Tassel flower

Since the use of techniques to measure IAA, bioassays have been important to discover PGR activity of many other compounds. Several bioassays for the PGR gibberellic acid (GA3) have been developed. One bioassay was based on reduction of amaranthin levels in Amaranthus caudatus (tassel flower) seedlings.63 This method was sensitive to GA3 from 0.01 to 1 mg L"1. GA3 was also bioassayed, based on anthocyanin reduction in tomato (Lycopersicon esculentum L.).62 Reduction of anthocyanin in tomato seedlings was linear from 10"5 to 10 mg L 1, and thus, this latter plant bioassay method was more sensitive. A multitude of bioassays for nonvolatile and volatile plant growth regulator compounds have been developed and their uses and limitations have been discussed.129 Since many allelochemicals have been shown to have relatively weak phytotoxicity (especially compared to herbicides), some of these bioassays that have been developed for detecting and quantitatively measuring PGR activity may be useful in allelopathy. 

These standards can be met by adding male sterility traits to control pollen flow to avoid outcrossing. Some plant species that have enclosed flower structures would represent good candidates. A crop like corn, which is a wind-pollinated crop, can have tassels removed manually, and sterile varieties can be made to contain the pollen (Shama and Peterson, 2004). 

Maleic hydrazide was the first potentially useful commercial chemical for preventing the flowering of sugarcane but, at best, it gave only about 60% control. Rapid developments in the 1950 s led to the use of 3-(p-dichlorophenyl)-l,l-dimethylurea (monuron) as the chemical of choice and later to the use also of 3-(3,4-dichlorophenyl)-l,1-dimethylurea (diuron). When properly applied, 4 lb per acre of either chemical provides virtually complete control of flowering in the heavy-tasseling cane varieites used in the 1950 s and early 1960 s in Hawaii,... 

Maize is a tall annual grass plant with a strong, solid stem canying large narrow leaves. The male flowers are produced on a tassel at the top of the plant, and the female some distance away on one or more spikes in the axils of the leaves. This separation simplifles the production of hybrid seed. After wind pollination of the filament-like styles (silks), the grain develops in rows on the female spike (cob) to produce the maize ear in its surrounding husk leaves. 

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