My thesis is that understanding stomatal patterning requires a holistic perspective. Since stomata are structures critical to the survival of terrestrial plants, they need to be viewed in relation to their function and their interface with other structural components. With this outlook, I begin by discussing pattern types, means of measuring them, advantages of each type of measurement, and then present patterning from evolutionary, physiological, ecological, and organ views. I suggest areas where I believe profitable studies might enable us to better understand stomatal patterning. The final sections of the paper review stomatal patterning on angiosperm leaves and present a theory of patterning. With the abundance of molecular information, and coming genomic sequences and new tools, an opportunity exists to dissect the process of how cells are selected to become different from their neighbors and assume a fate critical to plant survival. Understanding this biological process at the molecular level requires comprehending the broad base on which stomatal patterning rests.

ABSTRACrHydrogen-I nuclear magnetic resonance spectroscopy was used to study water allocation in cell compartments of sun and shade leaves.NMR spectra ofAcerpltanoides were resolved into two peaks that were assied to chloroplast and nonchloroplast water. Sun leaves contained 1.7 times more water per unit area of surface than shade leaves, and the water was allocated differently. Chloroplasts in sun leaves contained 17% of the total leaf water versus 47% in shade leaves. Comparing equal leaf surface areas, the chloroplasts in shade leaves contained 60% more water than those in sun leaves.

We examined spatial relations of arrested stomatal initials and their differentiated state on leaves of the monocotyledon Tradescantia. The placement and proximity of stomata and arrested stomatal initials to the five nearest stomata were studied to test the hypothesis that if developing stomatal initials occur too close to one another, initials will arrest. The results showed that arrested stomatal initials were not randomly placed, but were closely associated with another stoma, most often in an adjacent cell file. The distance to their nearest stomatal neighbors was less than the equivalent distance between stomata that mature. After stomatal initials form, their position within or across cell files was not adjusted by cell division or expansion. Synergistic effects from several neighboring stomata could not be linked to stomatal arrest; rather, arrest was associated only with the nearest stomatal neighbor. Since the arrest of stomatal initials was distance dependent, a failure intrinsic to the arrested initials is not solely responsible for halting stomatal development. These data show that an inhibitory mechanism adjusts stomatal development to influence the final distribution of Tradescantia stomata. The pigmentation and expansion characteristics of arrested stomatal initials were like those of epidermal cells, indicating that the initials did not remain halted at a specific point in their development. The capacity of arrested initials to differentiate in the epidermal cell pathway indicates that they remain pluripotent after their initial specification and that the opportunity for patterning is long enough to permit their entry into the epidermal cell pathway.

A study of floating and submerged Salvinia leaves using light and scanning electron microscopy shows unique features in the arrangement of leaves and their growth. Leaves are produced in phyllotactic units of six; within each phyllotactic unit are two sets or groups of three leaves each. The genetic spiral of leaf initiation is not unidirectional but alternates from clockwise to counterclockwise with the production of each group of three leaves. Within each group of leaves, the sequence of primordial expansion is the reverse of their inception. Observations of floating leaf apical cells show that during development they undergo configurational changes from rectangular to hemisperical to lenticular to tetrahedral. Floating and submerged leaves diverge structurally when they are 70–90μm in length. The general course of leaf development appears to differ from previously described ferns and angiosperms in that each floating leaf blade panel is generated from the abaxial primordial surface.

Pure culture isolates were obtained from fungi fruiting in the vicinity of dwarf willows at Barrow and Cape Simpson, Alaska. Four of these isolates and one isolate from Maryland were tested for their ability to form ectomycorrhizae with cuttings of Salix rotundifolia under controlled environmental conditions. Isolates of Entoloma sericeum, Hebelomapusillum, and Cenococcum geophilum from Barrow and Cape Simpson, Alaska all formed typical ectomycorrhizae with S. rotundifolia, while an isolate of C. geophilum from a temperate ecosystem (Maryland) did not.All of the ectomycorrhizae synthesized with S. rotundifolia, plus uncolonized roots, demonstrated an ability to hydrolyze p-nitrophenyl phosphate at a pH of 4.7. The acid phosphatase activity of E. sericeum ectomycorrhizae was from 10 to 40 times as great as that demonstrated by other mycorrhizal and nonmycorrhizal roots on a surface area basis.