Terri I. Kirk’s research while affiliated with Purdue University West Lafayette and other places

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-(phenylmethy)-1H-purine 6-amine (benzyladenine).

O poder de penetração das raízes no solo tem sido estudado com vistas a cultivos agrícolas, porém não há dados no que se refere a substratos em recipientes. Neste trabalho avalia-se a impedância mecânica de: areia, perlita, turfa, fibra-de-coco e misturas do mercado internacional: Fafard nº 2, Fafard 2P, Jiffy 7 e Oasis. Amostras secas e saturadas foram analisadas sob quatro níveis de compactação. Jiffy 7 e Oasis foram analisados na densidade original, conforme fabricação. Avaliou-se a impedância através de um pino metálico acoplado em micropenetrômetro digital. A pressão de penetração correlaciona-se com a compactação do substrato, apresentando interação significante entre grau de compactação e nível de umidade.The penetration power of the roots into the soil has been studied in relation to field crops but not to container media. In this work the mechanical impedance of sand, perlite, peat, coir and commercial mixtures were evaluated: Fafard, no 2, Fafard 2P, Jiffy 7 and Oasis. Dry and saturated samples were analyzed under four levels of compactation. Jiffy 7 and Oasis were analyzed only in the original density of the manufactured products. The impedance was measured by a metal probe and a digital micropenetrometer. The penetration pressure is correlated to the level of compactation of the media, with significant interaction between compactation and moisture level.

The penetration power of the roots into the soil has been studied in relation to field crops but not to container media. In this work the mechanical impedance of sand, perlite, peat, coir and commercial mixtures were evaluated: Fafard no 2, Fafard 2P, Jiffy 7 and Oasis. Dry and saturated samples were analyzed under four levels of compactation. Jiffy 7 and Oasis were analyzed only in the original density of the manufactured products. The impedance was measured by a metal probe and a digital micropenetrometer. The penetration pressure is correlated to the level of compactation of the media, with significant interaction between compactation and moisture level.

The force applied to fill containers with growing media in greenhouses results in varying packing densities. The physical properties of the medium also vary with packing densities. The influence of the packing density on the penetrability of five media (sand, perlite, Sphagnum peat, coir and a commercial mixture Fafard 2P ® (60% S. peat + perlite) was studied. Four levels of compaction were applied: 1. loose (no compaction); 2. firmed (the bulk density determined in lab); 3. compacted (middle point between levels 2 and 4); 4. "maximal" compaction that could be obtained by hand. The substrates were analyzed at the moisture content as received and at container capacity. The pressure needed to penetrate a pointed metal probe of 6.5 mm diameter vertically 3.5 cm into the medium was measured by a penetrometer. The mechanical impedance significantly increased for all substrates with increasing packing density. A significant interaction between the moisture level and the applied packing density was observed. Loosely packed samples showed higher mechanical impedance when the moisture content was at container capacity as compared with the drier samples, with exception of Fafard 2P®; maximal compacted samples showed higher mechanical impedance at the lower moisture content.

Two years of floriculture greenhouse industry root media analysis results from the Purdue University Greenhouse Media Testing Laboratory were studied for nutritional trends. Root media analysis results were statistically analyzed over 72 categories by crop, time, and firm. Sixty‐five percent of samples were submitted in the spring and fall, during the period of highest production of greenhouse crops. The largest number of samples were from: roses (21.5%), poinsettias (14.5%), and geraniums (8%). Of the samples received, 87% came from 32 firms. The mean pH level for all samples was 6.32, which is above the acceptable range for most crops of 5.8 to 6.0 for soilless root media. In addition, 63% of all samples were also above the acceptable pH range. There were also a large percentage of samples that contained excessive levels of magnesium (Mg) [39.4%], potassium (K) [27.4%], and phosphorus (P) [27.4%]. Our analysis suggests the need for growers to purchase pH and soluble salt meters to regularly monitor greenhouse root media pH and soluble salts during the production cycle. This analysis provides us with data useful in developing educational programs targeted at problem areas in greenhouse nutrition.

