color ( Yoshiaki et al., 2010 ). Several growers say that the loss of red color of G. bicolor in midsummer is less in leaves from shaded locations than in those in sun-exposed locations. Many studies have reported on the effects of shading on the
Nobuyuki Fukuoka, Takamoto Suzuki, Keisuke Minamide, and Tatsuro Hamada
Masafumi Johkan, Genjirou Mori, Kazuhiko Mitsukuri, Keiichirou Mishiba, Toshinobu Morikawa, and Masayuki Oda
cultivars that have lower shoot regeneration. Phenolic compounds are secondary metabolites in plant tissue and their biosynthesis is greatly influenced by light ( Crippen and Morrison, 1986 ). For instance, field shading of mango decreased the
Martin F. Quigley and Stephen Mulhall
Goldenseal (Hydrastis canadensis) is an herbaceous perennial valued for its fleshy rhizomes, which contain the alkaloids hydrastine and berberine. While it is understood that relative shade influences growth and yield of goldenseal, optimal shade level for maximum rhizome mass and plant vigor under cultivation has not been established. Goldenseal plants grown from cold stratified rhizomes were kept under shade for 5 months in the greenhouse. Treatments were five different shade levels ranging from 60% to 95% of full shade, plus a control group in full sun. Measured variables included rootlet length, bud development, and rhizome mass. Plants grown under moderate shade (60 to 70%) produced longer and more numerous rootlets, more bud primordia, and had greater rhizome mass and healthier leaves than plants grown under extreme shade (95%) or in full sun. Decreasing shade density had a major impact on plant condition and growth. Those plants grown with the greatest sun exposure displayed 100% scorch damage to the foliage, in comparison to <35% damage in the moderate shade (30 to 40%). The results suggest that moderate shading may double yield in rhizome mass, and promote increased bud proliferation in subsequent seasons. Late season leaf vigor is not correlated with rhizome mass.
Md. Shahidul Islam, M. Jalaluddin, James O. Garner, M. Yoshimoto, and O. Yamakawa
Sweetpotato leaves contain biologically active anthocyanins that have significant medicinal value for certain human diseases and may also be used as natural food colorants. Foliar anthocyanins and their relative abundance were investigated in leaves of sweetpotato cultivars `Shimon-1', `Kyushu-119', and `Elegant Summer' grown under artificial shading and different temperature conditions. High-performance liquid chromatography profiles of the cultivars tested showed similar peaks but with peak areas differing with cultivar, temperature and shading. The relative quantity of individual anthocyanin was YGM (Yamagawamurashaki)-1a> YGM-4b> YGM-1b> YGM-5a> YGM-0d> YGM-0a> YGM-2> YGM-0c> YGM-3> YGM-6> YGM-5b> YGM-0b> YGM-0f> YGM-0e> YGM-0g. Seven were peonidin and eight cyanidin derivatives. The highest anthocyanin contents were found in plants grown at a moderate temperature (20 °C) with lower levels at 25 and 30 °C. The leaves of plants grown in full sun accumulated significantly more total as well as the major individual anthocyanins than plants grown in 40% and 80% shade. The results indicate that growing sweetpotatoes at moderate temperatures and without shading facilitates the accumulation of anthocyanins in the leaves. The anthocyanin composition of the leaves is discussed relative to their physiological function in human health.
Muntubani D.S. Nzima, George C. Martin, and Chic Nishijima
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.
Kamal Aberkani, Xiuming Hao, Damien de Halleux, Martine Dorais, Stephen Vineberg, and André Gosselin
fogging systems have been used to prevent plant heat stress during the day. In fact, shading is one of the conventional and familiar techniques used by growers to decrease solar radiation and reduce air and leaf temperatures ( Sandri et al., 2003 ). Many
Evagelini Kitta, Nikolaos Katsoulas, Anna Kandila, Maria M. González-Real, and Alain Baille
low air relative humidity during a great part of the crop cycle ( Aloni et al., 1990 ; Dinar and Rudich, 1985 ; Erickson and Markhart, 2001 ). An alternative to alleviate the effects of radiation load is the use of reflection or shading (whitening
Madhumita Dash, Lisa K. Johnson, and Anish Malladi
Shading during early apple fruit development decreases fruit growth and induces fruit abscission and has been used to understand processes that affect thinning ( Byers et al., 1985 , 1990a , 1990b , 1991 ). During early fruit development, active
Kazuya Koyama and Nami Goto-Yamamoto
; Nagata et al., 2003 ). Bunch exposure or shading is regarded as one of the most influential practices because increased or decreased light exposure particularly on fruit bunches significantly influences the accumulation of anthocyanins and the total
Domenica Scuderi, Francesco Giuffrida, Stefania Toscano, and Daniela Romano
characteristics (e.g., a large surface area and dark green color of the leaves) and acclimatization to low light environments, such shading conditions limit the daily production of matter ( Cannell et al., 1987 ), and thus the production period is extended