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Physiological Section

Olowoyeye, Kehinde [2], Osborne, Bruce [1], Keane, George [2].

Photosynthesis and biomass production of Zea mays sown under plastic..

The establishment of potentially important crops such as maize under temperate condition is often limited by low temperature. Experiments have shown that the use of photodegradable plastic coverings has resulted in an increased performance of maize under temperate conditions. This study examines photosynthetic and fluorescence responses of three maize varieties, Justina and Hudson, regarded as chilling-tolerant and Ethiopian a chilling-sensitive variety subjected to two treatments of complete plastic and no plastic covering. Experiment was set up in growth cabinet at constant 10 C and 70% relative humidity with 18/6hrs photoperiod and PAR of 450-650m mol m-2 s-1 of which 85-90% penetrates the plastic. There was 1-3 C and 13-23% increase in temperature and relative humidity below the plastic. Photosynthetic responses to light measured between 0-1400m mol m-2 s-1 of all varieties from both treatments was determined from gas exchange measurements 6 weeks after planting along with chlorophyll fluorescence, shoot height and leaf area. There was no light saturation and no net photosynthesis in seedlings from both treatments except in Hudson under the plastic, with an insignificant rate of photosynthesis. Efficiency of PS11 was slightly higher in plants under the plastic relative to those without the plastic covering. To simulate the period maize plants pushes through the photodegradable plastic on the field plastics were perforated at 6 weeks exposing plants to the lower temperature and higher light intensity in the cabinet. Measurements on gas exchange and fluorescence showed depressions in PS11 efficiency and CO2 assimilation of all three varieties from both treatments. Rates of shoot elongation and leaf expansion were higher in varieties under the plastic than varieties without the plastic covering. Continuous exposure of seedlings under the plastic to the 10oC temperature along with those without the plastic led to yellowing of the leaves and eventual withering of the plants.

1 - University College Dublin, Department of Botany, Belfield, Dublin, 4, Ireland
2 - University College Dublin, Department of Crop Science, Belfield, Dublin, 4, Ireland

low temperature
photodegradable plastic.

Presentation Type: Poster
Session: 32-63
Location: Special Event Center (Cliff Lodge)
Date: Tuesday, August 3rd, 2004
Time: 12:30 PM
Abstract ID:207

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