Video No. 6 | The Function of Low pH in Foliar

What Science Says About


About this Series

An engaging series of 11 videos that feature Dr Hooshang Nassery and Carol Phillips in a conversational style presentation about the science that underpins RLF product and practice.

It has been called ON SOLID GROUND for good reason, because the science of plant physiology provides the indisputable basis upon which all RLF products are developed.

This series will bring a relaxed and simple understanding for farmers and growers everywhere about the science that underpins the RLF brand, and the expertise that goes into every specialised crop nutrition product that RLF manufactures.

Carol Phillips talks with Dr Hooshang Nassery about The Function of Low pH in Foliar

Carol Phillips (CP) : Can you explain now Hooshang, why low pH is important for Foliar products?

Dr Hooshang Nassery (HN) : Well, there are two aspects to low pH product to be superior to any high pH or alkaline pH. One, is that the hydrogen ion, which is abundant in a low pH product, will practically bind with the negative charges of the cell wall. And if you look at the plant structure, or cell wall structure, you would see that nutrients that are applied to the leaf, or for that matter come from the root into leaf free space, need to pass that free space in order to move around and get finally into the cell. The negative charges practically come from products of cell wall structure, which is referred to as polysaccharide galacturonic acid, and so on. So there are acid residues with negative charge, and they start to bind with those cations. Therefore, if I’m applying zinc, and rather than zinc going quickly into the cell (it) will be spent to neutralise those charges. Whereas, if I have an acid pH, or acid foliar product, it will neutralise those negative charges – in other words forget about those interferences of charge and fixation of those elements in the free space. Free space is outside the cell. And therefore, the entry into the cell will be very quickly achieved.

CP : So it’s important for rapid uptake of nutrients. Is it?
HN : That is right. Yes. It’s important for rapid uptake into actual cell – passing plasma membrane. Now the other side of it (benefits) of low pH, is that hydrogen ion is actually a proton bound with sucrose, sugars, starch saccharides – and then moves into the phloem tissue. Now, that naturally happens by expenditure of energy from the leaf cells – that they extrude hydrogen ion, and then they take the sucrose and hydrogen ion together. So, if I’m applying hydrogen ion in the fertiliser, I’m helping the energy-saving in the plant, and assisting with more sugar loading into the phloem. Of course, if I load more sugar into the phloem, then photosynthesis goes at a greater pace, and more nutrients, or more carbohydrates if you like, get into the other organs, including the root system.
CP : So, any product that is based around the technology of low pH is really a superior product, or superior crop nutrition product for the plant?
HN : For the foliar space.
CP : For the foliar.
HN : Now the reason is, that the root has got a different system. Root actually works best in a pH of, let’s say around 5. Now leaf tissue can benefit from that low pH, whereas low pH in the root system can damage the cell membrane. The low pH in the leaf free space creates a potential for sucrose uptake so the hydrogen ion is quickly consumed. Whereas, if I put a root system in a low pH, the low pH actually stops certain reactions like proton extrusion, which is needed to take the cations. In the leaf system, we continuously consume that low pH to make more sugar for plant.
CP : So how do you keep that balance? How does that balance between the root system and the leaf system of nutrient intake? How’s that created?
HN : Yes. Well, the balance is really, if we look at the mineral nutrition, stepwise, from the root to the leaf free space and inside the leaf, we really pass through four steps. So it’s not as simple as that, to keep the balance with the pH. We are trying to have the optimum pH for the root and we’re trying to have the low pH to benefit photosynthesis in the leaf. And the reason that we can’t do it through the soil – and that’s one reason we go for Integrated Fertiliser – because I cannot maintain low pH gradient in the leaf through the activity of the root system, because what comes up from the root system is normal pH (it’s about pH-5/pH-6), just like soil solution under most conditions. So the application to the leaf of a low pH foliar is our opportunity to induce photosynthesis, to increase photosynthesis.
CP : Very complex. Thank you for explaining that.
About Dr Hooshang

Hooshang is RLF's Plant Physiologist and he heads the company's Research, Development and Technical team. He brings the knowledge and enthusiasm for the industry with over 40 years of experience and he has played a central role in a number of new product developments, including the world-leading and innovative seed nutrition technology BSN. Contact Hooshang.

About Carol

Carol is RLF's Communications, Media and Policy consultant. She is the main author of information, marketing and website publications and part of her role is to plan targeted marketing and information strategies and resources for both customers and the wider RLF team. Contact Carol.

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