A study was conducted to estimate heritability of the content of Mn, Fe, and certain other mineral elements which have been associated with leaf chlorosis and to determine the genetic relationships among shoot dry weight, visual rating, and the mineral elements in rabbiteye blueberry (Vaccinium ashei Reade). Plants from a 10-parent dialled set of crosses were grown in sand culture to which 200 ml of 250 ppm Mn solution were applied five days per week. Visual ratings (1 – dead plant - 13 – no toxicity symptom) were made after six weeks and shoot weight and mineral element contents were determined after 10 weeks of treatment. Heritability estimates were high for all variables except Fe, suggesting that change in Mn, Zn, Ca, Mg, or K content could be expected from phenotypic recurrent selection. However, manipulation of mineral content probably would not ameliorate the Fe chlorosis. The high heritability of shoot dry weight and visual rating and the high genetic correlation between the two variables suggest that plants resistant to mineral effects on Fe metabolism can be selected on the basis of visual rating.
Severely chlorotic ‘Red Delicious’ apple (Malus domestica Borkh.) trees growing on a calcareous soil were treated for iron (Fe) chlorosis with pressure injections of 1.0% (w:w) solutions of ferrous sulfate, ferric citrate, or Fe-Sequestrene-330 (Fe-330). Injections were made in September of 1981 and in April, June, and July of 1983. All treatments increased chlorophyll concentrations compared to controls, and treatments made in September of 1981 and in April and June of 1983 increased shoot growth during the 1983 growing season compared to controls. Although the treatments did result in a temporary increase in foliar Fe content, there was not a strong correlation between foliar Fe and chlorophyll concentration. Ferrous sulfate and Fe-330 were more effective than ferric citrate in alleviating chlorosis. Injections made in April and June of 1983 greatly increased bloom in May of 1984, compared to trees injected in July of 1983 and the untreated controls. Hence, injections should be made early in the season (before July) in order to promote bloom the following growing season.
Several experiments were conducted to find effective ways of utilizing gibberellin4+7 (GA4+7) and benzyladenine (BA) to prevent leaf chlorosis during greenhouse production of Easter lilies (Lilium longiflorum Thunb.) while minimizing the undesirable side effects on stem elongation. On an absolute concentration basis, GA4+7 was much more effective than BA in preventing leaf chlorosis. Excessive levels of GA4+7, however, tended to cause stem elongation. When applied at around the visible bud stage, if the foliage was well covered with the spray solution, 25 mg·L-1 of GA4+7 was adequate for maximum protection against leaf chlorosis. Increasing the GA4+7 concentration above 25 mg·L-1 gave no additional benefit on leaf chlorosis. Two possible modes of GA4+7 uptake during a foliar spray application (absorption through leaves and stems, and root uptake of the extra run-off) were studied in terms of their relative contribution to leaf chlorosis and stem elongation. Although both modes of uptake prevented leaf chlorosis, foliar uptake was much more effective than root uptake. However, GA4+7 taken up by the roots contributed mainly to stem elongation. When sprayed to leaves on only the lower half of the plant, a 10-mL spray of either 25 or 50 mg·L-1 of each GA4+7 and BA was enough for complete protection against leaf chlorosis. Increasing volumes had no additional benefit on leaf chlorosis, but increased the chances of unwanted stem elongation.
Iron deficiency chlorosis of ‘Washington Navel’ orange [Citrus sinensis (L.) Osbeck] on Poncirus trifoliata (L.) Raf. rootstock grown on Beth Guvrin calcareous soil was prevented when a combination of peat and FeSO4 was applied to a small portion of the root zone. Comparison of treated and control trees revealed a significant prevention of chlorosis and an increase in chlorophyll and peroxidase enzyme activity.
Iron deficiency chlorosis is a serious problem when many of a number of woody and herbaceous ornamental and fruit plants are grown on calcareous soils. Soil amendments, such as the various iron chelates, have been used with varying success (1,2,3,4), however, except for foliar application on citrus, chelates have found limited use because of their high cost and erratic or less than satisfactory results. The simple inheritance of chlorosis resistance in soybeans is well known (5), however, the few attempts to select chlorosis resistant fruit trees have been rather unsuccessful (6,7). Trees frequently will show no signs of chlorosis until the rcot system penetrates highly calcareous subsoil layers. Thus attempts to select for chlorosis resistance have given erratic year to year results and have, in general, been unsuccessful even after several years of testing.
Chlorotic `Manzanillo' olive (Olea europaea L.) trees and `Maycrest' peach [Prunus persica (L.) Batsch] trees were injected with Fe solutions using an apparatus that consisted of a plastic injector and a pressurized latex tube containing the solution to be injected. Injections were made on various dates from Sept. 1987 to July 1988. All treatments increased chlorophyll content compared to that of the control. Ferrous sulfate was the most effective Fe compound in alleviating chlorosis; its effect lasted for two seasons in peach and for at least three seasons in olive. Also, ferrous sulfate increased vegetative growth and affected cropping the year following injections. Ferrous sulfate at 0.5% to 1% is recommended to reduce the risk of foliar burning. The injection method effectively introduced Fe compounds into olive and peach trees.
