Abstract
A new technique was explored for classifying roots according to their ages, and it was applied for the analysis of root system development of the 1-to 7-year-old clonal tea plants (Camellia sinensis (L.) O. Kuntze cv. Yabukita) grown under field conditions. In the technique, the root ages were expressed progressively as Age I, Age II etc., by the number of annual rings, which were easily detected by staining cross sections of the roots with phloroglucinol-alcohol solution. Total root weight increased almost linearly with plant age. Annual increase of root dry weight amounted to about 110g per plant from the third to the seventh year after planting. The quantitative ratio of white roots, which are superior in nutrient absorption and biosynthesis of amino acids, maintained the highest ratio throughout every plant age examined. This suggests importance of white roots to plant growth and green tea quality. In contrast, Age III and IV roots occupied the smallest percentage among total roots. Roots that were formed within 3 years after planting continued to grow in the successive years. Most of those that were formed later in 4 or 5 years after, however, failed to grow in the successive years. Consequently, it is considered that growth of roots which were formed during the younger plant ages is of great importance for the formation of tea root system.
