Drought Enhances Stomatal Closure in Response to Shading in Sorghum (Sorghum bicolor) and in Millet (Pennisetum americanum)

1995 ◽  
Vol 22 (1) ◽  
pp. 1 ◽  
Author(s):  
HG Jones ◽  
DO Hall ◽  
JE Corlett ◽  
A Massacci
Keyword(s):  
Sorghum Bicolor ◽  
Water Status ◽  
Stomatal Closure ◽  
Light Response ◽  
Pennisetum Americanum ◽  
Crop Water ◽  
Response Curves ◽  
Early Stages ◽  
Light Response Curves ◽  
Sorghum Bicolor L

When field-grown sorghum (Sorghum bicolor (L.) Moench) and millet (Pennisetum americanum (L.) Leeke) plants are subjected to drought, the speed of stomatal closure in response to darkness is enhanced in comparison with the speed observed in well-irrigated control plants. This shade-induced closure is most apparent at early stages of desiccation and is not rapidly reversible. These results need to be considered when developing protocols for the measurement of photosynthetic light response curves in the field. The sensitivity to crop water status of this stomatal closure response potentially provides a very valuable means for detection of the early stages of soil drying, and may also provide opportunities for screening different varieties for their adaptation to drought conditions.

DROUGHT RESISTANCE OF SORGHUM BICOLOR. 1. DROUGHT AVOIDANCE MECHANISMS RELATED TO LEAF WATER STATUS

1978 ◽  
Vol 58 (1) ◽  
pp. 213-224 ◽  
Author(s):  
DARRYL G. STOUT ◽  
GRAHAM M. SIMPSON
Keyword(s):  
Sorghum Bicolor ◽  
Water Status ◽  
Stomatal Closure ◽  
Irrigation Treatment ◽  
Ageing Effect ◽  
Leaf Water Status ◽  
Drought Avoidance ◽  
Diffusive Resistance ◽  
The Difference ◽  
Sorghum Bicolor L

Leaf ψs (osmotic potential) of two Sorghum bicolor (L.) Moench cultivars M35 and NK300 given an irrigation treatment decreased with increasing plant age. Following 3 wk without irrigation, leaf ψs of plants of both cultivars was lower than that in irrigated controls. Following 9 wk without irrigation, leaf ψs of M35 plants was still significantly lower than that in irrigated controls; but in NK300 the difference in leaf ψs between irrigated and non-irrigated plants was no longer significant due to an ageing effect changing leaf ψs less in non-irrigated than in irrigated plants. Evidence indicated that leaf ψs decreased due to osmoregulation, a drought avoidance mechanism, resulting in formation of more osmotically active cellular solutes. Greater leaf senescence of non-irrigated plants is a second drought avoidance mechanism used by sorghum to decrease transpiration requirements. Leaf diffusive resistance measurements indicated open stomata in both irrigated and non-irrigated plants so that under the imposed water stress conditions stomatal closure was not affecting the transpiration requirement.

Physiological ecology of lodgepole pine (Pinuscontorta) in an enriched CO2 environment

1985 ◽  
Vol 15 (2) ◽  
pp. 417-421 ◽  
Author(s):  
K. O. Higginbotham ◽  
J. M. Mayo ◽  
S. L'Hirondelle ◽  
D. K. Krystofiak
Keyword(s):  
Surface Area ◽  
Leaf Surface ◽  
Lodgepole Pine ◽  
Stomatal Closure ◽  
Light Response ◽  
Net Photosynthesis ◽  
Response Curves ◽  
Light Response Curves ◽  
Leaf Surface Area ◽  
Photosynthetic Responses

Relatively little work has been done to evaluate the effects of chronically high levels of carbon dioxide on growth and physiology of woody plants. In this study, seedlings of lodgepole pine (Pinuscontorta Dougl. var. latifoliaEngelm.) were grown for 5-month periods at 330, 1000, or 2000 μL CO2•L−1. Height growth; leaf area production; biomass of leaves, stems, and roots; and photosynthetic responses to changing light, moisture, and CO2 concentration were measured. Significant differences between treatments were found in mean seedling height on all measurement dates. Seedlings grown at 1000 μL CO2•L−1 were tallest, with seedlings grown in 2000 μL•L−1 intermediate between the control (330 μL•L−1) and 1000 μL•L−1 treatments. The same relationship was found in production of total leaf surface area. Increased leaf surface area yields a productive advantage to seedlings grown at concentrations of CO2 up to 2000 μL•L−1 even if no increase in net photosynthesis is assumed. Biomass of stems, roots, and secondary leaves was increased in both elevated CO2 conditions, with root biomass approximately 15 times greater in seedlings grown at 1000 μL•L−1 than in those grown at 330 μL•CO2•L−1. Stomatal resistances were essentially the same for all treatments, indicating no CO2-induced stomatal closure to at least 2000 μL•L−1. Photosynthetic Vmax (milligrams per square decimetre per hour) for light response curves varied with CO2 concentration. If results are extrapolated beyond a 5-month period and into field conditions, it appears that size of trees, interactions with competitors, and ecological role of the species might be altered.

