractless cones. They reveal a monopodial growth habit for the stems, which are covered with downward projecting prickles that probably provided protection against herbivores. These features provide the basis for a new proposed species, Neocalamites horridus. The nodes bear whorls of very long leaves mainly free to their bases, and one specimen bears an attached cone on a long peduncle. Identical dispersed cones have also been recovered. The leaves of adjacent monopodial stems most likely interlocked to support growth in large stands akin to the role now played by branches in large modern Equisetum species. The new Chinese Neocalamites is among the most confidently reconstructed species, and indicates a greater diversity of sphenophyte morphology during the Mesozoic than previously realized.     

Recovery from Cucumber Mosaic Virus Infection for ‘Calwonder’ Bell Pepper Plants Does not Counter Negative Impacts on Plant Growth

Cucumber mosaic virus (CMV) accumulation in leaves and stems of infected bell pepper plants at specific symptom stages was evaluated with an emphasis on the transition from full infection to recovery from Cucumber mosaic disease. Four symptom phases occurred in successive order, designated chlorosis (leaves 6–8), mosaic (leaves 9–11/12), leaf distortion (first series of leaves on secondary and tertiary branches) and recovery (progressive recovery with newly emerging leaves in tertiary and younger branches). In situ detection of CMV in leaf tissues revealed widespread occurrence in leaves expressing chlorosis and mosaic symptoms but reduced, localized occurrence in leaves in the recovery phase. Similarly, CMV accumulated to high levels throughout stems expressing chlorosis and mosaic symptoms but with dramatically reduced levels for plants in the recovery symptom phase. Stunting of internodes occurred at all locations above the inoculated leaves by the first expression of systemic symptoms, suggesting an impact on stem growth in response to initial virus invasion of young developing tissues of the stem. Despite the recovery from CMV infection, plant growth was negatively impacted early in the infection process and remained so through the course of the experiment.     

Clumped distribution of oak leaf miners between and within plants

Leaf miners typically show non-random distributions both between and within plants. We tested the hypothesis that leaf miners on two oak species were clumped on individual host trees and individual branches and addressed whether clumping was influenced by aspects of plant quality and how clumping and/or interactions with other oak herbivores affected leaf-miner survivorship. Null models were used to test whether oak herbivores and different herbivore guilds co-occur at the plant scale. Twenty individual Quercus geminata plants and 20 Quercus laevis plants were followed over the season for the appearance of leaf miners and other herbivores, and foliar nitrogen, tannin concentration, leaf toughness and leaf water content were evaluated monthly for each individual tree. The survivorship of the most common leaf miners was evaluated by following the fate of marked mines in several combinations that involved intra- and inter-specific associations. We observed that all leaf miners studied were clumped at the plant and branch scale, and the abundance of most leaf-miner species was influenced by plant quality traits. Mines that occurred singly on leaves exhibited significantly higher survivorship than double and triple mines and leaves that contained a mine or a leaf gall and a mine and damage by chewers exhibited lowest survivorship. Although leaf miners were clumped at individual host trees, null model analyses indicated that oak herbivores do not co-occur significantly less than expected by chance and there was no evidence for biological mechanisms such as inter-specific competition determining community structure at the plant scale. Thus, despite co-occurrence resulting in reduced survivorship at the leaf scale, such competition was not strong enough to structure separation of these oak herbivore communities.     

Aphids do not attend to leaf colour as visual signal, but to the handicap of reproductive investment

The evolution of visual warning signals is well known in animals but has received scant attention in plants. The coevolutionary hypothesis is the most influential hypothesis on warning signals in plants proposing that red and yellow leaf colours in autumn signal defensive strength to herbivores. So far, evidence in support of the hypothesis, which assumes a coevolutionary origin of autumnal leaf colours, is correlative and open to alternative explanations. We therefore tested the coevolutionary hypothesis experimentally by colouring the leaves either red or green of same-aged mountain ash (Sorbus aucuparia) individuals. We monitored the response of winged aphids to leaf colour using insect glue on branches with natural and artificial leaf colours in each individual. In contrast to the prediction of the coevolutionary hypothesis, aphid numbers did not differ between the individuals with artificial green or artificial red leaves. Likewise, at the within-plant level, aphids did not colonize branches with natural green leaves preferentially. However, we suggest that plants emitted warning signals because aphids colonized the hosts non-randomly. We found a strong positive correlation between aphid numbers and fruit production, suggesting an allocation trade-off between investment in plant defence and reproduction. Our study demonstrates that aphids use warning signals or cues in host selection, probably volatiles, but that they did not use leaf colour.     