Tomato plants (Lycopersicon esculentum Mill. cv. Bonny Best) grown in sand culture and provided with a complete nutrient solution or solutions containing sub- or supraoptimal Mg concentrations were fumigated with hydrogen fluoride (HF) at 5.0 or 9.7 μg F/m3 for 7 days. The severity of HF-induced chlorosis on apical and medial leaves was enhanced in Mg-deficient plants and suppressed in plants grown at the highest level of Mg. Foliar accumulation of fluoride (F) from exposure to the highest HF concentration was inhibited in plants provided the lowest and highest Mg levels. The presence of necrotic tissue probably suppressed the accumulation of F in Mg-deficient plants; however, it was not a factor in plants given supraoptimal Mg. The interactive effects of HF and Mg on foliar injury and F accumulation revealed that Mg-deficient plants were more susceptible and plants given excess Mg were more tolerant to HF than plants cultured on complete nutrient medium.
The influence of ambient UV radiation on growth, chlorosis, and flavonoid content was examined in four cultivars of cucumber (`Ashley', `Poinsett', `Marketmore', and `Salad Bush'). Plants were grown from seed in UV exclusion chambers consisting of UV transmitting plexiglass (10% T, 285 nm), lined with 3- or 5-mil Llumar (10% T, 399 or 404 nm) to exclude UV-A and UV-B, 5-mil polyester (10%T, 319 nm) to exclude UVB, or cellulose acetate (10% T, 291 nm) to transmit UV-A and UV-B. Plants were grown in 15 cm plastic pots containing vermiculite and were fertilized daily with nutrient solution. Despite their differential sensitivity to supplemental UV-B radiation, all four cultivars responded similarly to the exclusion treatments. After 19 to 21 days, plants grown under ambient UV-A and UV-B generally had less stem, leaf, and root biomass and less total height and total leaf area than those grown under conditions in which UV-A and UV-B or only UV-B was excluded. Flavonoid content, leaf number, and floral development were unaffected by UV. These findings demonstrate the extreme sensitivity of cucumber to current levels of solar UV radiation.
The interactions of ancymidol drenches, postgreenhouse cold storage, and hormone sprays on postharvest leaf chlorosis and flower longevity of `Nellie White' Easter lilies (Lilium longiflorum Thunb.) were investigated. Ancymidol drenches (0.5 mg/plant twice) during early growth resulted in leaf chlorosis in the greenhouse which intensified further during postharvest. Cold storage (4 °C) of puffy bud stage plants for 2 weeks also accelerated leaf chlorosis. The combination of ancymidol treatment with cold storage resulted in the most severe leaf chlorosis. Promalin (GA4+7 and BA each at 100 mg·L-1) sprays completely prevented postharvest leaf chlorosis, whereas ProGibb (GA3 at 1000 mg·L-1) was ineffective. Cold storage reduced flower longevity and increased bud abortion, however, the degree of bud abortion varied among experiments in different years. Both ProGibb and Promalin sprays increased flower longevity. Compared to positive DIF (difference between day and night temperature) grown plants, forcing under negative DIF (-8 °C) increased the severity of postharvest leaf chlorosis. Leaves were sampled from basal, middle, and upper sections of the stem after 4 and 12 days in a postharvest evaluation room, and analyzed for soluble carbohydrates and N. Total leaf soluble carbohydrates and N concentrations were less in basal and middle sections of negative DIF-grown plants than in positive DIF-grown plants. Leaf chlorosis was associated with depletion of soluble carbohydrates and N in the leaves. Chemical names used: α-cyclopropyl-α-(p-methoxyphenyl)-5-pyrimidinemethanol (ancymidol); gibberellic acid (GA3); gibberellins A4A7 (GA4+7); N-(phenylmethyl)-1H-purine 6-amine (benzyladenine).
The effects of Promalin® [PROM; 100 mg·L–1 each of GA4+7 and benzyladenine (BA)] sprays on leaf chlorosis and plant height during greenhouse production of ancymidol-treated (two 0.5-mg drenches per plant) Easter lilies (Lilium longiflorum Thunb. `Nellie White') were investigated. Spraying with PROM at early stages of growth [36 or 55 days after planting (DAP)] completely prevented leaf chlorosis until the puffy bud stage, and plants developed less severe postharvest leaf chlorosis after cold storage at 4 °C for 2 weeks. When PROM was sprayed on plants in which leaf chlorosis had already begun (80 DAP), further leaf chlorosis was prevented during the remaining greenhouse phase and during the postharvest phase. PROM caused significant stem elongation (23% to 52% taller than controls) when applied 36 or 55 DAP, but not when applied at 80 DAP or later. The development of flower buds was not affected by PROM treatments. Although PROM sprays applied at 55 DAP or later increased postharvest flower longevity, earlier applications did not. Chemical names used: N-(phenylmethyl)-1H-purine 6-amine (benzyladenine, BA); α-cyclopropyl-α-(p-methoxyphenyl)-5-pyrimidinemethanol (ancymidol).