Abstract
The partitioning of net total dry matter (NTDM) production to roots of two clones, TRI 2023 and TRI 2025 were studied at four different altitudes, 30 m, 914 m, 1300 m, and 1859 m (above mean sea level) in Sri Lanka. At all altitudes, clone TRI 2023 partitioned more NTDM to its roots than clone TRI 2025 thus resulting in a larger increment of root dry matter at the end of the experimental period. The fall in mean air temperature (Tmean) effected by altitude caused a linear increase in the partitioning of NTDM to roots in both clones (R2 = 0.96, 0.85). However, clonal differences (P < 0.001) increased as altitude rose, due to the greater thermal sensitivity of the partitioning of NTDM to roots in clone TRI 2023 (2.7% oC-1) over TRI 2025 (0.97% oC-1). Results suggest that the environmental factors which are associated with the site rather than altitude may influence the root weight ratio of a tea bush. The thermal response of the partitioning of dry matter to roots is discussed in relation to pruning, yield, and longevity of the productive life of a tea bush.
