Molecular Effects of Hormone Treatment on Tissue

Transgenic Tobacco Plants Coexpressing the Agrobacterium tumefaciens iaaM and iaaH Genes Display Altered Growth and Indoleacetic Acid Metabolism

“…Such responses are well known from exogenous auxin application studies (2) Internodes Leaves possible that increased lignification restricted cell growth, as was suggested for tomato plants treated with IAA (18). Another possibility is that the high IAA levels inhibited stomatal opening by decreasing root permeability (33). This is supported by our observation that line C plants, compared to wild type, had a decreased stomatal conductance and, thus, a decreased CO2 assimilation rate (unpublished data).…”

Growth Regulators Have Rapid Effects on Photosynthate Unloading from Seed Coats of Phaseolus vulgaris L.

“…However, the effects ofboth growth regulators are suggestive of direct action on membrane permeability. Certainly, for ABA it is well documented that it closes stomata within minutes (27) and it is now generally accepted that many growth regulators including cytokinins and ABA can change the properties of cell membranes without the need for changes in enzyme synthesis (28).…”

Root Contraction in Hyacinth. I. Effects of IAA on Differential Cell Expansion

“…An additional and unaddressed aspect ofroot contraction is the understanding of differences between inner (active) and outer cortical cells, particularly with regard to their respective abilities to undergo growth reorientation. It is well established that auxins, and perhaps other plant hormones, can cause changes in the mechanical properties of cell walls (Vanderhoef, 1980;Wareing and Phillips, 1981;Zeroni and Hall, 1980). Furthermore, auxin-induced promotion of elongation/expansion growth is positively correlated with changes in cell wall extensibility in many systems (Wareing and Phillips, 1981), and auxin-induced ethylene production results in lateral expansion of stem and root tissues (Abeles, 1973;Eisinger, 1983).…”

“…This differential growth and activity in intact roots could be based on a number of factors, including capacities of particular cells to resume or continue growth, ability of cells to reorient cell expansion, and/or sensitivity of specific cells to growth promoting substances. In an attempt to gain a better understanding of the nature and role of differential cell expansion in root contraction, developing contractile roots were subjected to treatments with indole-3-acetic acid (IAA), a hormone known to play an important role in cell enlargement phenomena in a variety of tissues and organs (Carlton, 1943;Vanderhoef, 1980;Wareing and Phillips, 1981;Zeroni and Hall, 1980). The objectives ofthe present study were, therefore, two-fold: 1) to examine the effect of exogenously applied IAA on subsequent hyacinth root contraction; and 2) to compare certain characteristics of inner (active) and outer cortical cells in contracted and uncontracted roots and in tissues which developed in the presence of IAA.…”