Growth And Flowering Of Clerodendrum Thomsonae Balf

Abstract

These investigations were conducted to determine the effect of growth regulators and environmental factors on the growth and flowering of Clerodendrum thomsonae Balf. "Wisconsin" clone. Whether terminal or stem-bud cuttings were used, there was little difference in growthand flowering of the plants. plants propagated from cuttings taken from the uppermost portion of the stem of young stock plants (four months) developed about five times as many flowers as t.hose from old stock plants (one and one-half years). plants defoliated and water stressed for one week produced axillary shoots at 79% of the nodes compared to axillary shoots at 5.3% of the nodes of non-defoliatE:d and non-water stressed plants. Of eight different media used, a peat-vermiculite-sand medium was most satisfactory for growth-a-nd flowering. plants grown in a medium at pH (6.9) and treated with ancymidol (30 ppm used as a drench at the rate of 30 ml/four inch pot) produced more -flowers than plants grown in media with a pH of 5.0 or lower. Ancymidol treated piants had twice the concentration of N, P, and K present in untreated plants. plants receiving as low as 80 ppm N and as high as 320 ppm N showed little difference in growth and flower development.' The dry wt of leaves, stems, and roots decreased with increased ancymidol concentrations. plants grown from stem-tips given heat therapy were virus free and produced the same number of flowers as plants that did not receive heat therapy. Elongation of untreated plants was considerably greater than ancymidol treated onp.s regardless of photoperiod; whereas, there was little effect of light intensity on the elongation of treated and untreated plants. Ancymidol treated plants produced as much as a 50-fold increase in flowers compared to untreated ones. In controlled environment chambers, fewer flowers were produced under low light intensity (under 1200 ft-c) than under high light intensity (6500 ft-c). plants exposed to ~ hour of red light before the dark period in both sl)ort and long days flowered profusely; whereas, those exposed to Ear-red remained vegetative. Of the numerous growth regulators tested, encapsulated cycocel and ancymidol stimulated flowering and inhibited excessive elongation. Studies on the former were discontinued because of severe chlorosis and leaf distortion. Morphactin stimulated axi.llary shoot development, but also caused extensive apical and foliar injury. Ancymidol retarded growth of plants whereas gibberellic acid (Gl'l.3) only and GF_3 plus ancyrnido L promoted stem elongation. Untreated and ancymidol treated plants grown under a IS-hour photoperiod remained' vegetative, but flowered under a 12-hour photo period , Plants treated with GA3 and GA3 plus ancymidol remained vegetative in both 12 and 15-hour photoperiods. Anatomical examinations of the stem tips revealed that ancymidol enhanced the early development of floral parts however, untreated plants flowered at nearly the same time as treated ones. 'The reason for this may 'be that the greater number of flowers produced on ancymidol treated plants require a greater amount of photosynthate. There was a striking increase in gibberellic acid in flowering compared to vegetative plants. The Effeciveness of ancymidol to increase the GA concentration which may induce plants to flower strengthens the hypothesis that ancymidolI does not interfere with inhibition of GA3 biosynthesis