poster - International Conference of Agricultural Engineering

coordinates are latitude 7°13'11'', longitude 35º53'31'' west and altitude of 547.56 m.
According to the National Institute of Meteorology (INMET), the city has an annual rainfall of
802.7 mm, maximum temperature of 27.5 °C, minimum 19.2 °C and relative humidity of 83%.
The search was performed using polyethylene vessel with a capacity of 1.5 kg of substrate
Regossolo Neolithic Eutrophic fertilized according Novais et al. (1991). Were sown in each
vessel, three seeds, leaving only one plant per pot after thinning, which occurred five days
after emergence. We used a completely randomized design in a 4x5 factorial (genotype x
salinity), with four replications. Treatments consisted of four levels of salinity of irrigation
water (1.5, 3.0, 4.5 and 6.0 dSm -1 ), based on the results of Ayers and Westcot (1999) and
genotypes (G ) were used (G1) MNCO1-649F-1-3 (G2) BRS-Juruá (G3) MNCO2-675F, 4-9,
(G4) MNCO3-7-736F and (G5) MNCO2-5-684F 6, granted by Embrapa Mid-North, Center for
reference in research with the improvement of cowpea, and production of new cultivars,
located in the city of Teresina, Piauí State, and specially developed for cultivation in the
climatic conditions prevailing in the Brazilian Northeast. Irrigation was performed daily with
water from the supply network's campus UFCG, to be pruned, if from this, the water used for
irrigation had different levels of salinity, according to the treatments. The salinity levels were
evaluated salts obtained by mixing Na, Ca, and Mg. Evaluations were performed at 40 days
after emergence (DAE), when samples were collected from leaf tissues of plants, brought to
the Laboratory of Irrigation and Salinity (LIS) of the Center for Technology and Natural
Resources (CTRN), Federal University of Campina Grande ( UFCG), processed and
analyzed the contents of chlorophyll a, chlorophyll b, total chlorophyll and carotenoids, and
the ratio chlorophyll a / b and total chlorophyll / carotenoids. Extractor as pigments used is
80% acetone, and the absorbance readings determined at 470, 647 and 663 nm. The
pigment content was determined by equations (Equations 1, 2, 3 and 4) conditions
(Lichtenthaler & Welburn, 1983), and the data was analyzed by F test and adjusted
regression models with the regression coefficient.
Equation 1: Cl a = (12,25 x A 663 ) – (2,79 x A 647 )
Equation 2: Cl b = (21,50 x A 647 ) – (5,10 x A 663 )
Equation 3: Cl total = (7,15 x A 663 ) + (18,71 x A 647 )
Equation 4: Carotenoids = (1000 x A 470 – 1,82 x Cla – 85,02 x Clb) / 198
3. Results and Discussion
Analysis of variance in showed significant interaction between the two limiting factors
evaluated, genotype and salinity levels for any of the variables. Regarding the content of
chlorophyll b, total chlorophyll and carotenoids, we obtained a significant response to the
isolated factors. As for the content of chlorophyll a relative total chlorophyll / carotenoids,
only the levels of salinity were significant, whereas the chlorophyll a / chlorophyll b, only the
factor genotype was significant at 1%. Separately, there was significance (P ≤ 0.05) for
salinity levels and genotypes on all variables. The content of chlorophyll a higher than were
those of chlorophyll b, for all genotypes (FIGURE 2). The genotype-675F-MNCO2 4-9
showed the smallest amounts of photosynthetic pigments, while the genotype MNCO1-649F-
1-3 showed the highest levels of pigments, showing the differential sensitivity to salt levels.
Regression analysis showed negative linear response to the levels of photosynthetic
pigments (FIGURE 3), there was a gradual decrease in the levels of pigments with
increasing salt concentration in irrigation water, showing likely that there was a symbiosis of
sensitivity to salt stress, which is reflected in the N availability to plants and consequently in
the production of pigments responsible for capturing CO 2 and light for photosynthesis. The
content of chlorophyll a has been reduced linearly with increasing salinity of irrigation water
(FIGURE 3). Comparing the values of that pigment in the higher salinity level (6 dSm -1 ) been