Correlated evolution of leaf shape and trichomes in Begonia dregei (Begoniaceae)

Structural features of leaves, including size, shape, and surfaces, vary greatly throughout the plant kingdom. In both functional and phylogenetic analyses of leaves, the various morphological aspects are often considered independently of each other, although it is likely that many combinations of features do not occur at random due to either functional constraint or genetic correlation. The distribution of variation in leaf morphology in the highly variable Begonia dregei species complex was examined in natural populations and in F(2) offspring from a cross between plants from two populations. Leaf shape was quantified using several morphometric measures, and trichomes on leaves were counted and measured. Correlations between leaf shape and the numbers and size of trichomes were examined. There were significant correlations between the shapes of leaves and the presence, number, and size of trichomes among populations and in hybrid plants. Deeply incised leaves had larger numbers of longer trichomes at the sinuses. Higher numbers of trichomes on upper leaf surfaces occurred together with trichomes at the petiole and on the abaxial surface. The potential for independent evolution of leaf shape and trichomes in this group is limited. Hypotheses to explain the correlated development of leaf shape and trichomes are discussed.     

INVESTIGATIONS OF NORTH AMERICAN CYCADEOIDS: MONANTHESIA

Delevoryas , Theodore . (Yale U., New Haven, Conn.) Investigations of North American cycadeoids: Monanthesia. Amer. Jour. Bot. 46(9): 657–666. Illus. 1959.—A study of the cycadeoid trunks from the Upper Cretaceous Mesaverde formation of northwestern New Mexico, which are in the collections of the Peabody Museum of Natural History, Yale University, has been completed. These plants had columnar trunks with persistent leaf bases and a cone in the axil of every leaf. The vascular supply of the cone is derived from the fusion of two cortical bundles which arise from two leaf traces, neither of which supplies the subtending leaf. Enough difference appears to exist between these forms and Cycadeoidea to warrant a separate generic designation. Monanthesia is the generic name used, and the single species, M. magnifica, is considered to include all the stems from the New Mexico localities. The pattern of vascularization of cones seems to suggest that they are foliar structures and that Monanthesia is probably a more advanced form than Cycadeoidea.     

Some aspects of the morphology and distribution of Microsoriurn linguaeforrne (Polypodiaceae)

Microsorium linguaeforme is reported for the first time from India. Its rhizome is slender, much elongated with a highly dissected stele and leaf gaps in a single median dorsal row. The characteristic branching pattern is a modification of the common pattern in Polypodiaceae, resulting from the displacement of leaf-associated branches and the precocious development of the most basal secondary branch of each primary branch. The first two or three leaves of juvenile plants have no associated branches; thereafter, abaxially-originating traces t o solitary branches are progressively displaced so that the branch trace is close to the preceding leaf trace. Stomata of adult leaves are Copolomesoperigenous and of juvenile leaves Eupolomesoperigenous. The spores are monolete and with a smooth exine. Spore germination is of the Vitiariatype and prothallial development of the Kauliniatype. It is concluded that M. linguaeforme is closely allied to Leptochilus and is probably parental to it.     

