DEFOLIATION AS A RESULT OF DECLINE IN THE ABSOLUTE PHOTIC RATION (SUMMER DEFOLIATION)
Abstract
Foliage leaves which are prevented from assimilating carbon dioxide die after varying lengths of time and in the case of woody plants separate as a rule from the trunk. This is the chief reason that leaves kept dark die after a longer or shorter time and separate from the trunk. Many deciduous trees shed their foliage in a few days when cut off from light, while the foliage of the laurel remains alive for many weeks under these conditions and does not separate from the trunk. Trees with foliage sensitive to shade generally undergo a partial defoliation during the summer which is attributable to the fact that the decline in daily light intensity following the beginning of summer brings about a reduction of the (absolute) photic ration of the plants concerned below the minimum, and this in turn brings about separation of the leaves. 'Summer defoliation,' that is the defoliation occurring in the summer in consequence of the decline in absolute photic ration, often takes from the trees up to 20% of their foliage, but sometimes less (8% has been observed) and sometimes more (up to 30% has been observed). Trees whose foliation extends into the summer, if they are sufficiently sensitive to shade, have leaf drop throughout the summer. The 'summer defoliation' described is not to be confused with 'heat defoliation, ' which sets in as a result of drought and heat.
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 23, 1966
- Accession Number
- AD0835289
Entities
People
- Julius Wiesner
Organizations
- United States Army Biological Warfare Laboratories