Abstract

A study was conducted in kiwifruit vines (Actinidia deliciosa A. Chev.) in three different locations in central Chile to characterize the seasonal fine root growth in relation to shoot and fruit development as well as accumulated degree days (ADD). Growth of young roots, shoots, and fruits were studied at weekly intervals over an entire growing season. Root growth (young root lengths) was assessed using rhizotrons. White roots, shoots, and fruits growth curves were plotted against time over the studied period. Root growth was compared with shoots, fruit growth, and ADD during the same period and the relationship between ADD and shoots and fruits growth was evaluated. Elongation began in late November, after the beginning of shoots and fruits growth, and presented a bimodal growth pattern with the first peak between the end of spring and the beginning of summer and a second peak between the end of summer and the beginning of fall. The onset of shoot growth occurred on almost 70 days earlier than fruit and root growth with 46 to 62 ADD. Flowering occurred 56 to 58 days after bud burst (DABB) and at 210 to 231 ADD. Growth pattern reflected the competition within the vine for available assimilates, with the strongest sink being initially the developing shoots and subsequently the fruits. Logistic functions, which accounted for 89 to 93% of the variance in the three sites, were fitted to the response of shoot and fruit growth as a function of ADD.