Photosynthetic pigments accumulation and some growth indices of cowpea, maize and tomato in response to interspecific and intraspecific competition stress

摘要

This study aimed at investigating the photosynthetic pigment accumulation and some growth indices of cowpea, maize and tomato in response to interspecific and intraspecific competition stress. The study was carried out under a screen-house to minimize extraneous factors such as pests and rodents using a randomized complete block design (RCBD). Seeds of cowpea, maize and tomato were collected from the Department of Crop Production and Protection, Faculty of Agriculture, Obafemi Awolowo University, Ile Ife, Osun state, Nigeria. These seeds were planted at a depth of about 3 mm below the soil. The seeds were sown at the rate of six seeds per pot in the monoculture, while in the pots designed for the mixed cul-ture of maize and cowpea, maize and tomato, cowpea and tomato, three seeds of each plant were sown. Two seeds of each plant were sown in the pots with the three crops. The treatments were then supplied with 500 mL of tap water in the morn-ing and in the evening respectively until the seedlings become fully established. The photosynthetic pigments were determ-ined spectrophotometrically with three replicates. Plant growth indices were determined according to Hunts (1978) using leaf area and dry matter data collected at four and six weeks after planting. Statistical analysis was performed using statist-ical analytical software SAS version 9.2. The results indicated that photosynthetic pigments accumulation (Chlorophyll a, b and carotenoid) in maize (15.98, 23.92 and 44.72 μM), Chlorophyll b and carotenoid in tomato plants (12.48 and 1,178.7μM) in the sole stands were more than the mixed culture of maize with cowpea and tomato (7.195, 14.74 and 0.00 μM). Also, total Chlorophyll in maize (1,127.8 μM), Chlorophyll a and total Chlorophyll in tomato (3.95 and 1,317.5 μM) in the mixed culture were more than in the sole culture of maize (1,030.9 μM) and tomato plants (?9.40 and 546.3 μM). The dif-ferent photosynthetic pigments accumulated in cowpea were greatly enhanced in the mixed culture than in the sole culture. All the photosynthetic pigments of maize, cowpea and tomato in all the treatments analysed in this study were signific-antly different atP>0.05. Plant growth indices such as net assimilation rate, relative growth rate, crop growth rate and tis-sue water contents of these plants had higher value in the intercropped than the check crop (sole). These plant growth in-dices were significantly different to one another atP>0.05. This study concluded that competition for shared resources in the mixed culture of tomato, maize and cowpea enhanced growth and accumulation of photosynthetic pigments.