seed piece seed piece

Source: Islam et al. (1978), aExpressed as percentage of total number of shoots, swollen buds, and visible but apparently dormant buds; *, **, *** denotes significant differences from control treatment at P = .05, P = .01, and P = .001, respectively.

substantial increase in shoot growth during the first 23 days of growth (Table 2.10). Ethrel was more effective in increasing the number of roots per rhizome piece by a factor of 4.0 and the number of shoots having roots by a factor of 3.7 (both at day 16). Relatively low concentrations of ethrel (less than 250 ppm) were sufficient to produce maximum responses in terms of shoot length parameters, although significant increases in the number of shoots per seed piece, the number of rooted shoots, and the total number and length of roots per seed piece occurred even up to the highest concentrations of 1,000 ppm studied by Islam et al. (1978). Treatment of ethrel was found to be effective in reducing the variability in root growth, but shoot growth variability had increased particularly at concentrations below 500 ppm.

Furutani and Nagao (1986) investigated the effect of daminozide, gibberellic acid (GA3), and ethephon on flowering, shoot growth, and yield of ginger. Field-grown ginger plants were treated with three weekly foliar sprays of GA3 (0, 1.44 and 2.88 mM); ethephon (0, 3.46, and 6.92 mM), or daminozide (0.3, 13, and 6.26 mM). GA3 inhibited flowering and shoot emergence, whereas ethepon and daminozide had no effect on flowering but promoted shoot emergence. Rhizome yields were increased with daminozide and decreased with GA3 and ethephon.

Ravindran et al. (1998) tested three growth regulators—triacontanol, paclobutrazole, and GA3—on ginger to find out their effect on rhizome growth and developmental anatomy. Paclobutrazole- and triacontanol-treated rhizomes resulted in thicker walled cortical cells compared to GA3 and control plants. The procambial activity was higher in plants treated with triacontanol and paclobutrazole. In the cambium layers, the fusiform cells were much larger in paclobutrazole-treated plants. Growth-regulator treatment did not affect the general anatomy, although dimensional variations existed. The numbers of vascular bundles were more in plants treated with paclobutrazole and triacontanol. Paclobutrazole-treated plants exhibited greater deposition of starch grains than other treatments. The fiber content in the rhizome was less in GA3-treated rhizome. A higher oil cell index and higher frequency oil cells were observed in paclobutrazole-treated rhizome (Table 2.11). GA treatment also led to considerable increase in the number of fibrous roots.

Growth-Related Compositional Changes

Baranowski (1986) studied the cv. Hawaii for 34 weeks and recorded the growth-related changes of the rhizome. The solid content of the rhizome increased throughout the season, but there was a decline in the acetone extractable oleoresin content of dried ginger. However, the oleoresin content on a fresh weight basis was roughly constant (Table 2.12).

The (6)-gingerol content of ginger generally increased with the age of the rhizome on a fresh weight basis (Table 2.13) These results indicate the basis for the gradual increase in pungency with maturity. On a dry weight basis, gingerol generally exhibited a linear increase with maturity up to 24 weeks, followed by a steady decline through the rest of the period. The results, in general, indicate that it may be advantageous to harvest ginger early (i.e., by 24 weeks) for converting to various products.

Table 2.11 Effect of triacontanol, paclobutrazol, and GA3 on rhizome characters of ginger

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