Seasonal changes in anatomical and morphological structure and the content of phytohormones and sugars in underground shoots of a long-rhizome perennial grass Phalaroides arundinacea

Abstract

Seasonal changes in the anatomical and morphological structure and metabolic activity of rhizomes were studied in a perennial grass reed canary-grass (Phalaroides arundinacea (L.) Rauschert). An active formation of the underground stock of meristems and a rhizome weight accumulation were shown in the later half of a growth period, after a decline in the growth of aboveground shoots. A reduction in the cross-section area and the relative contribution of the central cylinder together with of an increase in the volume of a cortex parenchyma were found in the rhizomes at the end of the growth period. In autumn, the rhizomes were characterized by the high content of cytokinins and oligosaccharides; which reserves determines the resistance of underground shoots to low temperatures and prevents the frost damage to underground meristems, whereas the levels of other phytohormones (IAA, ABA, and GA) significantly decreased at this period. In the autumn, the optimum temperatures for the rhizome growth shifted to low above-zero temperatures, reflecting the adaptation of morphogenetic processes related to the bud formation. The authors conclude that the temperature depression rather than the accumulation of growth inhibitors is the basic factor determining rhizome exogenous dormancy.