The influence of the hemiparasitic angiosperm Cassytha pubescens on photosynthesis of its host Cytisus scoparius

2010 ◽  
Vol 37 (1) ◽  
pp. 14 ◽  
Author(s):  
Hao Shen ◽  
Jane N. Prider ◽  
José M. Facelli ◽  
Jennifer R. Watling
Keyword(s):  
Carbon Fixation ◽  
Stomatal Closure ◽  
Light Response ◽  
Poor Performance ◽  
Quantum Yields ◽  
Cytisus Scoparius ◽  
Response Curves ◽  
Photosynthetic Rates ◽  
Invasive Shrub ◽  
Light Response Curves

Infection with Cassytha pubescens R.Br, an Australian native hemiparasitic plant, can lead to death of the invasive shrub, Cytisus scoparius L. Link (Scotch broom). We examined the influence of C. pubescens on photosynthetic physiology of C. scoparius to determine whether this might contribute to death of infected plants. Infected C. scoparius had significantly lower photosynthetic rates, stomatal conductance and transpiration, and higher Ci (internal [CO2]), than uninfected plants. Rapid light response curves, determined using chlorophyll fluorescence, indicated significantly lower light-saturated electron transport rates and lower quantum yields for infected plants relative to uninfected plants. However, Rubisco content did not differ between infected and uninfected plants, suggesting the lower photosynthetic rates were most likely due to stomatal closure, rather than lower photosynthetic capacity. As a consequence of lower assimilation rates, PSII efficiency was lower in infected plants than uninfected plants across the diurnal cycle. Infected plants also had significantly lower pre-dawn Fv/Fm values and slower recovery from exposure to high light than uninfected plants. Our results suggest that infected C. scoparius are more susceptible to photodamage than uninfected plants. Combined with lower carbon fixation rates, this could contribute to the poor performance and even death of infected plants.

Photosynthetic light-response curves

Planta ◽  
1993 ◽  
Vol 189 (2) ◽  
Author(s):  
E. �gren ◽  
J.R. Evans
Keyword(s):  
Light Response ◽  
Response Curves ◽  
Light Response Curves

scholarly journals Temperature response of photosynthesis and its interaction with light intensity in sweet orange leaf discs under non-photorespiratory condition

2006 ◽  
Vol 30 (4) ◽  
pp. 670-678 ◽  
Author(s):  
Rafael Vasconcelos Ribeiro ◽  
Eduardo Caruso Machado ◽  
Ricardo Ferraz de Oliveira
Keyword(s):  
Sweet Orange ◽  
Photochemical Efficiency ◽  
Temperature Response ◽  
Light Response ◽  
Photon Flux ◽  
O2 Evolution ◽  
Response Curves ◽  
Leaf Discs ◽  
Light Response Curves ◽  
Heat Effects

This study aimed to evaluate the response of photosynthesis (A), given by photosynthetic O2 evolution, to increasing temperature from 25 to 50ºC in sweet orange (Citrus sinensis (L.) Osbeck) leaf discs under non-photorespiring conditions. In order to evaluate the response of gross photosynthesis to temperature and the balance between photosynthetic and respiratory activities, respiration (Rd) rates were also measured, i.e. the O2 uptake in each temperature. In addition, light response curves of photosynthesis were performed by varying the photosynthetic photon flux density (PPFD) from 0 to 1160 µmol m-2 s-1 at 25 and 40ºC. The highest A values were observed at 35 and 40ºC, whereas the highest Rd values were noticed at 50ºC. A higher relationship A/Rd was found at 30 and 35ºC, suggesting an optimum temperature of 35ºC when considering the balance between photosynthesis and respiration under non-photorespiring condition. Overall, heat effects on plant metabolism were more evident when evaluating the relationship A/Rd. In light response curves, higher A values were also found at 40ºC under PPFD higher than 300 µmol m-2 s-1. Light saturation point of photosynthesis was increased at 40ºC, without significant change of quantum efficiency under low PPFD. Respiration was also enhanced at 40ºC, and as a consequence, the light compensation point increased. The better photosynthetic performance at 35-40ºC was supported by higher photochemical efficiency in both light and temperature response curves. The temperature-dependence of photosynthesis was affected by growth temperature, i.e. a high air temperature during plant growth is a probable factor leading to a higher photosynthetic tolerance to heat stress.

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