Ageratum

Abstract: BOTANY Ageratum is derived from the Greek “a geras,” meaning non-aging, referring to the longevity of the flowers or the whole plant. The specific epithet “conyzoides” is derived from “konyz,” the Greek name of Inula helenium, which it resembles (Kissmann and Groth 1993). The synonyms of A. conyzoides include A. album Stend; A. caeruleum Hort. ex. Poir.; A. coeruleum Desf.; A. cordifolium Roxb.; A. hirsutum Lam.; A. humile Salisb.; A. latifolium Car.; A. maritimum H.B.K.; A. mexicanum Sims.; A. obtusifolium Lam.; A. odoratum Vilm. and Cacalia mentrasto Vell. (Jaccoud 1961). In Brazil, A. conyzoides has the following vernacular names: catinga de bode, catinga de barrao, erva de sao joao, maria preta, mentrasto, erva de sao jose, picao roxo, erva de santa-lucia, camara-opela, agerato, camara apeba, camara iapo, camara jape, erva de santa maria, macela de sao joao, macela francesa, matruco (Jaccoud 1961; Oliveira et al. 1993). Ageratum ranges from Southeastern North America to Central America, but the center of origin is in Central America and the Caribbean. Most taxa are found in Mexico, Central America, the Caribbean, and Florida. Ageratum conyzoides now is found in several countries in tropical and sub-tropical regions, including Brazil ( Baker 1965; Lorenzi 1982; Correa 1984; Cruz 1985). Johnson (1971), classifies two subspecies, latifolium and conyzoides. Subspecies latifolium is found in all the Americas and subsp. conyzoides has a pantropical distribution. The basic chromosome number is 2n = 20 but natural tetraploids are found. A. conyzoides subsp. latifolium is diploid and A. conyzoides subsp. conyzoides is tetraploid. Ageratum conyzoides is an erect, herbaceous annual, 30 to 80 cm tall; stems are covered with fine white hairs, leaves are opposite, pubescent with long petioles and include glandular trichomes. The inflorescence contain 30 to 50 pink flowers arranged as a corymb and are self-incompatible (Jhansi and Ramanujam 1987; Kaul and Neelangini 1989; Ramanujam and Kalpana 1992; Kleinschimidt 1993). The fruit is an achene with an aristate pappus and is easily dispersed by wind. In some countries the species is considered a weed, and control is often difficult (Lorenzi 1982; Scheffer 1990; Kalia and Singh 1993; Lam et al. 1993, Paradkar et al. 1993; Waterhouse 1993; Kshatriya et al. 1994). Seeds are positively photoblastic, and viability is often lost within 12 months (Marlks and Nwachuku 1986; Ladeira et al. 1987). The optimum germination temperature ranges from 20 to 25°C (Sauerborn and Koch 1988). The species has great morphological variation, and appears highly adaptable to different ecological conditions.

Abstract: Daily light integral (DLI) describes the rate at which photosynthetically active radiation is delivered over a 24-hour period and is a useful measurement for describing the greenhouse light environment. A study was conducted to quantify the growth and flowering responses of bedding plants to DLI. Eight bedding plant species [ageratum (Ageratum houstonianum L.), begonia (Begonia ×semperflorens-cultorum L.), impatiens (Impatiens wallerana L.), marigold (Tagetes erecta L.), petunia (Petunia ×hybrida Juss.), salvia (Salvia coccinea L.), vinca (Catharanthus roseus L.), and zinnia (Zinnia elegans L.)] were grown outdoors in direct solar radiation or under one of three shade cloths (50, 70 or 90% photosynthetic photon flux (PPF) reduction) that provided DLI treatments ranging from 5 to 43 mol.m -2 .d -1 . The total plant dry mass increased for all species, except begonia and impatiens, as DLI increased from 5 to 43 mol.m -2 .d -1 . Total plant dry mass of begonia and impatiens increased as DLI increased from 5 to 19 mol.m -2 .d -1 . Impatiens, begonia, salvia, ageratum, petunia, vinca, zinnia, and marigold achieved 50% of their maximum flower dry mass at 7, 8, 12, 14, 19, 20, 22, and 23 mol.m -2 .d -1 , respectively. The highest flower number for petunia, salvia, vinca, and zinnia occurred at 43 mol.m -2 .d -1 . Time to flower decreased for all species, except begonia and impatiens, as DLI increased to 19 or 43 mol.m -2 .d -1 . There was no consistent plant height response to DLI across species, although the shoot and flower dry mass per unit height increased for all species as DLI increased from 5 to 43 mol.m -2 .d -1 . Guidelines for managing DLI for bedding plant production in greenhouses are discussed.