Info

10.8b

146.7b

13.58a

40.2a

Values followed by the same letters are not significantly different. 'Natural day length decreased from 13.46 h (June 29) to 10.41 h (Nov. 29) yMean separation with in cultivars by Duncan's multiple range test, 5% level.

Values followed by the same letters are not significantly different. 'Natural day length decreased from 13.46 h (June 29) to 10.41 h (Nov. 29) yMean separation with in cultivars by Duncan's multiple range test, 5% level.

the 15 th day and then declined gradually (Table 2.8). In the first 40 days of leaf growth, the malondialdehyde (MDA) content of leaves remained constant and SOD (superoxide dismutase) activity showed a little decrease. After 40 days, the MDA content increased markedly and SOD activity dropped substantially. Peroxidase (POD) and catalase activities exhibited a steady increase during 60 days. Xizhen et al. (1998) concluded that senescence of ginger leaf sets in when leaf age reaches about 40 days.

Xizhen et al. (1998) also studied the photosynthetic characteristic of different leaf positions, and reported that the Pn of midposition leaves was the highest followed by the lower leaves and Pn was lowest in upper leaves. The light compensation point of different leaf positions was from 18.46 to 30.82 |xmol/m2s_1; it was highest in midpo-sition leaves and lowest in lower leaves. The light saturation point ranged from 624.8 to 827.6 ^mol/m2s_1, the values were 624.8, 827.6 and 799. 5 ^mol/m2s_1, respectively, in upper, middle, and lower leaves. CO2 compensation points in upper, middle, and lower position leaves were 163.8, 29.6 and 71.4 |l/l, respectively. CO2 saturation in upper, middle, and lower leaves were 1543.3, 1499.0 and 1582.0 ^l/l. The diurnal variation of Pn in different leaf positions gave a double peak curve, the first peak was at about 9:00 a.m. and the second appeared from 1300 to 1400 hours.

Stomatal Behavior and Chlorophyll Fluorescence

Dongyun et al. (1998) studied the chlorophyll fluorescence and stomatal behavior of ginger leaves. Ginger leaves were enclosed individually in cuvettes and studied to find

Table 2.8 Changes of chlorophyll content and photosynthetic rate during development of ginger leaves

Leaf age (days)

Chlorophyll content(mg ■ g ')

Pn (^mol m 2 ■ s ')

1 day

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