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- Author or Editor: P. B. Catlin x
- Journal of the American Society for Horticultural Science x
Abstract
Individual plants varied considerably, but peach and apricot were more sensitive to waterlogging than was plum. No differences were established between peach and apricot. All 3 species became more sensitive as temperature was increased between 17 and 27°C. More than half of the plum seedlings survived at 17°C whereas all plants of the other 2 species died. A scion of a more tolerant species did not overcome the sensitivity of the roots.
Both cyanogenic glycoside content and the proportion of it that was hydrolyzed during waterlogging were higher in peach than in plum roots. Exposure of detached root systems of all 3 species to anaerobic conditions caused HCN to be released. The rate of cyanogenesis increased with both temperature and time. Peach and apricot roots were alike in HCN evolution whereas plum roots were lower, with release of HCN being barely detectable at 22°C. Cyanogenesis was significant in peach and apricot at as low as 17°C.
A close association exists among differential sensitivity, glycoside hydrolysis, and cyanogenesis in the absence of O2. However, the latter may be secondary, though contributory, to cellular disorganization as a cause of sensitivity.
Abstract
With normal pear leaves, soluble carbohydrates (sorbitol, sucrose, glucose, fructose) and starch were higher in green than in abscising, yellow senescent ones. Considerable accumulation of these components occurred in curl leaves which were about to abscise. Greatly reduced transport of photosynthetically fixed 14C from the leaves occurred in curl-affected trees. Normal leaves photosynthesized and exported C even when abscission was imminent as long as chlorophyll was present. Curl-affected leaves abscised earlier while considerable photosynthetic potential remained. As normal leaves approached senescence their N content decreased dramatically. Curl-affected leaves abscised when N levels were still high. Curl deprives the tree of potentially utilizable carbohydrate and N resources through inhibition of translocation and premature abscission. These effects of curl may explain reduced vigor and productivity as well as difficulties in establishing young trees. It is postulated that curl and decline are not solely graft union problems.
Abstract
Alternate bearing in the pistachio (Pistacia vera L.) is brought about by abscission of inflorescence buds during July and August when seed growth and development take place. There was rapid accumulation of sugars and conversion to fat in the nuts at that time, but sugar and starch levels in the bark and wood of nut-bearing branches were not appreciably different from those in similar tissues of non-bearing branches. The inflorescence bud-drop phenomenon does not appear the result of carbohydrate deficiency.
Abstract
Seedlings of Juglans hindsii Jeps. and J. regia L. reacted similarly and were much more sensitive to waterlogging at root temperatures of 33°C than those of Pterocarya stenoptera DC. At 23°C,J. regia expressed symptoms of waterlogging earlier than J. hindsii. Paradox plants, hybrids between the 2 walnut species, were more tolerant than J. hindsii but are still considered highly sensitive to anaerobiosis. These results support the contention that use of J. regia seedlings as rootstocks to avoid blackline introduces greater potential for damage if soils become saturated. Some plants of each type which demonstrated increased tolerance have been selected. Levels of abscisic acid, or changes therein did not appear to be useful parameters in screening walnut seedlings for tolerance to waterlogging. Phenolic compounds decreased in roots of waterlogged plants. Although the magnitude of change in phenols was the same in Juglans and Pterocarya plants, it occurred over a much longer period with the latter. Phenols lost from roots may be a secondary phenomenon but contribute to hypersensitivity of Juglans to waterlogging.