“VI Jornadas Integradas de Investigación y Extensión de la FCA”
“Iº Jornada de Enseñanza en las Ciencias Agropecuarias” -3 y 4 de noviembre de 2015
Estimation of chlorophyll content in oregano leaves using a
portable chlorophyll meter: relationship with mesophyll
thickness
PereyraM.S.1, DavidencoV.1, NúñezS.B.1, Argüello J.A.1
Total chlorophyll content (Chl) measurement yields direct information on photosynthesis potential and
provides an indirect measure of plant's physiological stress. Several studies have made satisfactory estimates
of Chl with portable meters based on the leaf optical properties varying the fitting equation. As a leaf
develops, growth conditions generate changes in pigment concentration, photosynthesis rate, leaf anatomy
and optical properties. Thus, specific measurement protocols are required for each species, meter and growth
condition. Despite numerous related studies, the information on the subject in oregano leaves is scarce. The
objectives were to evaluate the capacity of the chlorophyll meter CCM 200 plus to estimate the Total
chlorophyll contentin Origanumvulgare ssp. Hirtum Iestw. to elaborate a calibration model adapted to the
species and evaluate the effect of mesophyll thickness (MT) on the readings. The research was based on leaf
age (Young, Mature and Senescent leaves), including a wide range of Chl, MTand leaves from different
strata within the plant to achieve a more accurate determination of Chl and improve the fitting of the meter.
This study provides the first insights into thecalibration of the CCM 200 plus chlorophyll meterin oregano
leaves under field conditions, and itsrelationship with leaf age and mesophyll thickness.The CCM 200 plus
meter provided goodestimates of chlorophyll content for all leaves,independent of leaf age, position within
the plant and phenological stage. Nevertheless, the meterloses efficiency with increasing chlorophyll
concentrationand/or increased leaf thickness. Asthe leaves develop mesophyll thickness andchlorophyll
content increases. The increasedthickness given by greater development of spongyparenchyma leads to
higher variability in thereadings and linear relationship distortion. It is forthis reason that the calibration
model thatresponds to a logistic function was the equationthat provides the best fit and representation in the
ratio between instrument readings and chlorophyllconcentration [Chl=0.343/(1+1.925(-0.069x)].
Furthermore, it adapts to broad data ranges and any leaf typology, according to ontogenetic ageand position
in the plant.Despite the loss of efficiency mentioned, the CCM 200 plus portable meter is a very useful tool
to estimate chlorophyll content, aiming to relate these values with different situations of environmental
stress, nutritional management programsand genetic improvement systems.
Palabras clave: Origanumvulgare L., CCM 200 plus, thickness index, spongy parenchyma.
1
Fisiología Vegetal. FCA. [email protected]
Trabajo presentado en “16th International CongressonPhotobiology”. 2014