Leaves were collected in 1974 and 1975 from mature ‘Tonnage’, ‘Lula’, ‘Taylor’, and ‘Booth 8’ avocado trees (Persea americana Mill.) on sand, muck, and calcareous rock soils and analyzed for N, P, K, Ca, Mg, Mn, Cu, Zn, and Fe. Significant differences in levels of all 9 elements in ‘Tonnage’ leaves occurred among the 3 soil types. Crop size, fertilization, soil pH, soil Ca level, and exchange capacity of the soil appeared to be important factors in the variations. Differences in concentration of N and P were not significant among the 4 cultivars but were significant for the other elements.
As leaves of ‘Tonnage’ avocado (Persea americana Mill.) increased in age, N, P, and K contents decreased, while Ca, Mg, Mn, Cu, Zn, and Fe contents were higher. A comparison of leaves from 1st and 2nd flushes showed similar trends reflected in leaf age. The basal leaf was lower in P but higher in Ca, Mg, and Cu when compared with the terminal leaf of the same twig. Only N and Cu contents were different when leaves from fruiting and nonfruiting twigs were compared. Practical application of the data in sampling avocado leaves is discussed.
As mango leaves increased in age, lower P and K contents were found, while Ca content was higher. The basal leaf was lower in N and Ca but higher in P and K contents when compared with the terminal leaf of the same shoots. Only small differences were observed when leaves were compared from fruiting and nonfruiting shoots. The practical application of data in sampling mango leaves is discussed.
Yields and quality were compared on young bearing ‘Bearss’ lemon (Citrus limon L.) trees grown with 3 rates of N and K and 2 levels of soil moisture over a 4-year period. Increased rates of N application increased fruit production, incidence of fruit with scab, and green fruit; and decreased acid content of juice. Potassium applications increased the acid content of juice. Irrigation increased fruit size and decreased the number of green fruit after curing. A leaf N content of 2.2 to 2.6% is suggested for optimum fruit production for ‘Bearss’ lemon under Florida conditions.
Though high electrical conductivity (EC) levels are commonly held to be the primary limiting factor for using spent mushroom compost (SMC) as a growing substrate, EC can be reduced by leaching. This allowed SMC to be successfully used for growing plants. Leaching reduced EC of the substrate solution from as high of 30 dS·m-1 (mmhos·cm-1) to 2 to 3 dS·m-1, a level acceptable for growing plants. The initial EC and container capacity determined the number of leachings and total volume of water required to lower EC of SMC substrates to acceptable levels. As the concentration of SMC was increased, a higher number of leachings or larger volume of water were required to adequately reduce EC levels. In trials spanning 2.5 years, SMC was effectively used as a substrate in the production of marigold (Tagetes patula) `Yellow Girl'. Benefits to plant growth from SMC incorporation included a slow release of nutrients as the SMC decomposed and a good air-filled pore space/water-holding capacity when amended with a commercial nursery mix. From these trials, it is recommended that SMC be incorporated at rates of 25% to 50%. It is not recommended that SMC be used in concentrations over 50% because the EC may be too difficult to manage and the high levels of air-filled pore space of SMC. Though season may affect the initial EC level of SMC, such variation is minimized by leaching while differences in plant response are more likely to be attributed to environmental conditions. No differences in plant growth were observed among SMC sources.
`Spears' (nonpinched and pinched) and `Yellow Mandalay' (pinched) chrysanthemums were grown in growth chambers equipped with panels filled with liquids that served as spectral filters. Light quality was altered by reducing blue light, increasing red: far-red (R: FR) light, or reducing R: FR. Control panels did not selectively alter light transmission. Photosynthetic photon flux was the same in all chambers. All plants grown under increased R: FR filters had reduced height, reduced internode length, and increased chlorophyll content compared to controls. Reduction in blue light decreased chlorophyll content of pinched plants compared to controls. Pinched plants grown under increased R: FR light and !ong days developed fewer nodes than controls due to the formation of abnormal capitula; the controls and plants from the other treatments developed more nodes before producing similarly abnormal capitula. Stem diameter and leaf area did not differ due to treatments.
Shading (92%) of `Redchief Delicious' apple (Malus domestics Borkh.) trees for 10-day periods from 10 to 20, 15 to 25, 20 to 30, and 25 to 35 days after full bloom (DAFB) caused greater fruit abscission than shading from 5 to 15, 30 to 40, 35 to 45, or 47 to 57 DAFB. Fruit 8 to 33 mm in diameter (10 to 30 DAFB) were very sensitive to 10 days of shade, even though fruit sizes of 6 to 12 mm are considered the most sensitive to chemical thinners. In a second test, shading for 3 days caused fruit thinning; 5 days of shade in the periods 18 to 23, 23 to 28, and 28 to 33 DAFB caused greater thinning than 11 to 16 or 33 to 38 DAFB. Shading reduced photosynthesis (Pn) to about one-third that of noncovered trees. Terbacil (50 mg·liter-1) + X-77 surfactant (1250 mg·liter-1) applied with a hand-pump sprayer 5, 10, or 15 DAFB greatly reduced fruit set and caused some leaf yellowing, particularly in the earliest treatments. Terbacil reduced Pn by more than 90% at 72 hours after application. Shoot growth of trees defruited by shade or terbacil was equivalent to defruited or deblossomed trees; ethephon (1500 mg·liter-1) inhibited tree growth and defruited trees. No terbacil residues were dectected in fruit at harvest from applications made 5, 15, 20, 25, or 30 DAFB. Eleven of 12 photosynthesis-inhibiting herbicides were also found to thin `Redchief Delicious' apple trees. Shading caused more thinning than terbacil at the later applications, which may reflect poorer absorption and/or lesser photosynthetic inhibition than when terbacil was applied to older leaves.
Mature zygotic embryos dissected from ginseng (Panax ginseng C.A. Meyer) seeds were cultured on Murashige and Skoog (MS) medium containing various concentrations of 2,4-D and kinetin. Somatic embryos were induced directly from cotyledonary tissue and from intervening callus. The frequency of somatic embryo induction was up to 55% of zygotic embryo explants. Upon transfer onto half-strength MS medium supplemented with 1 mg BA/liter and 1 mg GA3/liter, most somatic embryos developed into plantlets. More than 50% of the plantlets flowered after 4 weeks of culture, and some developed immature fruits in vitro. These results indicate that adulthood of ginseng root explants is not a prerequisite for flowering of plantlets regenerated through somatic embryogenesis. Chemical names used: (2,4 -dichlorophenoxy) acetic acid (2,4-D); N-(2-furanylmethyl) -1H-purin-6-amine(kinetin); N-(phenylmethyl) -1H-purin-6-amine (BA); gibberellic acid (GA3).