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Authors: Kaleem, Shuaib
Keywords: Applied Sciences
Agriculture & related technologies
Chemical engineering
Food technology
Issue Date: 2010
Publisher: Pir Mehr Ali Shah Arid Agriculture University Rawalpindi, Pakistan
Abstract: Sunflower (Helianthus annuus L.) having high degree of adaptability under wide range of climatic conditions, high photosynthetic capacity, efficient stomatal conductance and hydraulic mechanism allow the crop to be productive in broad range of environments. Combined effects of environmental factors not only modify plant phenology but also cause many physiological and qualitative changes. Environmental variations affect crop growth, development, yield, oil and fatty acid accumulation through agronomic, physiological and qualitative functions of the crop plant. Therefore, the present study was conducted to investigate and document the physio-morphic expressions of sunflower in response to varying environments. Field experiments were conducted at Agronomy Research Area, Pir Mehr Ali Shah, Arid Agriculture University, Rawalpindi, Pakistan one each in spring and autumn during 2007 and 2008. Four sunflower hybrids, Alisson-RM, Parasio-24, MG-2 and S- 278 were planted in randomized complete block design with four replications. Data for various agronomic, physiological and quality parameters were collected during the course of study. Results revealed statistically significant differences among hybrids for almost all parameter recorded during both the seasons (spring and autumn) during two years of study. Quantitative parameters like stem diameter, plant height, biological yield and achene yield of all hybrids were 26.14 % to 56.18 % higher in spring as compared to autumn season. Physio-morphic parameters like leaf area, leaf area index, specific leaf area, crop growth rate and net assimilation rate exhibited the similar trend of higher values during spring and lower during autumn but of sigmoid nature. Physiological attributes like chlorophyll content, stomatal conductance, transpiration rate, photosynthetic rate also followed the sigmoid curve pattern of growth and development during spring, where readings of all parameters were slow at the start of the season which gradually increased to the peak and thereafter decreased to the minimum at the end during spring season. However, trend of the above physiological parameters observed during autumn was opposite which touched the peak at the start and continuously decreased to the minimum at the end. The opposite trend of physiologicalxix parameters during two seasons may be related to the variable temperature during the two seasons. In spring, at the start temperature was low which gradually increased to the peak while during autumn temperature was relatively high at the start which gradually decreased as season proceeded. Qualitative parameters like oil content, oleic acid, stearic acid and palmatic acid of all the hybrids exhibited higher values during spring as compared to those during autumn season. However, linoleic acid showed inverse relationship with oleic acid as it increased during autumn than that observed during spring. Protein content showed opposite trend to oil content during the two seasons as higher protein contents were observed during autumn as compared to those during spring season. It may be concluded that spring crop is a better option for good economic and oil yield in high rainfall areas. However, autumn crop accumulated higher linoleic acid (poly-unsaturated fatty acid) than the spring crop, thus better in quality. Significant positive correlations were recorded among morphological attributes, achene yield and oleic acid, while negative for linoleic acid were observed during spring, however, during autumn oleic acid and linoleic acid showed opposite trend to each other. Similarly, significant positive correlations were exhibited among physiological attributes, achene yield and oleic acid, while negative for linoleic acid were expressed during spring, however, during autumn oleic acid and linoleic acid reversed each other. In a separate experiment, oil and fatty acid contents in different circles of mature sunflower heads during spring and autumn seasons for both the years were determined. A progressive decrease in oil content, oleic acid, stearic acid was recorded from outer to central circle during spring for both the years. Contrary to spring crop, oil content showed increase from outer to central circle in autumn crop. However, rest of the attributes followed the similar trend of spring crop. Linoleic acid accumulation was opposite to that of oleic acid where central circles accumulated higher linoleic acid in all four hybrids as compared to middle and outer circles during both the seasons. The variation in oil and fatty acid in different circles may be the result of vascular connection which seems to be better in outer circles.
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