Considerations for Accurate Whole Plant Photosynthesis Measurement

2007 ◽  
Author(s):  
Noriko N.T TAKAHASHI ◽  
Peter P Ling ◽  
Jonathan M Frantz
Keyword(s):  
Whole Plant ◽  
Plant Photosynthesis

Responses of the apple plant to CO2 enrichment: changes in photosynthesis, sorbitol, other soluble sugars, and starch

1998 ◽  
Vol 25 (3) ◽  
pp. 293 ◽  
Author(s):  
Q. Pan ◽  
Z. Wang ◽  
B. Quebedeaux
Keyword(s):  
Elevated Co2 ◽  
Soluble Sugars ◽  
Co2 Enrichment ◽  
Carbohydrate Accumulation ◽  
Photosynthetic Rates ◽  
Mature Leaves ◽  
Whole Plant ◽  
Plant Photosynthesis ◽  
Apple Plant ◽  
Ambient Co2

There is no information on the effects of elevated [CO2] on whole-plant photosynthesis and carbohydrate metabolism in apple (Malus domestica Borkh.) and other sorbitol-translocating plants. Experiments were conducted in controlled growth chambers to evaluate how increases in [CO2] affect plant photosynthesis and carbon partitioning into soluble sugars and starch in apple leaves. Apple plants (cv. Gala), 1-year-old, were exposed to [CO2] of 200, 360, 700, 1000, and 1600 µL L-1 up to 8 d. Whole-plant net photosynthetic rates were analysed daily after [CO2] treatments. Newly expanded mature leaves were sampled at 1, 2, 4, and 8 d after [CO2] treatments for sorbitol, sucrose, glucose, fructose, and starch analysis. Midday whole-plant net photosynthetic rates increased linearly with increasing [CO2], but the differences in whole-plant photosynthesis between CO2-enrichment and ambient [CO2] treatments were less significant as apple plants acclimated to high atmospheric [CO2] for 8 d. Increases in [CO2] significantly increased sorbitol and starch, but did not affect sucrose concentrations. As a result, the ratios of starch to sorbitol and starch to sucrose at 8 d after [CO2] treatments were increased from 0.05 and 0.06 to 0.8 and 1.6 as [CO2] increased from ambient [CO2] (360 µL L-1) to 1000 µL L-1 [CO2], respectively. The sorbitol to sucrose ratio also increased from 1.3 to 2.2 as [CO2] increased from 360 to 1000 µL L-1. Elevated [CO2] enhanced the photosynthesis of apple plants and altered carbohydrate accumulation in mature leaves in favour of starch and sorbitol over sucrose.

scholarly journals Whole Plant Photosynthesis, Development, and Carbon Partitioning in Potato as a Function of Temperature

2006 ◽  
Vol 98 (5) ◽  
pp. 1195-1203 ◽  
Author(s):  
Dennis Timlin ◽  
S. M. Lutfor Rahman ◽  
Jeffery Baker ◽  
V. R. Reddy ◽  
David Fleisher ◽  
...  
Keyword(s):  
Carbon Partitioning ◽  
Whole Plant ◽  
Plant Photosynthesis

scholarly journals Postproduction Leaching Affects the Growing Medium and Respiration of Subirrigated Poinsettias

HortScience ◽  
2000 ◽  
Vol 35 (2) ◽  
pp. 250-253 ◽  
Author(s):  
Marc van Iersel
Keyword(s):  
Dark Respiration ◽  
Plant Stress ◽  
Middle Layer ◽  
Bottom Layer ◽  
Euphorbia Pulcherrima ◽  
Whole Plant ◽  
Growing Medium ◽  
Plant Photosynthesis ◽  
Saturated Medium ◽  
Fertilizer Solution

