Influence of the testa on seed dormancy, germination, and longevity in Arabidopsis

The testa of higher plant seeds protects the embryo against adverse environ mental conditions. Its role is assumed mainly by controlling germination th rough dormancy imposition and by limiting the detrimental activity of physi cal and biological agents during seed storage. To analyze the function of t he testa in the model plant Arabidopsis, we compared mutants affected in te sta pigmentation and/or structure for dormancy, germination, and storabilit y. The seeds of most mutants exhibited reduced dormancy. Moreover, unlike w ild-type testas, mutant testas were permeable to tetrazolium salts. These a ltered dormancy and tetrazolium uptake properties were related to defects i n the pigmentation of the endothelium and its neighboring crushed parenchym atic layers, as determined by vanillin staining and microscopic observation s. Structural aberrations such as missing layers or a modified epidermal la yer in specific mutants also affected dormancy levels and permeability to t etrazolium. Both structural and pigmentation mutants deteriorated faster th an the wild types during natural aging at room temperature, with structural mutants being the most strongly affected.