particular genes for transcription ( Kouzarides, 2007 ; Nelissen et al., 2007 ). Premature defoliation, i.e., before a normal killing frost, of the entire tree markedly reduces pistillate flowers the next year ( Hinrichs, 1962 ; Worley, 1979a ). Early
Early fall (September) defoliation and late spring (early June) shading of “off” and “on” pistachio trees were used to test two hypotheses: that 1) fall defoliation would reduce carbohydrate storage sufficiently to suppress spring growth and 2) spring shading would reduce carbohydrate status and increase inflorescence bud abscission. Defoliation suppressed initial leaf area expansion the following spring on current year shoots of “off” but not “on” trees respectively. Suppression of leaf size was correlated with the initial low concentration of carbohydrates in organs of individual branches of the tree. Fruiting and artificial shading in June had more dramatic effects on growth parameters than defoliating. Shading “off” trees for 14 days in early June accelerated abscission of inflorescence buds, reduced dry mass of individual leaves, buds, current year and 1-year-old shoots. Shading also reduced the concentration of total nonstructural carbohydrates (TNC) of these organs in “off” and “on” trees. Fruiting suppressed leaf size and leaf dry mass by 20% and 30% among individual branches of undefoliated and defoliated trees respectively. Low carbohydrate concentrations in individual branches and inflorescence buds following shading were closely correlated with the abscission of inflorescence buds.
; Harley et al., 1942 ), and may be a practice to manipulate biennial bearing because partial defoliation in off-years prevents excessive flower formation in on-years ( Davis, 1957 ; Fulford, 1960 ). In these studies, partial defoliation reduced but did
Abstract
Defoliation of transplants of tomato (Lycopersicon esculentum Mill.) at planting delayed plant development (including fruit maturity), but leaf areas of defoliated and nondefoliated plants were equal at fruit maturity. Defoliation at first bloom, full bloom, or 2.5-cm fruit diameter resulted in progressively less leaf area at harvest as the degree of defoliation increased. Defoliation of 80% at the above 3 stages of flower/fruit development resulted in reduced yield. Defoliation of 25% or 50% prior to or at full bloom had no apparent influence on yield. However, 25% or 50% defoliation when fruits were near 2.5-cm diameter resulted in yield reduction. Defoliation had no apparent influence on fruit size at harvest. Soluble solids in the fruit were reduced progressively with each successive increase in defoliation, while titratable acidity and pH were not affected. Defoliation increased photosynthesis in remaining leaves 4 and 14 days after treatment but had no effect on transpiration.
( Elsysy et al., 2019 ). Flower induction genes have been shown to be active in the leaves ( Hanke et al., 2007 ). Flower formation is affected by leaf area ( Sahulka, 1967 ), and defoliation decreased flower formation ( Elsysy and Hirst, 2017 ; Fulford
; Serrhini and Zeroual, 1995 ). Particularly, the disease has been described as a major problem in soils infested with highly virulent defoliating isolates of the pathogen in Andalucía (southern Spain) ( López-Escudero and Blanco-López, 2001 ), where more
/wet climates due to the potential for rapid defoliation of susceptible cultivars. Repeated defoliation events can weaken plants, leading to diminished aesthetics; in severe cases, they can contribute to plant death (e.g., winterkill). Outdoor-grown roses are
During production of florists’ hydrangea, defoliation before cold storage is required for prevention of diseases such as botrytis bud rot ( Bailey, 1989 ). Many hydrangea growers manually remove leaves before natural leaf abscission. This practice
can be observed. On the other hand, vigorous vegetative growth following a pruning or defoliation treatment is a common observation in citrus ( Eissenstat and Duncan, 1992 ; Phillips, 1978 ). Consequently, it is likely that the new growth emergence is
Summer-grown Hydrangea macrophylla subsp. macrophylla var. macrophylla (Thunb.) were exposed for 1 week to CzH4 at 0,0.5,2.0,5.0,50, or 500 μl·liter-1 in dark storage at 16C for defoliation before cold storage. The number of leaves remaining per shoot for all cultivars decreased with C2H4 concentration, and >5 μl C2H4/liter was effective in defoliating `Kasteln', `Mathilda Gutges', and `Todi' but not `Merritt's Supreme'.