Poinsettias (Euphorbia pulcherrima Willd. ex Klotzsch) were grown in pots filled with 1.5 L of soilless growing medium and subirrigated daily with a fertilizer solution containing N at 210 mg·L-1 [electrical conductivity (EC) = 1.5 dS·m-1] for 128 days. After production, plants were placed in a whole-plant photosynthesis system and the effects of applying different volumes of water (0, 0.75, 1.5, and 3 L) to the top of the pots were quantified. Leaching with 0.75, 1.5, or 3 L of water reduced the EC in the top and middle layers of the growing medium. Applications of 0.75 or 1.5 L of water significantly increased the EC in the bottom third of the pots, where most of the root growth occurred. However, even in these treatments the EC in the bottom layer was only 2.6 dS·m-1 (saturated medium extraction method), which is well within the recommended range. The 0.75- and 1.5-L treatments also reduced the respiration rate of the plants by 20%, but none of the treatments had a significant effect on the photosynthesis of the plants. Regression analysis indicated a negative correlation between the EC of the bottom layer of the growing medium and dark respiration, while the EC of the top and middle layer had no significant effect on respiration. Although top watering can increase the EC in the bottom layer of the growing medium, this effect is unlikely to be large enough to cause significant plant stress and damage.

scholarly journals Whole-plant Photosynthesis of Containerized Hydrangeas and Abelias as Affected by Substrate Moisture Content

HortScience ◽  
2005 ◽  
Vol 40 (4) ◽  
pp. 1111D-1111 ◽  
Author(s):  
Marc W. van Iersel ◽  
Sue Dove
Keyword(s):  
Growth Rate ◽  
Drought Stress ◽  
Moisture Content ◽  
Water Potential ◽  
Photosynthetic Rate ◽  
Severe Drought ◽  
Whole Plant ◽  
Growing Medium ◽  
Plant Photosynthesis ◽  
Substrate Moisture

Efficient water use in nurseries is increasingly important. In recent years, new soil moisture sensors (ECH2O probes) have become available, making it possible to monitor the moisture content of the growing medium in containers. One piece of information that is lacking for fully-automated irrigation systems is how much water actually needs to be present in the growing medium to prevent detrimental effects of drought on plants. We determined the effect of substrate moisture on photosynthesis and plant water relations of hydrangea and abelia. Growth rates of these species were measured during two subsequent drying cycles to determine how drought affects the growth rate of these species. Whole-plant photosynthesis, an indicator of growth rate, of both species remained stable as the volumetric moisture content of the substrate dropped from 25% to 15%, with pronounced decreases in photosynthesis at lower substrate moisture levels. Abelias and hydrangeas wilted when the substrate moisture level dropped to 6.3% and 8.3%, respectively. At wilting, abelias had lower leaf water potential (–3.7 MPa) than hydrangeas (–1.8 MPa). After the plants were watered at the end of the first drying cycle, the photosynthesis of the plants did not recover to pre-stress rates, indicating that the drought stress caused a long-term reduction in photosynthesis. Despite the more severe drought stress in the abelias (both a lower substrate water content and lower water potential at wilting), abelias recovered better from drought than hydrangeas. After the plants were watered at the end of the first drying cycle, the photosynthetic rate of abelias recovered to ≈70%, while the photosynthetic rate of the hydrangeas recovered to only 62% of the pre-stress rate.

scholarly journals Relating Whole-plant Photosynthesis to Physiological Acclimations at Leaf and Cellular Scales under Drought Stress in Bedding Plants

2019 ◽  
Vol 144 (3) ◽  
pp. 201-208
Author(s):  
Krishna Nemali ◽  
Marc W. van Iersel
Keyword(s):  
Drought Stress ◽  
Net Photosynthesis ◽  
Carbon Gain ◽  
Bedding Plants ◽  
Drought Tolerant ◽  
Whole Plant ◽  
Increased Risk ◽  
Bedding Plant ◽  
Drought Conditions ◽  
Plant Photosynthesis

