اثر فسفات و فسفيت در pH هاي مختلف بر عملكرد، رشد و وضعيت فسفر در كلم بروكلي

Effect of phosphite and phosphate in different pH on yield, growth and P status in Broccoli

فسفر يك عنصر ضروري است كه نقش‌هاي مهمي در متابوليسم‌هاي كربوهيدرات‌ها و سيستم انتقال انرژي ايفا مي‌كند. فسفيت ( -phi,PO33 ) يك شكل احياء شده فسفات (-pi,PO43 ) مي باشد. لذا به منظور بررسي اثر فسفات و و فسفيت درpH هاي مختلف بر عملكرد، رشد و وضعيت فسفر در كلم بروكلي آزمايشي به صورت فاكتوريل و در قالب طرح پايه كاملا تصادفي و با دو فاكتور شامل منبع فسفر ( در سه سطح فسفيت، فسفات و نسبت مساوي فسفيت فسفات) و pH ( در سه سطح 5.5، 7 و 5.8) و با چهار تكرار انجام شد. در پايان آزمايش، اثرات اصلي منبع فسفر و pH بر غلظت فسفر و پتاسيم برگ در سطح احتمال 1 درصد معني‌داربود، درضمن اثر متقابل منبع فسفرpH× بر فسفر برگ در سطح احتمال 1 درصد و بر پتاسيم برگ در سطح احتمال 5 درصد معني‌دار شدند. كمترين وزن تر هد(عملكرد) مربوط به تيمار فسفيت مي‌باشد و در واقع چنين مي‌توان نتيجه گرفت كه فسفيت استفاده شده به عنوان منبع فسفر باعث توليد هدهاي كوچك و نابالغ و حتي در بعضي از گياهان مانع توليد هد شد و باعث ايجاد حالت سميت و در نتيجه كاهش عملكرد را در پي داشت.

Introduction: Phosphorus (P) is an important nutrient for the plant affecting many physiological functions in plants. Phosphite (PO33; Phi; valence of +3), a reduced form of phosphate (PO43; Pi; valence of +5), that are being widely marketed either as an agricultural fungicide or as a superior source of plant phosphorus (P) nutrition. Furthermore, pH of both nutrient and soil solution alter the availability of P by the plants. There is insufficient information concerning the use of phosphite in plant. It could be possible to use of phosphite and phosphate to improve the P nutrition of plants. Materials and Methods: An experiment was conducted to investigate the effect of phosphite and phosphate in different pH on yield, growth and P status in broccoli (Brassica oleracea var. italicacv. Fiorentino). The experiment was conducted with three pH levels (5.5, 7, 8.5) factorially combined with three P source levels (Pi, Phi and Pi& Phi). The plants were grown in black buckets containing 8 L of aerated nutrient solution for 10 weeks. At the end of experiments the plant were harvested to measure the agronomical and physiological characteristics. The concentration of P was measured in the recently matured expanded leaves. Results and Discussion: Results indicated that the growth of broccoli plants was affected by the form of P. Phosphite significantly reduced the yield of plant. In Phosphite treated plants immature heads (button-like flower heads) was observed. Likewise, Phosphite increased phosphorus and potassium concentration in the leaves, roots, Stems and heads. Both P and K concentration were significantly reduced by the increase pH level. The highest yield was observed in Pi& Phi with pH (5.5) at 237 g plant -1 .Phosphate (pH=5.5) compare to Phosphite (pH=5.5) increased by 75% in yield. The increase in Pi uptake in the Phi treatment plant caused increased in P concentration in leaves and growth reduction and phytotoxicity. The negative effects application of only Phosphite was strong inhibiting effect in fresh weight head. Despit of increased P concentration in Phosphite treated plant, it seems that P from Phosphite source has no effect on P functional in plants. Conclusion: The findings this experiment indicted that Phosphite alone could not be used as a phosphorus fertilizer for the plants. however, the combination of Phosphite and phosphate improves the growth of broccoli plants