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 Photosynthesis, Respiration, and Water Relations of Vinca and Salvia Subjected to Moisture Stress

HortScience ◽  
2004 ◽  
Vol 39 (4) ◽  
pp. 896B-896
Author(s):  
Krishna Nemali* ◽  
Marc van Iersel
Keyword(s):  
Growth Rate ◽  
Gas Exchange ◽  
Water Relations ◽  
Moisture Stress ◽  
Bedding Plants ◽  
Salvia Splendens ◽  
Whole Plant ◽  
Growing Medium ◽  
Bedding Plant ◽  
Substrate Moisture

Subjecting bedding plants to non-lethal moisture stress is an established irrigation practice for bedding plants; however information on physiological responses of bedding plants to moisture stress is limited. We examined the CO2 exchange rates (CER) and water relations of salvia (Salvia splendens) and vinca (Catharanthus roseus) during moisture stress. Seedlings of both species were grown from seed in 7-L trays containing a soilless growing medium. After plants completely covered the trays, they were irrigated and shifted into whole-plant gas exchange chambers (27 °C and daily light integral of 7.5 mol/m2) arranged inside a growth chamber. Inside the gas exchange chambers, the growing medium was allowed to dry and plants were re-watered after wilting. Results from this study indicate that the growth rate (moles of CO2 gained by plants in a day) of salvia was higher than vinca before experiencing moisture stress; however the volumetric moisture content of the growing medium at which plant growth decreased was higher for salvia than for vinca. During moisture stress, the decrease in growth rate of salvia was gradual and that of vinca was rapid. After re-watering the plants, leaf water potential (ΨL) and growth rate of vinca revived completely, and ΨL of salvia remained low (more negative), whereas its growth rate revived completely. This study shows that bedding plant species respond differently to moisture stress, particularly with respect to the critical substrate moisture level for initiating moisture stress and the rate of development of moisture stress.

Photosynthesis and Growth of Magnolia × soulangiana in Response to Consecutive Drought Stress

HortScience ◽  
1998 ◽  
Vol 33 (3) ◽  
pp. 539b-539
Author(s):  
R.T. Fernandez ◽  
R.E. Schutzki
Keyword(s):  
Soil Moisture ◽  
Drought Stress ◽  
Moisture Content ◽  
Shoot Growth ◽  
Soil Moisture Content ◽  
Growth Characteristics ◽  
Leaf Photosynthesis ◽  
Short Term ◽  
Whole Plant ◽  
Plant Photosynthesis

Responses of Magnolia × soulangiana `Jane' to consecutive short-term drought stresses were evaluated in this study. Plants were received from a commercial nursery in 19-L containers in a 4:1 pine bark:sand media. In Oct. 1997, plants were exposed to one, two or three consecutive 3-day drought stress periods, each separated by one rewatering period. There were 48 total plants with eight replicates per treatment for each stress period. Following each stress period, a group of eight control and eight stressed plants were planted in the field and well-watered to monitor recovery from each stress duration. Whole-plant photosynthesis, leaf photosynthesis, shoot growth, and soil moisture content were measured approximately every 2 days during the stress periods. Leaf photosynthesis, shoot growth, and leaf defoliation rate were monitored for recovering plants. Few differences in growth were noticed except more rapid defoliation with onset of autumn for the three 3-day stressed plants. Whole-plant and leaf photosynthesis were reduced by day 3 of the first 3-day stress for drought-stressed plants and remained lower while plants were under stress. After release from stress, photosynthesis returned to control levels for plants receiving one and two 3-day stress treatments in ≈1 week, while it was more than 3 weeks until recovery for plants receiving three 3-day stress treatments. Plants will be evaluated in Spring 1998 for bloom and growth characteristics.

scholarly journals Mechanisms of xylem hydraulic recovery after drought in Eucalyptus saligna

2021 ◽  
Author(s):  
Alice Gauthey ◽  
Jennifer Peters ◽  
Rosana López ◽  
Madeline Carins Murphy ◽  
Celia M. Rodriguez-Dominguez ◽  
...  
Keyword(s):  
Drought Stress ◽  
Severe Drought ◽  
Stem Water Potential ◽  
Micro Computed Tomography ◽  
Time Intervals ◽  
Eucalyptus Saligna ◽  
Whole Plant ◽  
Xylem Tissue ◽  
Stem Water

