Jeff S. Kuehny
Jeff S. Kuehny and Patricia Branch
Lateral branches of poinsettia tend to break from the main stem as plants reach maturity. The cause of poor stem strength is not known; however, suggested factors implicated in poor stem strength are: rate of nitrogen fertilizer used, type of plant growth regulator used, crowding of plants, or stem diameter of the cutting. Four different experiments were conducted to determine if these factors affected stem strength of poinsettia. Experiment 1: `Freedom Red', `Success', `V-17 Angelika Red', `Red Sails', `Nutcracker Red', `Cortez', `Maren', and `Red Splendor' poinsettia were fertilized with 20N–1P0–20K at 75, 75/125, 125/200, or 200 ppm N drip fertigation with zero leachate. Experiment 2: Three plant growth regulators were applied to `Pearl' and `Jolly Red' poinsettias. Experiment 3: `Freedom Red' plants were grown in a 625, 900, 1225, or 1600 cm2 area. Experiment 4: Rooted `Freedom Red' cuttings with stem diameters of 4.5, 5.5, 6.5, or 7.5 mm were used. A force meter was used to determine the strength of each lateral on the main stem of the six replications in each experiment. The lower laterals had the least stem strength and the top lateral had the highest stem strength for all treatments in all experiments. The stem strengths of some cultivars in experiment 1 were stronger at the lower fertilizer rates. Type of plant growth regulator had no significant affect on most poinsettia cultivars. The stem strengths of poinsettias in experiments 3 and 4 varied according to which lateral was measured.
Seenivasan Natarajan* and Jeff S. Kuehny
The demand for new and/or improved herbaceous annuals and perennials continues to increase, making information on production and viability of these plants a necessity. In Louisiana and the Southern U.S., one of the greatest impediments to production of marketable herbaceous plants and their longevity is high temperature. Herbaceous plants have various stages of vegetative growth and flowering; high temperatures during these developmental stages can have a tremendous impact on plant metabolism, and thus plant growth and development. The goal of this research was to better understand the differences between heat tolerant (HT) and heat sensitive (HS) species and cultivars at various high temperatures in terms of whole plant growth, flowering, photosynthesis, carbohydrate content, electrolyte leakage, chlorophyll content and plant small heat shock proteins (HSP) expression levels. Salvia splendens Vista Series (HT), Sizzler series (HS); Viola witrokiana `Crystal Bowl Purple' (HT), `Majestic Giant Red Blotch' (HS), F1 Nature Series (HT) and F1 Iona Series (HS); Gaillardia × grandiflora `Goblin' (HT) and Coreopsis grandiflora `Early Sunrise' (HS) were grown from seed in growth chambers under 25/18 °C (day/night) cycles. Plants at 4, 6, and 8 weeks after germination were subjected to different high temperature treatments of 25 (control), 30, 35, 40, and 45 °C for 3 h. Results show that there was a significant difference in net photosynthesis, electrolyte leakage, soluble carbohydrate content and HSP levels between HT and HS cultivars. Effects of high temperature on plant growth, chlorophyll content, and number of days to flower, flower size, and marketable quality were also significantly different.
Seenivasan Natarajan and Jeff S. Kuehny
Many bedding plant cultivars struggle to survive in high temperatures during production. The objective of this research was to study how heat stress and preconditioning affects growth, physiology, and anatomy of the annual bedding plant Salvia splendens Ker Gawl. Heat preconditioning increased the quality and survival capacity of nonheat-tolerant ‘Sizzler Red’. Heat-tolerant traits of ‘Vista Red’ were enhanced with preconditioning. The higher tolerance levels with and without heat preconditioning for ‘Vista Red’ suggested that cultivars with thicker, broader leaves, and higher stomatal frequency had higher light interception, gas exchange, transpirational cooling, and CO2 fixation. These plants attained a more rapid canopy cover and maintained healthier leaves and supplied photoassimilates to reproductive development and root growth. Selecting for these characteristics could be used to help provide guidelines for breeding and selection of heat-tolerant salvia.
Melyssa K. Davis and Jeff S. Kuehny
Herbaceous perennials are one of the fastest growing ornamental sectors in the United States. Current production recommendations do not address the effect of environmental factors, such as high temperature, on growth of herbaceous perennials. The focus of this research was to determine how supra-optimal temperatures effect growth and photosynthesis. Plants were exposed to a high temperature of 35 °C and photosynthesis measurements were recorded over a 6-week period at 1100, 1300, and 1500 hr. Results indicate that the time of day the measurements were taken made little difference on rate of photosynthesis and that there was a similar trend in photosynthetic rate over the 6-week period. Photosynthesis decreased as the plants began to flower and then increased until the onset of flower senescence. Plants grown at supraoptimal and optimal conditions had a similar trend and rate of photosynthesis throughout the 6-week period. Plant growth significantly decreased as the duration of high temperature increased for both species; however, Gaillardia was more heat tolerant then Coreopsis.
