More Roots = More Fruits!

Soft Secrets
22 Jun 2012

Top end growth may well be your ultimate goal, but don't neglect the foundations on which your plants are built. Concentrate on developing a healthy root system and you'll achieve healthier growth and bigger yields.


First off, let’s all agree on one thing: the roots are the most important part of your plant, as they are responsible for delivering water and minerals. The amount of water and nutrient a plant uptakes is directly related to its rate of growth, and ultimately the size of the fruits it produces. Without a well-developed root zone, you are not going to achieve well-developed buds.

But roots just take care of themselves, right? Well, in most cases, yes – to an extent. But when roots are not given what they need they can become damaged, and this is where the problems start. A damaged root zone is vulnerable and nature will step in and attack. Diseases (or 'pathogens') will invade a root zone and, at best, slow down growth; at worst, they can ruin an entire crop.

So, how do you prevent attack? Firstly, provide roots with what they need. A well-draining, aerated root zone that is clean and kept at the right temperature (as close to 72° F/ 22° C as possible) will keep roots healthy and happy. One important fact that should motivate you to take care of the roots is that, when stressed, the roots will emit a hormone called ethylene; this hormone is recognized by some plant pathogens as a sign of weakness and a motivation to attack!

 

The Invaders (a.k.a. The Bad Guys): Root problems develop when pathogens attack the roots. Put simply, a pathogen is an organism that induces sickness in a plant. They live all around us (and in some cases on us) and remain harmless – as long as the plants are in good health. However as soon as your plants become damaged or stressed, they attack. Know your enemy... here is a quick explanation of two of the most common root zone pathogens:

Rhizoctonia

This soil borne fungus causes root rot and collar rot in seedlings and young plants. When a plant is infected, small white threads may be visible in the soil and reddish-brown spots may appear on the leaves and stem. When Rhizoctonia causes collar rot, a ring of fungus will develop on the stem, cutting off the supply of nutrients to the rest of the plant. When it infects the main stem of a seedling, the whole plant will die.

Rhizoctonia flourishes in wet and warm environments. If it is present, ensuring plants are not over-watered and that grow room temperatures are not too high can keep it suppressed (as will an early application of Trichoderma). If you do lose a crop to Rhizoctonia, ensure that you dispose of all of the soil in your grow room and remove all dead plant material before thoroughly scrubbing down and starting again.

Pythium

Of all the pathogens that attack plants, Pythium is the one that strikes fear into the heart of the home grower – particularly the home grower using bare-rooted, recirculating hydro systems, such as NFT or aeroponics. Pythium is better known as root rot or ‘damping off’. Its symptoms are easy to spot: the growth of the plant will become stunted, leaves will become yellow and eventually die, and the roots look brown, become ‘sludge-like’ and are easy to break off.

It is a spore that lives in air and water and it will be present in your growing area, no matter how clean it is. There are plenty of opportunities for it to enter your room. It will enter on your shoes, your clothes, your hands, etc. It will also come in with your water, especially when your water supply comes from wells, rivers or streams. It is therefore important to keep your growing environment clean – and make sure that you use clean water to feed your plants.

 

So if Pythium is everywhere around your plants anyway, why don’t all your crops go down from root rot? One thing to remember is that Pythium is a 'secondary infection': it will only attack your plants if they are already sick or damaged, or when growing conditions are not at their best. It takes advantage of sick or wounded tissues to colonize the root, causing damping off and root rot.

In nature, Pythium is often found in field soil, sand, pond or stream water, and dead roots of previous crops. It can sometimes be found in commercially available soil-less potting mixes and is easily introduced into a root zone by using dirty tools, dirty pots or generally poor hygiene in the grow room. It is also believed that fungus gnats and shore flies may be involved in moving Pythium from place to place.

Pythium can cause severe root rot because it has few competitors to check its activity. If Pythium infests a cutting bed, or if contaminated water is used in propagation, large losses occur. Root tips – very important in taking up nutrients and water – are attacked and killed first; Pythium spores then take over the root zone and can even spread up the main stem of an established plant.

