The objective of this study was to determine the differences between maize (Zea mays L ) and sunflower (Helianthus annuus L.) in the pattern of leaf chlorophyll content and spectral properties occurring with leaf ageing and senescence. Chlorophyll accumulation and leaf spectral properties were determined in growing and senescing leaves of field-grown maize and sunflower hybrids. Measurements were taken at intervals of 3-4 days during the rapid stem elongation phase on leaf II for maize and leaf 17 for sunflower. Reflectance (R) and transmittance (T) spectra of adaxial surfaces of attached leaves were measured using a LI-COR 1800 hand-held spectroradiometer with an external integrating sphere, over the wavelength range from 400 to 1 100 nm. Absorptance (A) was computed as: A= 100- (R +T). In the growing leaf, chlorophyll content increased until full leaf expansion, while no changes in A and T were recorded. After full leaf expansion was reached, chlorophyll dropped from 514.3 to 328.0 µmol m-2 in maize and from 527.2 to 164.1 µmol m-2 in sunflower. Absorptance in the PAR region declined about 5% in maize and about 11% in sunflower and T increased about 1% in maize and 7% in sunflower. Within the PAR region, variations in A and T were recorded only in the green band (520-600 nm) for maize and in the green and red (630-690 nm) bands for sunflower. There were differences between maize and sunflower in the relative timing of the decrease in chlorophyll content and A in senescing leaves: maize retained chlorophyll longer than sunflower and A declined more slowly in maize as a result of the different length of leaf maturity and senescing stages.
CHANGES IN SPECTRAL PROPERTIES OF AGING AND SENESCING MAIZE AND SUNFLOWER LEAVES
MASONI, ALESSANDRO;MARIOTTI, MARCO;
1994-01-01
Abstract
The objective of this study was to determine the differences between maize (Zea mays L ) and sunflower (Helianthus annuus L.) in the pattern of leaf chlorophyll content and spectral properties occurring with leaf ageing and senescence. Chlorophyll accumulation and leaf spectral properties were determined in growing and senescing leaves of field-grown maize and sunflower hybrids. Measurements were taken at intervals of 3-4 days during the rapid stem elongation phase on leaf II for maize and leaf 17 for sunflower. Reflectance (R) and transmittance (T) spectra of adaxial surfaces of attached leaves were measured using a LI-COR 1800 hand-held spectroradiometer with an external integrating sphere, over the wavelength range from 400 to 1 100 nm. Absorptance (A) was computed as: A= 100- (R +T). In the growing leaf, chlorophyll content increased until full leaf expansion, while no changes in A and T were recorded. After full leaf expansion was reached, chlorophyll dropped from 514.3 to 328.0 µmol m-2 in maize and from 527.2 to 164.1 µmol m-2 in sunflower. Absorptance in the PAR region declined about 5% in maize and about 11% in sunflower and T increased about 1% in maize and 7% in sunflower. Within the PAR region, variations in A and T were recorded only in the green band (520-600 nm) for maize and in the green and red (630-690 nm) bands for sunflower. There were differences between maize and sunflower in the relative timing of the decrease in chlorophyll content and A in senescing leaves: maize retained chlorophyll longer than sunflower and A declined more slowly in maize as a result of the different length of leaf maturity and senescing stages.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