Mauricio J. Sarmiento and Jeff S. Kuehny
Curcuma alismatifolia `Chiang Mai Pink' is a tropical perennial from the Zingiberaceae family with attractive flowers that make it useful as potted plant. Curcuma alismatifolia produces a tall inflorescence resulting in an unmarketable plant due to excessive height. Rhizomes of C. alismatifolia were soaked for 10 minutes in GA at concentrations of 0, 100, 200 or 500 ppm. The same plants were drenched with paclobutrazol at 0, 2, 3 or 4 mg a.i./container when shoots were 10 cm. GA significantly delayed rhizome emergence and flowering and reduced flower height. Paclobutrazol significantly reduced height; however, greater concentrations must be applied to obtain a marketable plant height. Number of flowering stems, postproduction life, and postproduction stretching were not affected by GA or paclobutrazol. Curcuma alismatifolia had an excellent postproduction life (4.64 ± 0.28 weeks) with little postproduction stretching (2.27 ± 0.38 cm).
Jeff S. Kuehny, Blanca Morales, and Patricia Branch
Irrigation water quality is an important factor in ornamental plant production; however, there is little information in this area. Saline (NaCl) and alkaline (NaHCO3) water have been shown to cause general chlorosis, tip burn, and defoliation of plants. The growing medium used in crop production may be an important factor when irrigating with saline and alkaline water. Our objectives were to determine the effects of increasing concentrations of NaCl: CaCl2 and NaHCO3 in irrigation water on growth and development of spring and fall bedding plants grown in peat, peat/pine bark, and pine bark media. Plant dry weight, height, and width were significantly lower at 300 and 400 ppm NaCl: CaCl2 and NaHCO3 levels. Early visible symptoms were necrosis of leaf tips, some leaf discoloration and finally plant death in the NaCl: CaCl2 experiment. The leaves of plants in the NaHCO3 experiment became water soaked and chlorotic, and some leaf abscission occurred. The best plant growth in the NaHCO3 experiment occurred in peat and the best plant growth in the NaCl: CaCl2 experiment occurred in pine bark. Decreased uptake of K+, Ca++, and Mg++ occurred when high levels of sodium were present.
Jeff S. Kuehny and William B. Miller
The majority of Hippeastrum bulbs sold in the U.S. market are shipped from other countries. The shipping time and temperature varies by the country that the bulbs are shipped from and the storage time and temperature also varies by the company that packages the bulbs for retail sale. These packaged bulbs then sit on a shelf until they are purchased and forced by the consumer. These various storage times and temperatures can affect the longevity after packaging (premature emergence) and quality of the finished plant. The objectives of this research were to determine the effects of various storage temperatures and durations on emergence and forcing of Hippeastrum hybrids. Bulbs were stored at temperatures of 5, 9, 13, 21, and 29 °C for 6, 9, 12, and 15 weeks after which time one set was stored at 21 °C (packaged display temperature) and the other set forced in the greenhouse. Emergence of leaves and buds when stored at the 21 °C display temperature and during greenhouse forcing varied by specific hybrid according to storage duration at 5, 9 and 13 °C. Storage at 21 and 29 °C resulted in only leaf emergence and no flower bud emergence during the 21 °C display temperature and greenhouse forcing. Storage at 5 and 9 °C generally resulted in slower leaf emergence and quicker bud emergence. Results from this research can be used to help determine the best storage times and temperatures for preventing premature emergence of Hippeastrum based upon previous shipping times and temperatures.
Richard A. Criley and Jeff S. Kuehny
Several reports suggest that late-planted rhizomes of Curcuma alismatifolia produce their inflorescences in less time than those that have been planted earlier in the forcing season. Two cultivars of this ginger species were removed from the ground in late February following a lengthy dormancy period in the field. About 6 weeks later, after air drying, weekly plantings were initiated through the end of June. Five rhizomes per cultivar were planted singly in 15-cm pots in ProMix BX medium. All plants were forced outdoors under full sun conditions and an overhead spray stake irrigation system that delivered 200 ppm each of nitrogen and potassium with each watering. Cultivar differences were apparent. Plant-to-sprout days for the DP and LP cultivars ranged from 20–51 and 21–57 days, respectively, with means of 3 8 ± 9.2 and 44 ± 11.9 days, respectively, over the 10-week planting cycle. Sprout-to-flower days showed much less difference with ranges of 61–75 and 58–72 days for DP and LP and means of 69 ± 4.3 and 66 ± 4.0 days, respectively. Plant to flower times differed largely because of the length of time required for the rhizomes to sprout rather than for the amount of time spent in inflorescence initiation and development. Plant heights at flowering and inflorescence counts were not different within cultivars over the 10-week planting period. Degree days and solar integrals will be presented for the 10 growing periods.
Jeff S. Kuehny and Mary C. Halbrooks
Research defining actual changes in weight gain of roots and shoots during growth episodes of woody ornamentals is limited. The objective of this study was to develop a better understanding of the patterns of root and shoot growth, nitrogen uptake, and changes in carbohydrate and protein content of Ligustrum japonicum, an episodic species. Shoot elongation and lateral root formation were synchronous. The greatest increase in shoot percent of whole plant fresh weight occurred after shoot elongation however, and the greatest increase in root percent of whole plant fresh weight occurred during shoot elongation. Nitrate uptake was highest during shoot elongation and lateral root formation. Carbohydrate and protein content also varied with each episode of growth.