A novelanomalous spiral secondary growth in roots of trianthema portulacastrum L

Abstract

The subclass Caryophyllidae of Cronquist (Centrospermae of Engler) is characterized by abnormal secondary thickening like concentric circles of alternating xylem and phloem in stems which is believed to be the pattern in roots also. But in the roots of Trianthema portulacastrum L. (Aizoaceae), three types of anomalies are seen in secondary thickening. The rst type, which is predominant, is a new “spiral” pattern in which secondary cambium arises from the conjunctive tissue near one of the primary phloem groups and it proceeds producing spirals of xylem inside and phloem outside and both the tissues end abruptly in cortex. In the second case, the secondary vascular tissues originate from the vicinity of both the primary phloem groups. In the third, both the primary phloem groups remain included in the encircling secondary xylem elements and secondary vascular tissues are formed in concentric rings of xylem and phloem.