Light response of photosynthesis and stomatal conductance of rose leaves in the canopy profile: the effect of lighting on the adaxial and the abaxial sides

2020 ◽  
Vol 47 (7) ◽  
pp. 639
Author(s):  
Roberta Paradiso ◽  
Pieter H. B. de Visser ◽  
Carmen Arena ◽  
Leo F. M. Marcelis

We investigated the light response of leaf photosynthesis, stomatal conductance and optical properties in rose plants grown in a glasshouse with bending technique. Leaves were lighted from the adaxial or the abaxial side during measurements, performed in four positions in the upright and bent shoots: top leaves, middle leaves, bottom leaves, and bent shoot leaves. Moreover, the effect of the irradiation on the adaxial or abaxial leaf side on whole canopy photosynthesis was estimated through model simulation. No significant differences were found in light transmission, reflection and absorption of leaves and in photosynthesis light response curves among the four positions. In all the leaf positions, light absorption, stomatal conductance and photosynthesis were higher when leaves were lighted from the adaxial compared with the abaxial side. The model showed that a substantial part of the light absorbed by the crop originated from light reflected from the greenhouse floor, and thus the abaxial leaf properties have impact on whole crop light absorbance and photosynthesis. Simulations were performed for crops with leaf area index (LAI) 1, 2 and 3. Simulation at LAI 1 showed the highest reduction of simulated crop photosynthesis considering abaxial properties; however, to a lesser extent photosynthesis was also reduced at LAI 2 and 3. The overall results showed that the model may be helpful in designing crop systems for improved light utilisation by changing lamp position or level of leaf bending and pruning.

2019 ◽  
Author(s):  
Madhav P. Nepal ◽  
Virginia S. Berg

ABSTRACTPlants in stressful environments have evolved strategies to cope with fluctuating environmental conditions.Potentilla gracilis, also known as Alpine Cinquefoil, grows in alpine meadows of the Rocky Mountains (USA), and is subjected to wide ranges of temperature, light intensity and water availability on a time scale of minutes to days during the growing season. Leaves often freeze to a brittle state at night, are exposed to high radiation while still frosty, dehydrate to wilting during the following light period, and then repeat the cycle the following day. The main objective of this research was to determine the effect of night temperature on subsequent photosynthetic gas exchange inP. gracilis. We used a photosynthetic gas exchange system to compare assimilation and stomatal conductance from light response curves of cold-acclimatedP. gracilisfollowing warm and chilling nights, and for plants at different water potentials. From the light response curves, dark respiration, light compensation point, maximum assimilation, light saturation point, and inhibition of photosynthesis were determined and were compared among the same plants under varying conditions. Assimilation and stomatal conductance decreased with the fall in measurement temperature, following chilling nights, and with the severity of water stress. Low night temperature and high photon flux density during the daytime, which are very common during the growing season in the field, cause a reduction in photosynthesis of the plant. The probable underlying damage during inhibition is likely repairable indicating protection rather than damage. The cold nocturnal temperature, with its less efficient biochemical repair capabilities, may partly be responsible for the reduction in assimilation of the following day.P. gracilisspecies exhibited persistent acquired freezing tolerance; substantial photosynthetic productivity over a wide range of light intensity and temperature; and significant tolerance of, and rapid recovery from, severe drought; making a maximum use of often challenging resources.


1997 ◽  
Vol 75 (4) ◽  
pp. 562-567 ◽  
Author(s):  
Ken J. Greenway ◽  
Victor J. Lieffers

Calamagrostis canadensis is present in the understory of most boreal forest mixed-wood stands and can rapidly dominate an area once the overstory is removed. The nature of the photosynthetic response to light was studied by investigating the stomatal response to cycles of high and low fluence light, and by developing photosynthetic light response curves for sun- and shade-grown plants. Photosynthetic light response curves did not differ between sun- and shade-grown plants. However, higher stomatal conductances, at all light intensities, were found in shade-grown plants. Stomatal conductance tracked changes in light under intermittent high and low fluence light. Average rates of stomatal opening after a change from low to high light were greater than closing rates (23 vs. 17 mmol m−2 s−1/min). The faster opening response was negated by a 1 – to 2-min time lag between the onset of high light and the initiation of stomatal opening. Thus the time to reach 80% of maximal response did not differ between opening or closing. The photosynthetic system of C. canadensis is not particularly well adapted to intermittent light conditions. The poor performance in the understory of this apparently meadow-adapted photosynthetic system is offset by the gain in the ability to rapidly recolonize the site after disturbance. Key words: gas exchange, stomatal conductance, Calamagrostis canadensis, non-steady state photosynthesis, variable light.


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

2006 ◽  
Vol 30 (4) ◽  
pp. 670-678 ◽  
Author(s):  
Rafael Vasconcelos Ribeiro ◽  
Eduardo Caruso Machado ◽  
Ricardo Ferraz de Oliveira

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.


1995 ◽  
Vol 22 (1) ◽  
pp. 1 ◽  
Author(s):  
HG Jones ◽  
DO Hall ◽  
JE Corlett ◽  
A Massacci

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.


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