The relation of root systems to shoot systems in vascular plants

The roots and shoots of vascular plants may be positionally and developmentally related in various ways. However, botanical teaching and research are strongly influenced by the paradigmatic annual dicotyledon, whose bipolar embryo develops into a plant with root and shoot meeting only at the hypocotyl. In 1930 Goebel criticized this example as a general model for plants, proposing instead the opposed concepts “allorhizy” (referring to plants whose root and shoot are related as above) and “homorhizy”(referring to plants without a bipolar embryo, all of whose roots are shoot-borne, e.g., pteridophytes). Goebel’s approach permeates the extensive German morphological literature, but has been virtually ignored in English-language literature. The allorhizy/homorhizy dichotomy has proved heuristic. However, it suggests a correlation between embryo type and mature morphology that does not always hold. Furthermore, it does not take into account the root-borne shoots typical of many plant species. Finally, Goebel’s presentation of the terms (which he does not explicitly define) creates ambiguity as to whether they designate structural concepts or the attributes of evolutionary groups. The alternative proposed here is a structural analysis of the possible topological relationships among root and shoot systems. Each structural class is then considered with regard to embryo types, potential for clonal growth and other ecological correlates, and phylogenetic distribution. This approach provides both a test of Goebel’s concepts and a basis for further comparative study of wholeplant form.     

Carbonic anhydrase in relation to higher plants

The review incorporates recent information on carbonic anhydrase (CA, EC: 4.2.1.1) pertaining to types, homology, regulation, purification, in vitro stability, and biological functions with special reference to higher plants. CA, a ubiquitous enzyme in prokaryotes and higher organisms represented by four distinct families, is involved in diverse biological processes, including pH regulation, CO₂ transfer, ion exchange, respiration, and photosynthetic CO₂ fixation. CA from higher plants traces its origin with prokaryotes and exhibits compartmentalization among their organs, tissues, and cellular organelles commensurate with specific functions. In leaves, CA represents 1–20 % of total soluble protein and abundance next only to ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPCO) in chloroplast, facilitating CO₂ supply to phosphoenol pyruvate carboxylase in C₄ and CAM plants and RuBPCO in C₃ plants. It confers special significance to CA as an efficient biochemical marker for carbon sequestration and environmental amelioration in the current global warming scenario linked with elevated CO₂ concentrations.     

The occurrence of estrogens in relation to reproductive processes in flowering plants

Summary Estrogens, a group of steroidal sex hormones, were determined in pollen, styles or whole pistils using a highly sensitive and specific radioimmunoassay (RIA) and found to be present at levels between 10^–11 and 10^–10 g/g FW. In the style of Liliun davidii Duch., the levels of total estrogen decreased after self-pollination of the open flower. After bud pollination, which partly overcame incompatibility, the levels of both estradiol and total estrogen increased. The levels of estradiol and total estrogen in the pistils of Brassica pekinensis Rupr. increased after compatible pollination during the first 3 days following pollination and decreased thereafter when the data were expressed on a FW basis. These results suggest that estrogens are to some extent associated with the reproductive processes.     

The effect of root temperature on rose plants in relation to air temperature

Rose plants (Rosa hybrida ‘Sonia’=‘Sweet Promise’) were grown in heated (minimum night temperature 17°C), and unheated greenhouses with or without root heating to 21°C. These trials covered 6 growth cycles extending over two winter seasons. In the heated greenhouse, root heating did not increase yield, flower quality or plant development. In the unheated greenhouse, root-heated plants grew as well as those in the air-heated greenhouse as long as the air temperature did not fall below 6°C. When minimum night temperatures fell below 6°C, growth, yield and quality were reduced, irrespective of root temperature. Daytime plant water relations were studied in plants growing at 6 different root temperatures in the unheated greenhouse. Leaf resistance to water diffusion was lowest at optimal root temperature. Total leaf water potential was not significantly affected by root temperature.