Nellie White' Easter lilies were grown under two day/night temperature regimes, a positive differential temperature (+DIF) of 15.5C night / 21C day temperature or a negative differential temperature (-DIF) of 19.4C night / 14.4C day temperature. At anthesis the plants were divided into 15 leaf-node segments, starting from the plant base (nodal position 0-15). The segments were further subdivided into leaf, stem and flower tissue parts, with fresh and dry weights being recorded, and tissue being analyzed for NH 4 -N, P, K, Ca, Mg, Na, Cu, B, Fe, Mn, and Zn. Of the elements studied, only P content was statistically different at the DIF treatment × nodal position × tissue type interaction. Total 1eaf P per segment was higher in the -DIF plants, with the concentration increasing from 0.19 mg at nodal position O-15 up to the 1.34 mg at nodal position 46-60, compared to 0.16 and 0.76 mg, respectively, for the +DIF plants. There were also significant differences at the DIF treatment × tissue type, with -DIF leaf tissue having a higher total content of P, K, Mg, Ca, Na and B, while Cu was lower, than the +DIF leaf tissue. Results indicate that the distribution of nutrients in Easter lily plants are affected by growing temperature regimes.

The possible factors contributing to leaf yellowing during the postharvest phase of Easter lilies (Lilium longiflorum Thunb.) were investigated. Higher levels of growth retardants, forcing under negative DIF conditions, cold storage (4.0°C) at the `puffy bud' stage and shipping stress were shown to increase leaf yellowing during postharvest holding. Concentrations of soluble carbohydrates and starch under inductive and non-inductive conditions were determined to investigate the correlation of it to leaf yellowing. Lilies grown under negative DIP had lower concentrations of leaf, stem and flower soluble carbohydrates and starch compared to plants grown under positive DIF. Investigation of diurnal fluctuations of leaf carbohydrates revealed low carbohydrate levels in negative DIP-forced plants at all times during the diurnal cycle. Supplemental light (50-60 μmo1 m ⁻² s ⁻¹ ) during cold storage increased leaf carbohydrate levels. Higher levels of bud abortion and reduced flower longevity were also observed under conditions inductive of leaf yellowing.

Commercial greenhouse operators are increasingly using “negative DIF” temperature regimes to control crop height. A negative DIF exists when greenhouse night temperature is greater than the day temperature. Large negative differences in day and night temperatures strongly suppress stem elongation in many crops. We have explored the effects of negative DIF temperature regimes on leaf, flower, and stem carbohydrate levels in Lilium longiflorum Thunb. `Nellie White'. During two growing seasons, `Nellie White' plants were grown under positive or negative DIF regimes (±5 or 8C) under prevailing daylengths, with temperatures adjusted so that daily temperature averages were equal between regimes. Plants were harvested ≈10 days after visible bud stage and at anthesis. Carbohydrates in stems, leaves, and flowers were analyzed by high-performance liquid chromatography. Compared to plants grown under positive DIF, negative DIF plants showed significantly reduced stem length and leaf and stem dry weights. Negative DIF regimes reduced leaf and stem total soluble carbohydrate (TSC) content by 39% to 46% at visible bud and anthesis, while flower TSC content was reduced by 10% to 13%.

Commercial greenhouse operators are increasingly using “negative DIF” temperature regimes for crop height control. A negative DIF exists where the night temperature (NT) is greater than day temperature (DT). Large differences in DT-NT strongly suppress stem elongation in many crops, and have been used to reduce labor and material costs for chemical growth regulator applications on Easter lily. We have explored some of the biochemical effects of negative DIF temperature regimes. 'Nellie White Easter lilies were grown (1989 and 1991) at Purdue under a +10 or -10 DIF regime with temperatures adjusted so that daily averages were equal. Plants were harvested at visible bud (VB) and anthesis. Carbohydrates in stems, leaves and flowers were analyzed by HPLC With both temperature regimes, timing data indicated equal daily temperature averages were achieved. Negative DIF severely reduced stem length, and leaf and stem dry weight. Negative DIF reduced leaf and stem total soluble carbohydrate (TSC) content 39-46% at VB and anthesis, while flower TSC was reduced 10-13%. These results indicate negative DIFs have potentially detrimental biochemical effects on Easter lilies. Other techniques, such as early morning temperature drops, were not a part of this study, and their physiological effects should be evaluated as well.