The Influence of Water Stress on Stem and Leaf Photosynthesis in Glycine Max and Sparteum Junceum (Leguminosae)

Abstract

Stem and leaf photosynthesis were measured in Glycine max var. essex (soybean) and Sparteum junceum (Spanish broom). The significance of stem photosynthesis to whole plant growth was evaluated by blocking stem photosynthesis with black straw sections. The growth of S. junceum was reduced by 18% when black straws were used in comparison to clear straws. The whole plant growth of G. max was not influenced by blocking the stem carbon contribution. Mean midday leaf photosynthesis was 12 μmol CO2 m–2 s–1 and 17 μmol CO2 m–2 s–1 for G. max and 5. junceum, respectively. Mean midday stem photosynthesis of S. junceum was 6.5 μmol CO2 m–2 s–1; however, positive net photosynthesis did not occur in G. max stems. Water stress caused a proportionally greater decrease in leaf photosynthesis compared to that of stems during diurnal cycles of photosynthesis in S. junceum. As a result the contribution to canopy carbon gain by stem photosynthesis increased from 38% to 48% of the total plant carbon gain under reduced water availability.

Diurnal and seasonal patterns of gas exchange and carbon gain contribution of leaves and stems of Justicia californica in the Sonoran Desert

“…Stems contributed 23% of the total carbon gain, but for about 7 months, they were the only source of carbon gain. Similarly, for several species of the Mojave and Sonoran Deserts, the relative carbon gain contribution of stems and leaves depended on their area and longevity Nilsen and Bao, 1990).…”

The Existence of Bark and Stem Photosynthesis in Woody Plants and Its Significance for the Overall Carbon Gain. An Eco-Physiological and Ecological Approach

“…Most of the available positive netphotosynthesis data were obtained from isolated chlorenchymes or peeled tissues. Depending on the methods, CO 2 uptake or 02 release were between 6 Ilmollm2/s and 30 Ilmollm2/s (for Spartium, Ilex, Psorothamnus, Fagus and Syringa: Nilsen et al 1989;Nilsen and Bao 1990;Bossard and Rejmanek 1992;Nilsen et al 1993;Pilarski 1993;Schmidt et al2000).…”

Strong Response of Stem Photosynthesis to Defoliation in Mikania micrantha Highlights the Contribution of Phenotypic Plasticity to Plant Invasiveness

“…However, in some cases, a reduction in leaf photosynthesis can be compensated for by the mobilization of stored carbohydrates, reallocation of carbon or stem photosynthesis (Eyles et al, 2009). Compared with leaf photosynthesis, stem photosynthesis is less vulnerable to environmental stresses such as seasonal changes and reduced water availability; therefore, stem photosynthesis is able to compensate for the loss of leaf photosynthesis under stress conditions (Nilsen and Bao, 1990;Nilsen et al, 1993). In M. micrantha, the response of soluble sugars to defoliation treatment was slower than the response of stem photosynthesis (Figure 6), suggesting that stem photosynthesis rather than the stored carbohydrates is preferentially used to compensate for the decrease in leaf photosynthesis.…”