INVESTIGATIONS OF NORTH AMERICAN CYCADEOIDS: TRUNKS FROM WYOMING

Delevoryas , Theodore . (University of Illinois, Urbana.) Investigations of North American cycadeoids: trunks from Wyoming . Amer. Jour. Bot. 47(9): 778–786. Illus. 1960.—A study was undertaken of the cycadeoid trunks from Wyoming to more fully understand the morphology and evolutionary significance of these trunks and to determine the validity of the genus Cycadella. The stem named Cycadeoidea (or Cycadella) utopiensis is not the same morphologically as those from Carbon County, Wyoming, and because of its unknown source, it is not a reliable specimen for the study of cycadeoids from the Morrison formation. The Morrison, Carbon County specimens included in Ward's genus Cycadella were shown to have trunk structure, leaf bases, and cones like those in Cycadeoidea. The cone vascular bundle is derived from a fusion of 4 leaf traces. From the fused bundle complex, 4 leaf traces are separated farther out in the cortex, and 1 of these supplies the subtending leaf. In spite of the relatively complex pattern of cone trace formation, there does not seem to be any significant means of distinguishing specimens called Cycadella from the more common Cycadeoidea. Furthermore, it is evident that the genus Cycadeoidea represents a fairly homogeneous group with a wide geographic and geologic range. Pattern of formation of cone traces is interpreted as possible further evidence for regarding cycadeoid cones as portions of foliar systems.     

Masting in whitebark pine (Pinus albicaulis) depletes stored nutrients

? In masting trees, synchronized, heavy reproductive events are thought to deplete stored resources and to impose a replenishment period before subsequent masting. However, direct evidence of resource depletion in wild, masting trees is very rare. Here, we examined the timing and magnitude (local vs individual-level) of stored nutrient depletion after a heavy mast event in Pinus albicaulis. ? In 2005, the mast year, we compared seasonal changes in leaf and sapwood nitrogen (N) and phosphorus (P) concentrations and leaf photosynthetic rates in cone-bearing branches, branches that never produced cones, and branches with experimentally removed cones. We also compared nutrient concentrations in cone branches and branches that had never had cones between 2005 and 2006, and measured tree ring width and new shoot growth during 2005. ? During the mast year, N or P depletion occurred only in tissue fractions of reproductive branches, where photosynthetic rates were reduced. However, by the end of the following year, nutrients were depleted in all branches, indicating individual-level resource depletion. New shoot and radial growth were not affected by masting. ? We provide direct evidence that mast events in wild trees deplete stored nutrients. Our results highlight the importance of evaluating reproductive costs over time and at the individual level.     

Impact of plant architecture versus leaf quality on attack by leaf-tying caterpillars on five oak species

Because shelter-building herbivorous insect species often consider structural features of their host plants in selecting construction sites, their probability of attack is likely to be a function of some combination of plant architectural traits and leaf quality factors. We tested the hypothesis that plant architecture, in the form of the number of touching leaves, influences interspecific variation in attack by leaf-tying caterpillars in five species of sympatric Missouri oaks (Quercus). We compared colonization on control branches, in which both architecture and leaf quality were potentially important, with colonization on experimental branches for which we controlled for the effects of architecture by creating equal numbers of artificial ties. Colonization of artificial ties was highly correlated with natural colonization on neighboring control branches, suggesting that leaf quality factors and not architecture influenced interspecific variation in attack by leaf-tying caterpillars. Of the leaf quality factors measured (water, protein-binding capacity, nitrogen, specific leaf area, pubescence, and toughness), nitrogen was the most explanatory. With the exception of white oak, natural leaf tie colonization was positively correlated with nitrogen availability (ratio of nitrogen to protein-binding capacity), and negatively correlated with protein-binding capacity of leaf extracts. Both host plant species and subgenus oak influenced the community composition of leaf-tying caterpillars and the non-tying symbionts colonizing the ties. Host plant differences in leaf nitrogen content were positively correlated with pupal weight of one of two caterpillar species reared on all five host plant species. Thus, interspecific differences in nitrogen, nitrogen availability, and protein-binding capacity of leaf extracts are the best predictors at this time of interspecific differences in attack by leaf-tying caterpillars, in turn affecting their success on individual host plants in the laboratory.     

