Phosphorus Deprivation Effects on Productivity, Photosynthesis and Car- bohydrates Accumulation in Hydroponically Grown Brassica Alboglabra Baileyat Different Growth Stages

Brassica alboglabra Bailey plants were first grown under full nutrient solution for 2, 3 and 4 weeks and then were transferred to phosphorus (P)-deprivation solution for 3 weeks (–P3), 2 weeks (–P2) and 1 week (–P1), respectively. The total growth duration was 5 weeks for all plants and the full P plants were grown under complete nutrient solution for 5 weeks. Full P and –P1 plants had similar productivity which was significantly higher than –P2 and –P3 plants. Pdeprivation treatments caused a reduction of the P concentration in all treated plants compared to full P plants. The total P content per plant was significantly higher in full P than any other P-deprivation plants. P-deprivation did not cause significant changes in chlorophyll (Chl) fluorescence Fv/Fm ratio and Chl content. There were no differences in light saturated photosynthetic CO2 assimilation (Asat) and stomatal conductance (gssat) in young leaves (YL) among all plants. However, P-deprivation resulted in reduction of gssat for old leaves (OL).Full P plants had the lowest soluble sugarsaccumulated inboth YL and OL compared to P-deprivation plants. There were no significant differences in the concentration of insoluble sugar of YL among all plants. The concentration of insoluble sugar in OL of full P and –P3 plants were significantly lower than in –P1 and –P2 plants. This study concludes that B. alboglabraBaileyplants are able to accumulate adequate P in its early growth stages and reserves of P are sufficient one week before harvest for quality crop yield. Relationships among productivity, photosynthesis and carbohydrate levels under P deprivation at different growth stage were discussed.