Let me explain with the example of sugar, the movement of sugars in a plant is much different than the movement of water. First of all, phloem can move both up and down a plant, which comes in handy when a plant needs energy down below to grow new roots, or when a tasty apple is developing on a high branch. The sugars are made in the leaves as a product of photosynthesis. To get the food made in the leaves to other parts of the growing plant requires energy. So, with the help of some water from the xylem, sugars are actively loaded into the phloem where the sugars were made (which is called the source) and actively offload where they are needed (which is called the sink). In plants the movement of nutrients through the phloem is driven by where the sugar is most needed for the growth of the plant. Seeds are considered the poor sink of micronutrients in comparison to other parts of plants.

Iron and zinc are critical for hundreds of physiological processes in plants. In particular if the iron and zinc is deficient photosynthesis is hampered and chlorosis or yellowing occurs. The availability of iron and zinc are compromised particularly in alkaline soils. One of mechanisms plants have developed to survive and flourish is to concentrate zinc and iron in their seeds when they can. Before photosynthesis is self supporting the reserve iron and zinc can allow the metabolism to continue. Once an active photosynthesis is established the energetic resources from the sun can be transferred to the soil where root exudates can trigger a flourish of mycorrhizal fungi which can facilitate the delivery of water and nutrients from the soil to plant. The ability to concentrate critical immobile nutrients such as iron and zinc can be capital needed to set up this profound relationship.

Thanks for Your answers and precious time,

Dr. Paul, If you can please discuss briefly about the storage form of Zn and Fe in seed. Why plant localize more micronutrients in bonded form with organo phosphates (Phytic acid) and is there any possibility to manipulate This mechanism of storage with special reference to Zn Bioavailability in food?

One of the major problems is, as more farmers rely on artificial fertilizers, our fruits and vegetables contain less micro-nutrients. Providing seaweed, vegetable compost, and composted manure to the soil of growing plants, we measure and increase in all elements needed by the plant and plant consumers.

Phytic acid as Wikipedia describes is related to and helps regulate essential and vital cellar functions in plants animals and microbes. In fact the low phytate mutants are generally inviable.

Of the numerous properties which are positively associated with phytic acid is its association with anticancer and antioxidant properties.

As one study concludes “given the numerous health beneftis of phytates it participates in normal physiology and when phytate is deficient the impaired condition is reversed by providing sufficient phytate indeed phytate could be considered an essential nutrient like vitamins.

Using grains high in phytate by sprouting and fermentation releases zinc and iron that tends to be held with phytic acid. This strategy makes sense while the idea of creating low phytic acid mutants is questionable.

It is possible due to tightly network of low molecular weight ligands membrane transport, Zn -binding protein and as well as regulators

The critical zinc iron and phosphorus might be envisioned as a charged battery. The critical elements are stored especially in the aleurone layer and when germination conditions occur the enzymatic apparatus mobilizes the seed reserves and proteins like phytases are build up to mobilize them. As roots spread out and mycorrhizae are stimulated much of the continuing nutrition will come from the soil but the initial stages are dependent on the seed reserves.

Thank you Professor Happerly for your anwers and thank you dr Sarwar for this important topic.

Thanks Dr Paul and others for valuable discussion. Yes Dr. Paul I agree with your arguments, during seed germination, Phytate undergo hydrolysation and releases phosphate and micro-nutrients (like Zn and Fe) for seed germination and to support newly emerging seedling. Likewise a healthy practice in south Asia (in countrysides/ villages) is adopted to use sprouted wheat seeds based homemade products rich in Zn and Fe compared to normal wheat flour. It may also be beneficial to included sprouted wheat/ barley/ maize seeds in meat and milk providing animals to improve Zn and Fe status of milk and meat based human diet.

Dear Nadeem Sarwar,

Thank you for your kind comments.

In terms of phosphorus it is probably the most limiting nutritional element. Weathered soil has little of it.

Bacteria are particularly rich in phosphorus.

As such fermented foods are especially valuable. Soybean can have a lot of phytate locked phosphorus when the bean is fermented through Bacillus natto bacteria the phosphorus is unlocked and at the same time the zinc and iron is unleashed.

In terms of the soil mycorrhizae, soil bacteria and earthworms can be wonderful for releasing insoluble forms of phosphorus and stimulating better plant and animal production. Thank you for bring up this very important area of concern.

Some interesting responses have already accrued. Seeds are the strongest sink for nutrients , therefore , they are an avid accumulator of nutrients, regardless of mode of fertilization...

Dr Malhotra has beautifully described the sink-source relationship ..