Optical & physical properties of flowers & stems: UV to IR & surface texture adaptations for little-known thermal relations in plant growth and reproduction

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Biophysical and optical properties contribute to functionality of flowers and herbaceous stems in pollination, pollinator attraction, interior microclimate for development, growth, maturation and sexual reproduction. The proposed interdisciplinary research, embraces functional plant morphology at organismic, tissue and cellular levels. That, coupled with micrometeorology, optical biophysics from UV to IR, and thermometry through standard instrumentation, constitutes a new, interdisciplinary approach in botany with ramifications in co-evolutionary ecology. Floral features embody plant-pollinator co-adaptations. Macro- and microscopic features work via sensory (visual, chemical and tactile) perception by pollinators. Colours are often coupled to scent and epidermal microtextural features. Together they provide mirror-like (specular) to matte (diffused) reflections and perhaps iridescence and fluorescence. Pigments in epidermal or mesophyllic tissues, in organelles (plastids) or in protoplasmic solution, variously influence effectiveness in coloration (Kubelk-Munk models). Further, many flowers warm by insolation that aids growth and maturation and, as used by flower-basking pollinators. Best known are diaheliotropic (sun-tracking) bowl-shaped flowers as reflective solar furnaces. Less understood are microthermic regimes in enclosed and pubescent blossoms. Presumably insolation penetrates translucent structures, heats interior structures which re-radiate IR that becomes trapped, a microgreenhouse. Thermal/optical biophysics of hollow herbaceous stems acting as microgreenhouses constitutes similarly novel research. Preliminary data (2017) indicate that hollowness is common (2/3 of ca. 120 herb species sampled) and such stems (5 species tested) become heated by 5-6 C above ambient. The proposed research on the thermal/optical biophysics of flowers and stems will examine, through observation and experimentation, the incidence and extent of microthermic environments (measured by small temperature sensors and IR thermal imaging) within plant structures and their influences on growth, maturation and reproductive output under natural and controlled conditions. Biophysical mechanisms will be examined in selected plants through microscopy and histology combined with (UV-visible-near IR reflectance/absorbance spectrophotometry (to include transparency, translucence, fluorescence etc.), emissivity, thermal conductivity. Quantification of those characteristics in different plants and plant structures will allow for comparative assessments of colorimetric, structural, anatomical, and thermal properties of plant tissues associated with the adaptive significance of plants' differential, and presumably varying, usages of natural radiant energy in various habitats and at different times of day and year.