Effect of boron deficiency on vegetative growth, flowering and seed yield in oilseed rape plants (Brassica napus)

Boron is an essential micronutrient for plants and boron deficiency is a common nutritional disorder in crop species. In this research work, the effect of boron deficiency on the amount of pigments, phenols, soluble sugars, starch, chlorophyll fluorescence parameters and enzyme activity in oilseed rape (Brassica napus L. cv. RGS) plants during vegetative and reproductive period were studied. Boron deficiency caused reduction of plants dry matter production and impaired development of the young leaves. The leaf concentrations of chlorophyll, carotenoids and anthocyanin were decreased and the net assimilation rate was diminished following reduction of stomatal conductance and consequently, non-structural carbohydrates were decreased in the leaves of boron-deficient plants. In contrast, the leaf concentration of cytosolic phenolics compounds increased in boron-deficient plants associated with a rise in the leaf activity of phenylalanine ammonia lyase while polyphenol oxidase was not influenced by boron deficiency. Boron-deficient plants formed distorted inflorescences with higher rate of flower drop. Pollen tube showed apical swelling with lower germination percentage in boron-deficient plants. During the anther development, differentiation of the layers of pollen sac wall impaired by boron deficiency accompanied by an earlier disintegration of the nutritive cell layer. Boron-deficient plants had less fruits with lower growth rates and smaller seeds. Our results demonstrated that during vegetative growth, boron deficiency influences mainly carbon metabolism but during reproductive growth it affects several developmental processes including germination of pollen grains, development of the siliques and filling of the seeds.