Bedding plants are at increased risk for exposure to drought stress during production because they are grown in small containers. Physiological mechanisms of bedding plants at leaf and cellular scales that regulate whole-plant photosynthesis under drought conditions are not well understood. This information can be useful for screening bedding plant cultivars with improved drought-tolerance and generate guidelines to mitigate drought stress during production. We subjected drought-sensitive salvia (Salvia splendens ‘Bonfire Red’) and drought-tolerant vinca (Catharanthus roseus ‘Cooler Peppermint’) to gradual drought stress inside whole-plant gas exchange chambers. Substrate water content (Θ), whole-plant net photosynthesis (Pn_avg), whole-plant respiration (Rd_avg), and daily carbon gain (DCG) were measured continuously, whereas stomatal conductance (gS) to water, leaf water (ΨL), osmotic (ΨS), and turgor (ΨP) potentials were measured at the start and end of the drought phase. In addition, ΨS was measured before exposure to stress and after thoroughly rehydrating plants. Dark-adapted quantum efficiency (dark-adapted ΦPSII) was measured after rehydrating plants. The results indicated that, at whole-plant scale, vinca continued to uptake water at lower Θ levels than the Θ level that resulted in wilting of salvia. There were no differences in Rd_avg; however, Pn_avg and DCG of salvia decreased at a higher Θ level than that of vinca. This indicated that salvia experienced drought stress at a higher Θ level than did vinca. At the leaf scale, there were no differences in ΨL; however, a more negative ΨS (P = 0.06) and significantly higher ΨP were observed in vinca (compared to salvia) under drought conditions. In addition, ΨS was not different between species before exposure to drought, whereas ΨS of rehydrated leaves after exposure to drought in vinca was significantly lower than that in salvia. Moreover, ΨS of rehydrated leaves after exposure to drought was significantly lower than that observed before exposure to drought in vinca. This indicated osmotic adjustment (OA) in vinca under drought conditions. Dark-adapted ΦPSII was lower in salvia than in vinca after exposure to drought, indicating damage to photosynthetic mechanisms. Our results suggested that increased OA likely helped to maintain higher ΨP under drought conditions and continuation of water uptake at lower Θ in vinca compared to salvia. In addition, healthier photosynthetic mechanisms of vinca (compared to salvia) under drought conditions likely resulted in its higher Pn_avg and DCG at lower Θ. Screening for OA and dark-adapted ΦPSII may be useful for developing drought-tolerant bedding plant cultivars.

scholarly journals Drought tolerance in Zn-deficient red cabbage (Brassica oleracea L. var. capitata f. rubra) plants

2010 ◽  
Vol 37 (No. 3) ◽  
pp. 88-98 ◽  
Author(s):  
R. Hajiboland ◽  
H. Amirazad
Keyword(s):  
Photosynthetic Apparatus ◽  
Zn Deficiency ◽  
Red Cabbage ◽  
And Zn Deficiency ◽  
Whole Plant ◽  
Zn Content ◽  
Drought Conditions ◽  
Plant Photosynthesis ◽  
Use Efficiency ◽  
Net Assimilation

Effects of Zn deficiency were studied in red cabbage plants under well-watered or drought conditions. Impairment of growth due to Zn deficiency was higher under drought compared with well-watered conditions. Drought stress caused a drastic decline in Zn content and led to a damage of photosynthetic apparatus in Zn-deficient but not Zn-sufficient leaves. Net assimilation and transpiration rate were strongly reduced under Zn deficiency and drought conditions following reduction of stomatal conductance. Activity of antioxidant enzymes, with the exception of superoxide dismutase, increased under Zn deficiency conditions, while drought enhanced activity of all studied enzymes concomitant with accumulation of malondialdehyde and H<sub>2</sub>O<sub>2</sub>. The intensifying effect of drought on Zn-deficient leaves could be explained by impaired leaf photochemical events, reduction of whole plant photosynthesis and imbalance between production and scavenging of reactive oxygen species. Water use efficiency, water and osmotic potential of drought-stressed plants were higher under low compared with adequate Zn supply, however, these parameters were not critical for plant growth response under combinative effect of drought and Zn deficiency.

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