Color of plastic mulch affects lateral root development but not root system architecture in pepper

In 1999, 'Sweet Banana' pepper [Capsicum annuum L. (Grossum Group)] plants were grown under clean cultivation or with red, silver, or black polyethyle ne selective reflecting (SMR) mulches over the soil surface. Plants in each of three replications per treatment were Weld-set on 15 June. On 22 Sept., the plants were excavated and their root systems examined using a trench p rofile method and a succession of trench wall slices. The total numbers of roots of each plant at depths of 5, 10, 15, 20, and 25 cm and 10, 20, 30, 4 0, 50, and 60 cm from the plant stem were recorded, Distribution and archit ecture of the root systems were also examined, Plants grown under clean cul tivation developed 50 to 60 adventitious roots each, while those grown unde r red mulch developed approximate to 20 and those under black and silver mu lch about nine adventitious roots each. In all treatments, the adventitious roots radiated downward from the stem at an angle of 35 degrees from the h orizontal. No plants had vertical roots. Root system architecture was simil ar among treatments, with 40% of the roots in the upper 5 cm of soil and 70 % in the upper 10 cm, Thirty percent of the roots were within 10 cm, 50% wi thin 20 cm, and nearly 100% within 40 cm of the stem, Root numbers decrease d with increasing depth and distance from the stem. The greatest number of lateral roots were produced under silver mulch, intermediate numbers under clean cultivation and black mulch, and the fewest roots under red mulch. Co lored mulches influenced the total number of adventitious and lateral roots but not the root system architecture of pepper plants.