A new species of the extinct genus Austrohamia (Cupressaceae s.l.) in the Daohugou Jurassic flora of China and its phytogeographical implications

Abstract A new conifer, Austrohamia acanthobractea, sp. nov., is described from the Jurassic Daohugou flora, Inner Mongolia Autonomous Region, China. The material consists of impressions represented by well‐preserved leafy twigs and branches as well as ovulate cones. Leafy shoots with at least two orders of branching; ultimate branchlets alternate or sub‐opposite with helically arranged leaves, decurrent at base with distal rounded tip; dorsiventrally flattened and univeined. Ovuliferous cones elliptical, less than 1 cm long, terminally borne on ultimate and penultimate branches, composed of helically arranged bracts with ovules disposed on their adaxial surfaces. The presence of similar, if not identical taxa, on both sides of the Pacific indicates the cosmopolitan distribution of primitive Cupressaceae between East Asia (Eurasia) and South America in the Pangaea.     

Leaf development of the ostrich fern Matteuccia struthiopteris (L.) Todaro

The timing of emergence of the three different leaf types of Matteuccia struthiopteris is described from plants sampled over the course of a growing season. Vegetative leaves were first to appear, followed five weeks later by sporophylls and cataphylls. Leaf number and type, and total leaf dry weight per plant were assessed in weekly transects. Vegetative fronds contributed the most to total leaf dry weight, which increased during the first four weeks, and then remained constant for the remainder of the season. Cataphylls, although numerous by the end of the season, contributed little weight. Sporophylls occurred on the widest plants with the most vegetative leaves and greatest leaf weight, whereas cataphylls occurred on most plants except the smallest. Experimentally defoliated plants were re-examined in late summer. Following initial harvest, plants often produced a second smaller set of leaves. These were restricted to vegetative leaves and cataphylls. Ability to reissue leaves, especially vegetative fronds, declined very quickly after the first few weeks in the growing season. Defoliated plants draw on the extensive reservoir of developing leaves which are found on the rhizome, thus possibly diminishing the ability of the plant to withstand regular harvesting of the young fronds for food. Individual leaves were tagged and measured over the growing season. Non-linear regression curves fitted to the growth data for the three types of leaves indicate that growth was described best by a monomolecular growth curve for the vegetative and fertile fronds. Cataphyllar growth could be described equally well by either a monomolecular or a logistic function.     

Architecture and growth of an annual plant <Emphasis Type="Italic">Chenopodium album</Emphasis> in different light climates

Light climates strongly influence plant architecture and mass allocation. Using the metamer concept, we quantitatively described branching architecture and growth of Chenopodium album plants grown solitarily or in a dense stand. Metamer is a unit of plant construction that is composed of an internode and the upper node with a leaf and a subtended axillary bud. The number of metamers on the main-axis stem increased with plant growth, but did not differ between solitary and dense-stand plants. Solitary plants had shorter thicker internodes with branches larger in size and number than the plant in the dense stand. Leaf area on the main stem was not different. Larger leaf area in solitary plants was due to a larger number of leaves on branches. Leaf mass per area (LMA) was higher in solitary plants. It did not significantly differ between the main axis and branches in solitary plants, whereas in the dense stand it was smaller on branches. Dry mass was allocated most to leaves in solitary plants and to stems in the dense stand in vegetative growth. Reproductive allocation was not significantly different. Branch/main stem mass ratio was higher in solitary than dense-stand plants, and leaf/stem mass ratio higher in branches than in the main axis. Nitrogen use efficiency (NUE) (dry mass growth per unit N uptake) was higher and light use efficiency (LUE) (dry mass growth per unit light interception) was lower in the plant grown solitarily than in the dense stand.     

Gender performance in a cultivated cohort of the cycad Zamia integrifolia (Zamiaceae)

