Fine Structural Analysis of the Elongation Zone of Easter Lily (Lilium longiflorum) Staminal Filaments

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Abstract
To seek fine structural correlates with the rate of plant cell elongation, we studied staminal filaments of Easter lily (Lilium longiflorum L.). These represent a population of homogeneous, rapidly elongating cells; their length increased at a constant rate directly proportional to bud length. Elongation proceeded from the tip to the base; the most rapid elongation was recorded for basal cells of excised filaments. When the growth rate of excised filaments varied as a function of temperature, no differences were observed in relative abundance or orientation of organelles. Numbers of cytoplasmic vesicles or vesicles associated with dictyosomes remained constant. Similar results were obtained with auxin-treated filaments, although filaments treated with growth-inhibiting concentrations of calcium chloride appeared to have fewer dictyosome-associated vesicles. The only consistent correlation was an inverse relationship between growth rate and luminal diameter of the endoplasmic reticulum (ER). In addition, at the lowest temperatures (0-4 C), the incidence of connections between ER and other structures, including vacuoles and dictyosomes, appeared to increase.