The mechanisms by which woody plants recover xylem hydraulic capacity after drought stress are not well understood, particularly with regard to the role of embolism refilling. We evaluated the recovery of xylem hydraulic capacity in young Eucalyptus saligna plants exposed to cycles of drought stress and rewatering. Plants were exposed to moderate and severe drought stress treatments, with recovery monitored at time intervals from 24 hrs to 6 months after rewatering. The percentage loss of xylem vessels due to embolism (PLV) was quantified at each time point using micro-computed tomography with stem water potential (Ψx) and whole plant transpiration (Eplant) measured prior to scans. Plants exposed to severe drought stress suffered high levels of embolism (47.38 ± 10.97 % PLV) and almost complete canopy loss. No evidence of embolism refilling was observed at 24 hrs, one week, or three weeks after rewatering despite rapid recovery in Ψx. Recovery of hydraulic capacity was achieved over a 6-month period by growth of new xylem tissue, with canopy leaf area and Eplant recovering over the same period. These findings indicate that E. saligna recovers slowly from severe drought stress, with potential for embolism to persist in the xylem for many months after rainfall.

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 Characteristics of Leaf Water Potential and Photosynthetic Rate of Blueberry Plants Grown Under Drought Stress

2011 ◽  
Vol 10 (4) ◽  
pp. 485-490 ◽  
Author(s):  
Naomi Horiuchi ◽  
Naoko Kameari ◽  
Jingai Che ◽  
Sakae Suzuki ◽  
Tadashi Hirasawa ◽  
...  
Keyword(s):  
Drought Stress ◽  
Water Potential ◽  
Leaf Water Potential ◽  
Photosynthetic Rate ◽  
Leaf Water

scholarly journals Effect of Three Water Regimes on the Physiological and Anatomical Structure of Stem and Leaves of Different Citrus Rootstocks with Distinct Degrees of Tolerance to Drought Stress

Horticulturae ◽  
2021 ◽  
Vol 7 (12) ◽  
pp. 554
Author(s):  
Waqar Shafqat ◽  
Yasser S. A. Mazrou ◽  
Sami-ur-Rehman ◽  
Yasser Nehela ◽  
Sufian Ikram ◽  
...  
Keyword(s):  
Drought Stress ◽  
Plant Growth ◽  
Moisture Content ◽  
Vascular Bundle ◽  
Anatomical Structure ◽  
Severe Drought ◽  
Plant Water ◽  
Sour Orange ◽  
Cell Area ◽  
Cell Thickness

Citrus is grown globally throughout the subtropics and semi-arid to humid tropics. Abiotic stresses such as soil water deficit negatively affect plant growth, physiology, biochemistry, and anatomy. Herein, we investigated the effect(s) of three water regimes (control, moderate drought, and severe drought) on the physiological and anatomical structure of 10 different citrus rootstocks with different degrees of tolerance to drought stress. Brazilian sour orange and Gadha dahi performed well by avoiding desiccation and maintaining plant growth, plant water status, and biochemical characters, while Rangpur Poona nucellar (C. limonia) and Sunki × bentake were the most sensitive rootstocks at all stress conditions. At severe water stress, the highest root length (24.33 ± 0.58), shoot length (17.00 ± 1.00), root moisture content (57.67 ± 1.53), shoot moisture content (64.59 ± 1.71), and plant water potential (−1.57 ± 0.03) was observed in tolerant genotype, Brazilian sour orange. Likewise, chlorophyll a (2.70 ± 0.06), chlorophyll b (0.87 ± 0.06) and carotenoids (0.69 ± 0.08) were higher in the same genotype. The lowest H2O2 content (77.00 ± 1.00) and highest proline content (0.51 ± 0.06) were also recorded by Brazilian sour orange. The tolerance mechanism of tolerant genotypes was elucidated by modification in anatomical structures. Stem anatomy at severe drought, 27.5% increase in epidermal cell thickness, 25.4% in vascular bundle length, 30.5% in xylem thickness, 27.7% in the phloem cell area, 8% in the pith cell area, and 43.4% in cortical thickness were also observed in tolerant genotypes. Likewise, leaf anatomy showed an increase of 27.9% in epidermal cell thickness, 11.4% in vascular bundle length, 21% in xylem thickness, and 15% in phloem cell area in tolerant genotypes compared with sensitive ones. These modifications in tolerant genotypes enabled them to maintain steady nutrient transport while reducing the risk of embolisms, increasing water-flow resistance, and constant transport of nutrients across.

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.