How to Manage Pathogens: It may sound cliche, but when dealing with root zone pathogens prevention really is the best cure. Keep your plants healthy and they will be far less susceptible to attack:

Nature's Helpers (a.k.a. The Good Guys): So, you have scrubbed down the grow room, checked the health of your mother plants and have been extra careful not to damage the roots of young plants when transplanting – all important housekeeping factors in maintaining healthy plant roots. If you are looking for a little extra help, Mother Nature has some tricks up her sleeve, but they may seem a little strange. Say the word 'fungus' and what springs to mind? Moldy bathrooms and leftover food? (Put down that spliff and go clean your house!) While it is true that some types of fungus are undoubtedly a bad thing, Mother Nature sometimes lends a helping hand to home growers.

Mycorrhiza

The word 'mycorrhiza' literally means 'fungus root'. Mycorrhizal fungi invade the root zone of a plant to obtain nutrition. In doing so, these fungi assist the roots in uptake of minerals from the growing medium – the added nutrient uptake leads to faster development and quicker growth. When added to soil or cocos, the mycorrhizal fungi quickly establishes itself and forms a symbiotic relationship with the roots, breaking down elements and making them available for the plants (while feeding on the carbohydrates that the plant produces). Think of them as a root extension, increasing nutrient uptake and speed of development.

Mycorrhizal fungi increase the uptake of nutrients because the fungus forms a fine network of threadlike strands – called hyphae – that serve as an extension of the plant’s root system. There may be up to ten feet of hyphae growing out from each half-inch of root that is infected by mycorrhiza. The diameter of a fungal hypha can be one-fifth of the size of even the smallest root hair and may be many times longer, allowing it to explore areas of the growing media that the roots of the plant would not be able to reach on their own. By accessing the previously untapped nutrients in the growing media, the plant receives overall better nutrition and is more likely to reach its optimum potential (i.e., bigger yields).

Mycorrhizal fungi are especially beneficial in helping the plant access nutrients that are not particularly mobile in your growing medium, such as phosphorus and potassium – key elements required for packing on buds! Products containing mycorrhizal fungi can be purchased and applied to artificially introduce the fungi into soil or cocos. When applying these products, the hope is that the mycorrhizal fungi will not only increase plant growth and vigor, but will make them more tolerant to stresses, such as temperature fluctuation, over- or under-watering, and attack from root pathogens... stresses and issues familiar to every indoor gardener, new and experienced!

Trichoderma

Trichoderma are fungi that are present in nearly all soils and other diverse habitats. In natural soil, they are typically the most commonly occurring type of fungi. The majority of compost-based growing media available from your local grow shop will have Trichoderma present, and with good reason. Trichoderma is an aggressive fungus that will readily colonize the roots of the plant. The most competent strains can be added to growing media, or even to seeds, and are able to grow on roots as they develop. This is why many growers choose to dip their cuttings in Trichoderma, as the fungi will remain present on the roots of the plant throughout its life cycle (although it is a good idea to reapply every thirty days to keep numbers effective).

The strains of Trichoderma available at your local grow shop are known to control every pathogenic fungus for which control has been sought. They work on two levels: Trichoderma is a parasitic fungus that actively takes over a root zone and makes it difficult for damaging pathogens, such as Pythium and Rhizoctonia, to compete for space on the roots and for nutrients. Once established on the roots of a plant, Trichoderma will detect other organisms within the vicinity and grow towards them. The Trichoderma then coils itself around the organism and breaks down the cell walls by releasing enzymes, paralyzing the offending organism and rendering it inactive!

Once they come into contact with roots, Trichoderma will colonize the root surface and penetrate a few layers into the root itself, which actually induces plants to 'turn on' their natural defense mechanisms, making them stronger and less susceptible to attack. Compare this to when you have your vaccinations before going abroad – when your body is attacked it produces antibodies to fight the attacker, similar to what happens here. By fighting against the attacking Trichoderma, the plant bolsters its defenses, marking it harder for any pathogen to penetrate.

So, it’s mycorrhiza for faster development and increased growth rates, and Trichoderma for pathogen control and defense. But hang on, those of you paying attention may be thinking, I want the best of both worlds, but if Trichoderma is so aggressive, won’t it attack any mycorrhiza I add to the root zone? Many scientific studies have been carried out to monitor the effects of adding both fungi to the root zone and the consensus is that both perform separate jobs and can work in synergy, rather than canceling each other out.

Ultimately, the key point to remember is that the level of beneficial fungi activity in the root zone will reach a saturation point, depending upon the amount of food available for the fungi. So, keep conditions right, reapply your beneficial fungi at least once every thirty days, keep the root zone well fed, and let Mother Nature do her work. Happy growing!

S
Soft Secrets