Growth, biomass allocation and water use efficiency of two wheat cultivars in a mediterranean environment; a pot experiment under field conditions

Abstract

Plants of two bread wheat cultivars, Triticum aestivum L. 'Katya AI' and 'Mexipak 65', were grown in pots during the crop season in the field in NW Syria, a region with a Mediterranean climate. The experiment involved two treatments. Control plants were well-watered throughout the experiment (watering to 0.22 g water g-1 dry soil). In the second treatment, water was withheld from the plants until soil water content had decreased to 0.10 g water g-1 dry soil, the level that was maintained thereafter. Water use was measured by weighing the pots, and growth by destructive sampling. Growth of Katya and Mexipak was similar. Mexipak had a lower (though not significant at p < 0.05) plant water use efficiency (WUEp) in both treatments due to higher rates of water loss. On a leaf area basis differences in water use were especially high since Mexipak had a smaller total leaf area. In spite of a smaller investment in photosynthesizing area, Mexipak achieved similar growth as Katya. Carbon isotope discrimination and organic nitrogen concentration (both higher for Mexipak) suggest that Mexipak accomplished higher mean net photosynthetic rates with a higher mean leaf diffusive conductance, higher intercellular carbon dioxide partial pressure, and possibly a greater investment in the photosynthetic apparatus compared to Katya. Differences in carbon isotope discrimination suggest a larger difference in average photosynthetic WUE (net photosynthesis/transpiration) than in plant WUE. This could indicate that loss of carbon in respiration was greater in Katya. Gas exchange measurements on the youngest fully expanded leaves showed only minor differences between the cultivars. It is hypothesized that Mexipak, with a smaller total leaf area, is able to maintain high leaf conductance and photosynthesis for a longer period of time during the day or during the life span of leaves.

Photosynthesis and Remobilization of Dry Matter in Wheat as Affected by Progressive Drought Stress at Stem Elongation Stage

“…). In high‐yielding wheat genotypes, for instance, drought resulted in partitioning of a greater proportion of dry weight in stems instead of both leaves and roots (Veneklaas and Peacock ).…”

“…It has also been shown that genotypes may vary strongly in biomass partitioning to the different organs under drought conditions (Asch et al 1999). In high-yielding wheat genotypes, for instance, drought resulted in partitioning of a greater proportion of dry weight in stems instead of both leaves and roots (Veneklaas and Peacock 1994).…”

Yield and water use of wheat (Triticum aestivum) in a Mediterranean environment: Cultivar differences and sowing density effects

“…Differences in plant water use efficiency are related to differences in the ratio of photosynthesis and transpiration for potgrown wheat cultivars (Condon et al, 1990;Farquhar and Richards, 1984;Veneklaas and Peacock, 1994). The ratio of the photosynthetic rate and transpiration rate of the leaf has a major influence on plant water use efficiency.…”

Leaf age‐structure effects on plant water use and photosynthesis of two wheat cultivars

“…The photosynthesis measurements summarized in Table 1 were carried out under standardized conditions, so actual rates may differ as a result of different illumination, temperature etc. Results from a previous study (Veneklaas & Peacock, 1994) suggest tbat differences in respiration may account for differences in conversion of assimilates to biomass. Mexipak had 9 "o lower WUE^ but only 4% lower WUE^.…”