Elevational patterns of endogenous hormones and their relation to resprouting ability of Quercus aquifolioides plants on the eastern edge of the Tibetan Plateau

Key message

Above- and belowground tissues showed different trends in IAA, CTK and CTK/IAA ratios with elevations, and coppicing changed the levels of endogenous hormones that are related to resprouting ability.

Abstract

Little is known about how plant hormones and nitrate concentrations change in plants with increasing elevations, and whether the alpine treeline formation and the decreased resprouting ability of plants at high elevations are correlated with such changes. We studied tissue hormones and nitrate concentrations in Quercus aquifolioides plants before and after coppicing at 3,000, 3,500 m, and their uppermost distribution of 3,950 m a.s.l. in southwestern China. Concentrations of indole-3-acetic acid (IAA) significantly increased, but concentrations of cytokinins (CTK) and CTK/IAA ratios decreased in aboveground tissues of intact plants with increasing elevations. The altitude had reverse effects on these parameters in belowground tissue. Coppicing changed the levels of IAA, CTK, and nitrate concentrations, as well as the CTK/IAA ratios, but not their elevational patterns in either stumps or roots. These results imply that the elevational patterns of plant hormones reflect mainly the effects of altitude associated with gradual changes in temperature and radiation condition on hormones along an elevational gradient. Both CTK concentrations and CTK/IAA ratios in stumps were significantly positively correlated with resprouting ability, but in fine roots they were negatively correlated. This indicates that CTK, which is synthesized in the root cap, needs to move from the roots into the stumps to initiate the growth of lateral buds. Our results suggest that for coppice regeneration management practices to be successful, the root system needs to be carefully protected from damage.