Keeping the balance of leaf canopy to root mass crucial in achieving yield

Taking cucumber plants as an example to explain the advantages of keeping the balance of leaf canopy and root mass, the information in this editorial becomes apparent.

Cucumber roots have a high The combined effects of these changes draws energy from the plant that would oxygen requirement and are seen as stunted or wilted tops and normally be used for root development, sudden temporary wilt, root death; roots will often be at the thus reducing the root mass. Similarly, ‘epinasty’, of greenhouse surface of the media where oxygen loss of leaves in the lower extremities of cucumber plants is often noted. A high is available. In such circumstances, the plant are often evident, due to low solution temperature also reduces the balance of leaf canopy to roots is light or infection, yet growers allow fruit the amount of dissolved oxygen in the compromised. In addition, Pythium is an to develop on these nodes where leaf solution. Oxygen diffuses through air opportunistic fungus and often takes hold abscission is noted. 10 000 times the rate at which it diffuses of plants stressed by a combination of high These fruit have no “neighbouring” leaves through water, thus waterlogged soils and temperatures and low oxygen levels in the to supply the energy for the development media are undesirable. Oxygen content of root zone. of these fruit, and thus draw energy from a fully aerated solution at 10˚C is 13 ppm Bearing the above in mind, basics such as the plant that would usually be used by and at 30˚C it is 7ppm. media amelioration should be considered the root system, thus causing a decline in This may not seem significant but mandatory to further improve media the efficacy of the root system. at higher temperatures the oxygen properties and boost oxygen levels. Conversely, a poor canopy as result requirement increases as respiration Oxygen is part of the respiration process of poor nutrition, disease or climatic increases. Alcohol, hydrogen sulphide whereby carbohydrates are broken down conditions will have a reduced capacity and ethylene are produced in the roots in to provide energy for the plant, this being to produce energy required for fruit waterlogged soils and media and hormone the opposite process of photosynthesis. development and in turn having reduced production is also disturbed. Media such Products of respiration are carbon energy for root development and as sawdust often compact over time, dioxide as well as a wide range of carbon root exudates, further exacerbating which leads to water logging and results compounds exuded from the roots. the problem and diminishing the yield in low oxygen levels in the root zone and impaired potassium, phosphate, manganese and iron uptake. The ability of water to move into the roots is reduced almost threefold in the absence of oxygen in the root zone, mainly under Carbohydrate + O² ↔ CO² + H²O + energy Growers often avoid removing the lower fruit on cucumber plants in a bid to get quick yields, this load on the potential. In such cases growers should be able to “read” the plant and remove fruit to allow the plant to carry a suitable fruit load without compromising the root system or plant health. waterlogged conditions. plant at such early developmental stages By Mike Haupt