A STUDY ON PLANT HEIGHT CONTROL OF IRIS FLOWERS

Abstract

We investigated the effect of paclobutrazol as preplant bulb soaks on plant height
of Iris x hollandica cv. ‘Frans Hals’ and ‘Blue Magic’cultivars which were grown
in pots. Bulbs of iris were soaked into gibberellin inhibitor paclobutrazol solution
at 0, 15, 30 ppm before planting. Effect of paclobutrazol on the flowering time,
flower diameter and length, leaf length, plant height, flower life, and chlorophyll
content of leaves were determined. The shortest plant height was obtained from the
‘Blue Magic’ cultivar treated with 30 ppm paclobutrazol which gave plants with
11.3 cm, 68% shorter than untreated control. ‘Frans Hals’ cultivar treated with 30
ppm paclobutrazol was 20.9 cm and 50% shorter than control. In ‘Blue Magic’ and
‘Frans Hals’cultivars the lower dose of 15 ppm paclobutrazol were also effective
on height control with 11.8 and 21.5 cm plant height, respectively. This gibberellin
inhibitor also shortened the leaf length of iris cultivars. Paclobutrazol treatments
resulted in higher chlorophyll content per unit area in the leaves. The highest
chlorophyll content (57.00 CCI) was obtained from the ‘Blue Magic’ iris treated
with 30 ppm paclobutrazol, while the control plants had 32.70 CCI chlorophyll in
their leaves. Chlorophyll content of ‘Frans Hals’ treated with 30 ppm paclobutrazol
were 52.87 CCI, while control plants of this cultivar were 28.80 CCI. Plants
applied with paclobutrazol resulted with smaller flower diameter compared to the
control plants of both cultivars. The smallest flower diameter was obtained from 30
ppm paclobutrazol treatment with 38.83 mm in ‘Blue Magic’ iris while the control
of this cultivar was 99.63 mm. The flower diameter of ‘Frans Hals’ cultivar treated
with 30 ppm paclobutrazol was 109.1 mm, while the control one was 112 mm.