Tolerance to alkalinity was evaluated in Rose `Pink Cupido', Vinca `Apricot Delight', Chrysanthemum `Miramar', and Hibiscus `Bimini Breeze' and `Mango Breeze'. Plants were potted in a sphagnum peat moss-based growing medium and irrigated with water containing 0, 2.5, 5, 7.5 and 10 mm of Na bicarbonate. In rose, shoot mass was significantly decreased and chlorosis increased at the 5 mm treatment, indicating that the alkalinity toxicity is between 2.5 and 5 mm. In chrysanthemum, the concentration of Na bicarbonate did not significantly affect shoot mass, but caused a significant increase in leaf chlorosis at 5 mm or higher Na bicarbonate. This indicates an alkalinity toxicity level between 2.5 and 5 mm. In Vinca, shoot dry mass was not affected significantly, but leaf chlorosis was significantly increased with 5 mm of Na bicarbonate. This indicates an alkalinity toxicity level between 2.5 and 5 mm. In hibiscus `Mango Breeze', shoot mass was significantly increased at 2.5 and 5 mm, but was significantly decreased at 7.5 mm and above. Leaf chlorosis was significantly increased with a concentration of 5 mm and above, indicating that in hibiscus `Mango Breeze' the alkalinity toxicity level is between 5 to 7.5 mm. In hibiscus `Bimini Breeze', shoot mass was not significantly reduced, but leaf chlorosis exhibited a significant decrease at 7.5 mm. this indicates that in hibiscus `Bimini Breeze' the alkalinity toxicity level is between 7.5 and 10 mm. Growing medium pH increased with increasing levels of Na bicarbonate. The species showed varying capacity for acidification of the growing medium. All species, except rose and vinca, neutralized the alkalinity effect of 2.5 mm, but none of the species neutralized the effect of 5 mm and higher Na bicarbonate.
of heat stress, including wilting, reduced plant and fruit size, small fruit number, and a leaf chlorosis. Poor plant growth in poorly ventilated high tunnels, under tropical conditions, has already been reported ( Rault, 1988 ). Fig. 1. High tunnel
. Cultures developed chlorosis and had less vigor, and multiplication rates declined. Commercial hemp producers conducting tissue culture tests have also experienced declines in shoot quality as cultures age during the short term. The observed decline of
in both ‘Dutch Master’ and ‘Ice Follies’. The leaves of most plants also maintained pigmentation without chlorosis or loss of chlorophyll, which is another key to maintaining visual quality and therefore suitability for landscapes or as potted plants
Iron-deficiency symptoms are observed on some genotypes of potato (Solanum tuberosum L.) grown on high-pH and calcareous soils. seven potato cultivars differing in response to iron deficiency chlorosis (FeDC) were grown on high-pH (8.1), calcareous (38% calcium carbonate equivalent in surface 20 cm) and silty clay soil in the field (Beka'a Valley, Lebanon), to determine the effects of FeDC on tuber yield of cultivars sprayed with Fe. A significant interactions between cultivars and Fe spray treatment were noted for visual FeDC ratings and tuber yield. Even though only slight FeDC was noted on some cultivars receiving no Fe spray, tuber yields were significantly increased when sprayed with Fe. Some cultivars with moderate FeDC ratings did not show a significant increase in yield when sprayed with Fe while other cultivars did. Sprayed cultivars generally produced higher tube; yields than unsprayed ones. Indicating that Fe-deficiency chlorosis in the Mediterranean region may be a serious limitation to potato tuber yield.
Potted Rosa × hybrida `Meijikatar' plants were produced at 350, 700, and 1050 μl·liter-1 CO2. At a stage of development where half of the flowers showed color, plants were placed into simulated shipping incubators for 5 days at 4 or 16 C.
