Effect of temperature on growth of roots of juvenile asparagus (Asparagus officinalis L.) plants

It is difficult to observe the growth of root system and to measure its morpho-physiological parameters when asparagus is grown in the open field. Therefore, different from that cultivation method, juvenile asparagus plants were cultivated in aeroponics in greenhouse in this study. Under such conditions, investigation on the growth of roots became easier since it allowed nondestructive observation and examination of root system of asparagus. Seven asparagus cultivars from countries differing in climatic conditions were used in the study. When stems of juvenile plants were fully developed, their storage roots were taken for root respiration rate (R(r)) measurement at three temperatures: 10, 20 and 30°C. Regressions between R(r) and temperatures were analyzed for each cultivar. From these results, soil temperature was estimated based on the standard root respiration rate (R(rs)) observed from the experiment. Significant difference was found on R(r) of juvenile plants among cultivars at three temperatures. Reaction of roots to temperature changes also varied at different degrees among cultivars. Some cultivars were shown to be more suitable for growing at higher soil temperatures, indicating that the others should be cultivated in much lower soil temperature if R(r) needed to be equal to R(rs).