A progeny of the native Florida cycad Zamia integrifolia grown from seeds planted in 1986 was monitored until 1995 to record mortality and the nature and time of expression of primary and secondary sex characters. In addition to gender-specific cone morphologies, males and females differed in secondary sex characters such as age at first cone production, frequency of cone production, mean cone numbers in second and later coning episodes, and, in older plants, mean leaf and branch numbers. Gender differences expressed themselves at different stages in the life history: their nature and extent varied during the years following sexual maturation. By 1995, 46% of the plants in the progeny had died, most of them before producing cones. Prior to 1988 the mean leaf number of plants that died did not differ from that of survivors, but the mean leaf number of plants dying between 1988 and 1989 was 0.4 times that of the survivors during that period, suggesting reduced vigor prior to death. Mean age at first cone production was 5.8 yr for males and 6.6 yr for females. Mean dry masses of individual male cones increased between the first and second coning episodes, but not between the second and third coning episodes. Mean dry masses of the entire cone crop of individual males increased through the third coning episode due to an increase in mean cone number per episode, but mean cone number was unchanged between the third and fourth coning episodes. Mean dry mass of unpollinated female cones did not change between the first and second coning episodes; mean cone numbers did not change between the first and third coning episodes. After the first coning episode, males produced higher mean cone numbers than females. By 1995, the mean dry mass of an individual male's cone crop was greater than that of a female. Coning frequency of males was 1.7 times greater than that of unpollinated females, suggesting a gender difference in the genetic control of coning frequency. Coning frequency of females pollinated 1 or 2 yr previously was reduced compared with that of unpollinated females. Cone production did not affect subsequent leaf production by either gender. Mean leaf numbers increased in some years and not in others. Mean leaf numbers of males and females did not differ prior to cone production. After cone production mean leaf numbers of males were greater than of females. Mean age of males producing first branches was 6.3 yr, with a mean of 2.5 first branches per plant. Mean age of females producing first branches was 7.7 yr, with a mean of 2.5 first branches per plant. By 1995 the mean branch number of males was 5.7 per plant and of females was 2.7 per plant. Between 1993 and 1995 the mean branch number of males and females increased incrementally, but mean leaf numbers did not change. In early years of branching, leaf number increased with branch number; higher mean leaf numbers of males of an age class thus reflected their earlier branching. Males produced first cones earlier than females. Since branch production was associated with cone production, higher branch numbers of males in an age class reflected their earlier first cone production. In 1995 the sex ratio of known males and females in the progeny was 1:1, with a few individuals not having produced cones by that year.     

Leaf development of the ostrich fern Matteuccia struthiopteris (L.) Todaro

The timing of emergence of the three different leaf types of Matteuccia struthiopteris is described from plants sampled over the course of a growing season. Vegetative leaves were first to appear, followed five weeks later by sporophylls and cataphylls. Leaf number and type, and total leaf dry weight per plant were assessed in weekly transects. Vegetative fronds contributed the most to total leaf dry weight, which increased during the first four weeks, and then remained constant for the remainder of the season. Cataphylls, although numerous by the end of the season, contributed little weight. Sporophylls occurred on the widest plants with the most vegetative leaves and greatest leaf weight, whereas cataphylls occurred on most plants except the smallest. Experimentally defoliated plants were re-examined in late summer. Following initial harvest, plants often produced a second smaller set of leaves. These were restricted to vegetative leaves and cataphylls. Ability to reissue leaves, especially vegetative fronds, declined very quickly after the first few weeks in the growing season. Defoliated plants draw on the extensive reservoir of developing leaves which are found on the rhizome, thus possibly diminishing the ability of the plant to withstand regular harvesting of the young fronds for food. Individual leaves were tagged and measured over the growing season. Non-linear regression curves fitted to the growth data for the three types of leaves indicate that growth was described best by a monomolecular growth curve for the vegetative and fertile fronds. Cataphyllar growth could be described equally well by either a monomolecular or a logistic function.     

Changes in eco-morphological parameters of alpine plants' leaves as an effect of fertilization

Plants growing on rich soil usually have thin leaves with large specific leaf area. On the other hand, at intraspecific level; soil fertilization results in leaves size increasing which, in turn, can lead to reduction in specific leaf area. To what extent soil fertilization implies only leaves increasing in size and does not affect other eco-morphological characteristics is a question that is still open. To assess coherence between plants intraspecific reactions to changes in soil richness and general tendencies in changes of leaves parameters in communities with different productivity, an experiment has been conducted in alpine plant communities of the north-western Caucasus. Changes in leaf traits are studied in four types of alpine plant communities after long term application of mineral nutrients (NP and lime treatment). It is shown that in all species, except legume Hedysarum caucasicum, fertilization results in size leaf characteristics (leaf area, wet and dry mass) increase. Specific leaf area appears to decrease in plants inhabiting alpine heathlands and increase in plants inhabiting alpine snow beds and in dominant species of Geranium-Hedysarum meadows, Geranium gymnocaulon. After correction of specific leaf area that accounts for changes in leaf size, it becomes discernable that in most species the increase in leaf area per se results in specific leaf area reduction while changes in leaf structure under influence of fertilization leads to this trait increasing. Those species demonstrating the increase in specific leaf area as an effect of fertilization, also gain more in terms of biomass.     