Effect of irradiance on growth and photosynthesis of Populus × euramericana clones

1978 ◽  
Vol 8 (1) ◽  
pp. 94-99 ◽  
Author(s):  
F. E. Fasehun
Keyword(s):  
Growth Rate ◽  
Laboratory Experiments ◽  
Dark Respiration ◽  
High Irradiance ◽  
Dark Respiration Rate ◽  
Photosynthetic Rates ◽  
Populus Euramericana ◽  
Unit Leaf ◽  
Whole Plant ◽  
Plant Photosynthesis

Greenhouse and laboratory experiments were conducted to determine the effect of irradiance level on growth and photosynthesis of three Populus × euramericana clones selected to exhibit differences in growth rate when grown under full sunlight. Individual plants were started from apical cuttings and grown in the greenhouse for 13 weeks under three levels of shading (37%, 75%, and 100% full light). Rates of leaf and whole plant photosynthesis and dark respiration were measured with an infrared gas analyzer.Clone 5323 grew relatively well under all irradiance levels, and the older leaves of this clone had the highest photosynthetic rates per unit leaf area under the higher growth irradiances. Clone 5326, which had the least growth, also had the lowest per-plant photosynthesis rate under all irradiance levels. Clone 5321 had per-plant photosynthetic rates comparable with those of clone 5323 but a higher dark respiration rate when grown at the high irradiance levels.

scholarly journals The Effect of Calcium on Photosynthetic Rate due to ABA and Proline Behaviour of Oil Palm (Elaeis guineensis Jacq.) Seedlings under Drought Conditions

2019 ◽  
Vol 34 (1) ◽  
pp. 31
Author(s):  
Endah Nurwahyuni ◽  
Eka Tarwaca Susila Putra
Keyword(s):  
Drought Stress ◽  
Nitrate Reductase ◽  
Photosynthetic Rate ◽  
Oil Palm ◽  
Nitrate Reductase Activity ◽  
Reductase Activity ◽  
Measurement Data ◽  
Stomatal Aperture ◽  
Carotenoid Content ◽  
Severe Drought

<p>Planting drought-resistance plants in terms of agronomy, such as induction of plant tolerance using calcium is assumed to be able to solve the climate anomaly problem. Calcium is known as an element that plays an essential role in determining the response of plant resistance to drought through biochemical activity. This study aimed to determine the role of calcium in changing photosynthesis activity in order to increase the resistance to drought stress. The treatment was arranged in factorial of 3 x 4 in a split plot Randomized Complete Block Design replicated three times. The first factor was the dose of calcium application consisted of 0 (control/without calcium), 0.04, 0.08 and 0.12 g. The second factor was the intensity of drought stress, which referred to the Fraction of Transpirable Soil Water method consisted of 1 (control/field capacity), 0.35 (moderate drought) and 0.15 (severe drought). The measurement data of stomatal aperture, Abscisic Acid (ABA) content, chlorophyll content, carotenoid content, proline content, nitrate reductase activity and photosynthesis rate that fulfill the assumption of homogeneity and normality were analyzed using variance at 95% accuracy and continued using DMRT. Moreover, regression analysis were determined of relationship between the treatment and parameters. The results revealed that drought resulted in a decline in leaf water potential and stomatal aperture. The effects of calcium on chlorophyll and carotenoid under drought stress could not be explained in this study. However, the application of calcium has a significant effect on decreased ABA, increased proline and nitrate reductase activity resulting in an increase in the photosynthetic rate of oil palm seeds in drought stress.</p>

scholarly journals Drought Stress Can Produce Small but not Compact Marigolds

HortScience ◽  
2004 ◽  
Vol 39 (6) ◽  
pp. 1298-1301 ◽  
Author(s):  
Marc W. van Iersel ◽  
Krishna S. Nemali
Keyword(s):  
Drought Stress ◽  
Moisture Content ◽  
Leaf Area ◽  
Plant Height ◽  
Growth Parameters ◽  
Unit Length ◽  
Dry Mass ◽  
Stem Length ◽  
Bedding Plants ◽  
Growing Medium

We examined the effectiveness of an elevated capillary mat system to maintain constant and different moisture levels in the growing medium and verify the potential of drought stress conditioning in producing small and compact bedding plants. To differentiate between plant height and compactness, we determined compactness as the leaf area or dry mass per unit stem length. Marigold `Queen Sophia' (Tagetes erecta L.) seedlings were grown in square, 9-cm-wide, 10-cm-high containers filled with a soilless growing medium. A capillary mat was laid on top of a greenhouse bench which was raised by 15 cm on one side compared to the other side to create an elevation effect. Seedlings were subirrigated by immersing the low end of the capillary mat in a reservoir of water. The amount of water moving to the higher end of the mat progressively decreased with elevation. The moisture content in the growing medium averaged from 26 to 294 mL/pot at different elevations. Regression analysis indicated that growth parameters including, shoot dry mass, leaf area, leaf number, and plant height decreased linearly with decreasing soil moisture content in the growing medium. Of all the measured growth parameters, plant height was found to be least sensitive to decreasing moisture content in the growing medium. Plants in high moisture treatments had more dry mass and leaf area per unit length of the stem compared to those in low moisture treatments. Our results indicate that drought stress can produce small, but not truly compact bedding plants.

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