3. CONTROL OF PLANT GROWTH AND DEVELOPMENT BY THE ROOT ENVIRONMENT - ROOT GROWTH AND ITS ENVIRONMENT
A short survey is given of various methods for root growth studies such as: water or gravel cultures, containers with a glass wall, the excavation of roots, the use of isotopes and the calculation of root resistances.
Root growth depends of the supply of assimilates from the shoot and on the carbohydrate storage. Defoliation, light intensity and carbon dioxide content of the air may influence root growth via photosynthesis. The transport of assimilates towards the root and the presence or absence of reproductive organs may also determine growth of the roots Some consequences of pruning have been discussed.
The shoot/root ratio depends on the species, the stage of development and certain climate and soil conditions. At a high shoot/root ratio plants may be more susceptible to water shortage and salinity.
The effect of soil factors such as mechanical resistance, water availability, temperature and soil aeration on root growth have been discussed.