Developmental process of sun and shade leaves in Chenopodium album L.

The authors’ previous study of Chenopodium album L. revealed that the light signal for anatomical differentiation of sun and shade leaves is sensed by mature leaves, not by developing leaves. They suggested that the two‐cell‐layered palisade tissue of the sun leaves would be formed without a change in the total palisade tissue cell number. To verify that suggestion, a detailed study was made of the developmental processes of the sun and shade leaves of C. album with respect to the division of palisade tissue cells (PCs) and the data was expressed against developmental time (leaf plastochron index, LPI). The total number of PCs per leaf did not differ between the sun and shade leaves throughout leaf development (from LPI ?1 to 10). In both sun and shade leaves, anticlinal cell division of PCs occurred most frequently from LPI ?1 to 2. In sun leaves, periclinal division of PCs occurred synchronously with anticlinal division. The constancy of the total number of PCs indicates that periclinal divisions occur at the expense of anticlinal divisions. These results support the above suggestion that two‐cell‐layered palisade tissue is formed by a change of cell division direction without a change in the total number of PCs. PCs would be able to recognize the polarity or axis that is perpendicular to the leaf plane and thereby change the direction of their cell divisions in response to the light signal from mature leaves.     

Developmental Morphology of Hop Stunt Viroid-infected Hop Plants and Analysis of Their Cone Yield1)

Infection of hop plants with hop stunt viroid (HSV) results in the retardation of the growth rate except for the rate of leaf emergence and the disappearance of the fold-like structure over the epidermal cell. Mature cones from HSV-infected hop plants remained small-sized and the content of α-acid was half to one third of that of HSV–free hop cones. In HSV-infected hop cones, the lupulin glands are distributed most abundantly on the bracteoles and the perianths and their numbers are reduced by at least 60% of that in the HSV-free control. Scanning electron micrographs confirm that most of the lupulin glands on bracteoles from HSV-infected hop cones shrivel severely, but not those from HSV-free hop cones. They also reveal that the lupulin glands on the perianths from both, HSV-free and HSV–infected hop cones become withered. Moreover, spherical granules (1.2 to 1.9μm in diameter) were not observed on the surface of the lupulin glands from HSV-infected hop cones.     

Genome‐wide transcript analysis of early maize leaf development reveals gene cohorts associated with the differentiation of C4 Kranz anatomy

Photosynthesis underpins the viability of most ecosystems, with C₄ plants that exhibit ‘Kranz’ anatomy being the most efficient primary producers. Kranz anatomy is characterized by closely spaced veins that are encircled by two morphologically distinct photosynthetic cell types. Although Kranz anatomy evolved multiple times, the underlying genetic mechanisms remain largely elusive, with only the maize scarecrow gene so far implicated in Kranz patterning. To provide a broader insight into the regulation of Kranz differentiation, we performed a genome‐wide comparative analysis of developmental trajectories in Kranz (foliar leaf blade) and non‐Kranz (husk leaf sheath) leaves of the C₄ plant maize. Using profile classification of gene expression in early leaf primordia, we identified cohorts of genes associated with procambium initiation and vascular patterning. In addition, we used supervised classification criteria inferred from anatomical and developmental analyses of five developmental stages to identify candidate regulators of cell‐type specification. Our analysis supports the suggestion that Kranz anatomy is patterned, at least in part, by a SCARECROW/SHORTROOT regulatory network, and suggests likely components of that network. Furthermore, the data imply a role for additional pathways in the development of Kranz leaves.