Increased CO2 levels resulted in shorter production time, increased root dry weight, increased plant height, and reduced total chlorophyll in the upper leaves of the plants. Upon removal from simulated shipping, the number of etiolated shoots per plant increased with increased CO2 concentration. After 5 days in a simulated interior environment, higher shipping temperatures induced more leaf chlorosis, but there were no differences in leaf chlorosis due to CO2 enrichment.
In a sand culture study, increasing Na levels increased leaf concentration of Na, Mg, Ca, Mn, and Zn, and reduced leaf K and plant dry weight. Magnesium fertilization did not affect leaf concentration of Ca, K, Mn, Fe, or Zn. High Ca fertilization increased leaf Ca. At high Mg levels, Ca fertilization had a synergistic influence on Mg uptake. Ca and Mg fertilization did not independently influence plant vigor, chlorosis symptoms, or dry weight production of leaves and stems. As levels of Na fertilization increased, plant vigor and leaf production decreased and chlorosis symptoms increased. With low Na fertilization levels, high Mg fertilization reduced leaf production but with high Na fertilization, plants receiving high Mg levels produced twice the weight of leaves as those with low Mg fertilization. High Mg fertilization reduced the detrimental effects of high Na fertilization on plant growth. This effect may be due to the antagonistic influence of Mg fertilization on Na uptake at high Na fertilization levels.
Xylella fastidiosa is a fastidious gram-negative, xylem-limited leafhopper-transmitted bacterium that has proven to be the causal agent of many economically important horticultural plant diseases, including Pierce's disease of grapevine and citrus variegated chlorosis. Genetic relationships among 11 X. fastidiosa strains isolated from mulberry, almond, ragweed, grape, plum, elm, and citrus were determined using randomized amplified polymorphic DNA (RAPD). Twenty-two 10-base primers amplified a total of 77 discrete polymorphic bands. Phenetic analysis based on a similarity matrix corresponded well with previous reports on RFLP-based similarity relationships, indicating that RAPD-PCR amplification products can be used as a reliable indicator of genetic distance in X. fastidiosa. RAPD products have been cloned and sequenced, and pairs of 21-nucleotide PCR primers have been developed that detect X. fastidiosa in general and the causal agent of citrus variegated chlorosis specifically.
Foliar chlorosis or bleaching, interveinal chlorosis, leaf edge and tip necrosis, a poor root system, and stunted growth of Eustoma grandiflorum (Raf) Shinn seedlings were associated with a medium pH of 5.0 or 5.5 but not when the values ranged from 6.4 to 7.5. The range in medium pH resulting in the best growth of seedings and flowering plants was 6.3 to 6.7. Responses to medium pH were similar, regardless of fertilizer solution pH or cultivar. Eustoma seedling and shoot fresh weights for pH 5.0 and 5.5 were only 23% to 66% of corresponding values for plants grown at pH 6.4. Leaf tissue Zn was extremely high (1050 mg·kg-l dry leaf tissue) at a medium pH of 5.0, but other macro- and micronutrients in leaves were not at abnormal levels.
Eight species of low-growing woody and herbaceous landscape plants were evaluated for tolerance to 1.1 or 2.2 kg a.i. bentazon/ha (plus a crop oil) applied over the top twice 7 days apart. Raphiolepis indica L. Lindl. `Alba' was the only species tolerant to bentazon in either of two experiments. Bentazon injury to Liriope muscari (Decne.) L.H. Bailey `Evergreen Giant' was minor (slight chlorosis) and would probably be tolerable under most landscape situations. Injury (primarily chlorosis/necrosis) to Carissa macrocarpa `Emerald Blanket', Juniperus horizontalis Moench `Bar Harbor', Pittosporum tobira (Thunb.) Ait. `Compacta Green', Trachelospermum asiaticum (Sie-bold & Zucc.) Nakai `Aslo', Ophiopogon japonicus (Thunb.) Ker-Gawl., and Hemerocallis × `Aztec Gold' was significant and therefore unacceptable. Chemical name used: 3-isopropyl-1H-2,1,3-benzothiadiazin-(4)-3H-one 2,2-dioxide (bentazon).