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Leaf Gas Exchange Characteristics of Jatropha as Affected by Nitrogen Supply, Leaf Age and Atmospheric Vapour Pressure Deficit
Author(s) -
Rajaona A. M.,
Brueck H.,
Asch F.
Publication year - 2013
Publication title -
journal of agronomy and crop science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.095
H-Index - 74
eISSN - 1439-037X
pISSN - 0931-2250
DOI - 10.1111/jac.12000
Subject(s) - vapour pressure deficit , photosynthesis , stomatal conductance , leaf area index , abiotic component , agronomy , compensation point , transpiration , chlorophyll , nitrogen , biology , environmental science , horticulture , chemistry , botany , ecology , organic chemistry
Facing a steadily increasing world energy demand, jatropha, among other energy crops, has been reported to potentially contribute to biofuel production. A basic characterisation of plant responses to abiotic environmental factors is important for assessing the model‐assisted potential of this plant in view of the many agro‐ecological zones in which jatropha is presently cultivated. Two pot experiments and two field studies were used to record gas exchange parameters in response to light, nitrogen supply, atmospheric vapour pressure deficit ( VPD ), leaf age and time of measurements. Variation of N supply from 0 to 16 m m resulted in lower rates of photosynthesis ( A ) and stomatal conductance ( g s ) of treatment 0 m m N compared with other N levels, whereas the light compensation point ( I C ), quantum yield ( QY ) and dark respiration rates ( R d ) were similar in all treatments. In the field, diurnal effects were evident with higher light‐saturated photosynthetic rate ( A max ) and QY and lower I C and R d in the morning than in the afternoon. Considering leaf age effects, fully expanded leaves had a lower A max compared with expanding leaves and this variation in leaf gas exchange was not related to changes in the chlorophyll index value ( SPAD ) which steadily increased with leaf age. Q Y of field and greenhouse plants varied from 0.023 to 0.037 and was substantially lower than in C 3 plants. A was positively correlated with g s in a hyperbolic function. A varied from 0.64 to 21.13 μmol m −2 s −1 and g s varied from 12 to 469 mmol m −2 s −1 . With increasing VPD , g s decreased, but this response differed between the field experiments and the two pot experiments which contrasted each other distinctively. Applying the inverse logistic function of Webb (Ecological Modeling, 56 (1991), 81), the maximal stomatal conductance of jatropha was in the range of 382 mmol m −2 s −1 and g s is predicted to be close to zero at 5 k P a. These data altogether indicate that light absorption characteristics of single leaves and carbohydrate status parameters should be investigated further to explain the low QY and the pronounced diurnal variation.