Abstract: Mountain altitudinal gradient contains the changes of multiple environmental parameters, and fine roots, functioning as the basis of plants in absorbing water and nutrient, are sensitive to these environmental changes. In this study we investigated the response of fine root morphology to the altitudinal gradient in the Panquangou National Nature Reserve in Shanxi Province, northern China, to improve our understanding of the underground processes of plants in the context of global environmental change. We measured the variations of root morphology, including diameter, root tissue density, specific root length and specific root surface area, among different root orders for Larix principisrupprechtii (distributed in 1800-2700 m above sea level). The data showed that (1) For the same root order, with the elevation increasing, root diameter increased and root tissue density (RTD) decreased, while specific root length (SRL) and specific root surface area (SRA) showed low values at the low and high elevations; (2) At each altitude, root diameter and RTD increased along with the root order increasing, but SRL and SRA declined; (3) The analysis of variance showed that  altitude and root order  significantly influenced  the morphology of fine roots   (P < 0.05), and they interacted to exert influence on the root diameter and RTD only (P<0.05). For the first three root orders, root diameter and RTD were closely related with the altitude (P < 0.05). However, for the fourth and fifth root orders, the correlation between altitude and the four morphology characteristics was not significant. These results are important for understanding the mechanism of response of fine roots to future climate change.

Key words: tomato, heat stress, photosynthesis, manntiol-calcium, nano-calcium, CaCl₂.