EFFECTS OF NITROGEN FORMS ON THE GROWTH AND POLYAMINE CONTENTS IN DEVELOPING SEEDS OF VEGETABLE SOYBEAN

A pot culture experiment of nitrogen forms [nitrate (NO^? ₃ ): ammonium (NH ⁺ ₄ )] with four ratios (100:0, 75:25, 50:50, and 25:75) in nutrient solutions was conducted to examine the effect of nitrogen forms on the growth and polyamine contents of developing seeds of vegetable soybean [Glycine max (L.) Merr. cv. ‘Li-xiang 95-1′]. Results showed that the best plant growth vigor was observed in (75%), and then in (50%). However, the fresh and dry weight of biomass decreased when a high concentration of either (100%) or (75%) was the primary nitrogen source in the nutrient solution. The numbers of flowers and pods in (75%) were significantly decreased compared with other ammonium-nitrate ratios in which the numbers of flowers and pods were not influenced by nitrogen forms. During the development of seeds, levels of free Put and Spd decreased, and the decrease extents were more marked in 100:0 and 25:75 (:), but the change of free Spm was opposite. Levels of conjugated and bound polyamines in all nitrogen forms increased, but the increases in 75:25 and 50:50 (:) were not so obvious as in 100:0 and 25:75 (:) treatments. The possible roles of polyamines in the adaptive mechanism of vegetable soybean seeds to different nitrogen forms were discussed.     

Uptake and partitioning of 32P and 65Zn by white clover as affected by eleven isolates of mycorrhizal fungi

We compared the effect of eleven mycorrhizal fungi populations (Glomus spp.) from two different climatic regions (Iran vs. Switzerland) on the uptake and partitioning of ³²P and ⁶⁵Zn by white clover (Trifolium repens L. var. Milkanova). Fungi significantly differed in the colonization of roots with hyphae, vesicles or arbuscules and in their effect on the uptake of ³²P or ⁶⁵Zn by white clover. Fungi also differed in their effects on the percentages of ³²P or ⁶⁵Zn transported to the plant tops. There was no relationship between the uptake of ³²P and that of ⁶⁵Zn in plants colonized by different fungi. Isolates Z7 and Q12 (from Iran) were superior to Swiss isolates for their effect on the uptake of zinc (Zn) by white clover. Among the Swiss isolates, that from Langwiese and Hausweid resulted in the highest and lowest partitioning of both ³²P and ⁶⁵Zn to the plant tops, respectively. We conclude that the effectiveness of vesicular arbuscular mycorrhizae in uptake of phosphorus (P) and Zn may be nutrient specific and that some fungal isolates may also affect the relative partitioning of P and Zn between plant roots and tops.