Search Results

You are looking at 1 - 10 of 11 items for :

  • All content x
Clear All
Free access

Grete Waaseth, Roar Moe, Royal D. Heins, and Svein O. Grimstad

Varying photothermal ratios (PTR) were supplied to Salvia ×superba Stapf `Blaukönigin' during pre-inductive vegetative development with the exception of a short germination period under uniform conditions. In addition, both unvernalized plants and plants receiving a saturating vernalization treatment of 6 weeks at 5 °C were given two photosynthetic photon flux (PPF) levels (50 or 200 μmol·m-2·s-1) during subsequent inductive 16-hour long days. There were no effects of PTR treatments during vegetative development on subsequent flowering. However, the higher PPF level during inductive long days significantly accelerated floral evocation in unvernalized plants, lowering the leaf number at flowering. The effect was practically negligent after the vernalization requirement was saturated. In a second experiment, varying periods (4, 7, 10, and 14 days or until anthesis) at a PPF of 200 μmol·m-2·s-1 during 20-hour days were given at the beginning of a long-day treatment, either with or without preceding vernalization treatment. Flowering percentage increased considerably as the period at 200 μmol·m-2·s-1 was extended compared with plants grown at a lower PPF of 50 μmol·m-2·s-1. However, the leaf number on flowering plants was not affected, except in unvernalized plants receiving the highest PPF continuously until anthesis, where leaf number was reduced by almost 50%. We propose that the PPF-dependent flowering is facilitated either by the rate of ongoing assimilation or rapid mobilization of stored carbohydrates at the time of evocation. Abortion of floral primordia under the lower PPF (50 μmol·m-2·s-1) irrespective of vernalization treatment indicates that the assimilate requirement for flower bud development is independent of the mechanism for floral evocation.

Free access

Bin Liu and Royal D. Heins

Photothermal ratio (PTR) is defined as the ratio of radiant energy (light) to thermal energy (temperature). The objective of this study was to quantify the effect of PTR during the vegetative (PTRv) and reproductive phase (PTRr) on finished plant quality of `Freedom' poinsettia. In Expt. I, plants were grown under 27 combinations of three temperatures, three daily light integrals (DLI), and three plant spacings from pinch to the onset of short-day flower induction and then moved to a common PTR until anthesis. In Expt. II, plants were grown under a common PTR during the vegetative stage and then assigned to nine combinations of one temperature, three DLIs, and three plant spacings after the onset of short-day flower induction. Both PTRr and PTRv affected final plant dry weight. All components of dry weight (total, stem, green leaf, and bract) responded in a linear way to PTRr and in a quadratic way to PTRv. Stem strength was more dependent on PTRv than PTRr. When PTRv increased from 0.02 to 0.06 mol/degree-day per plant, stem diameter increased about 24% while stem strength increased 75%. The size of bracts and cyathia was linearly correlated to PTRr, but not affected by PTRv. When PTRr increased from 0.02 to 0.06 mol/degree-day per plant, bract area, inflorescence diameter, and cyathia diameter increased 45%, 23%, and 44%, respectively.

Free access

Carme Biel, Robert Savé, Abdessamad Habrouk, Josep Maria Espelta, and Javier Retana

research was funded by the PETRI project PTR1995-0511-OP and AGRIGAS.

Free access

Juan J. Ruiz, Jaime Prohens, and Fernando Nuez

This research was supported by the Comisión Interministerial de Ciencia y Tecnología through the projects AGF92-0435, AGF95-0852, and PTR94-0136. The cost of publishing this paper was defrayed in part by the payment of page charges. Under postal

Free access

Bin Liu and Royal D. Heins

Light (radiant energy) and temperature (thermal energy) affect quality of greenhouse crops. Radiant energy drives photosynthesis and, consequently, plant biomass accumulation. Thermal energy is the primary environmental factor driving developmental rate. The concept of a photothermal ratio (PTR), the ratio of radiant energy [moles of photosynthetic (400 to 700 nm) photons/m2] to thermal energy (degree-day), was proposed to describe the balance between plant growth and plant development in greenhouse crops. The objective of this study was to quantify the effect of PTR during vegetative (PTRv) or reproductive (PTRr) phases on finished plant quality of `Freedom' poinsettia (Euphorbia pulcherrima Willd. ex Klotzsch). In Expt. 1, plants were grown under 27 combinations of three constant temperatures (19, 23, or 27 °C), three daily light integrals (DLIs) as measured by the number of photosynthetic (400 to 700 nm) photons (5, 10, or 20 mol·m-2·d-1), and three plant spacings (15 × 15, 22 × 22, or 30 × 30 cm) from pinch to the start of short-day flower induction, and then moved to a common PTR until anthesis. In Expt. 2, plants were grown under a common PTR during the vegetative stage and then moved to combinations of three DLIs (5, 10, or 15 mol·m-2·d-1) and three plant spacings (25 × 25, 30 × 30, or 35 × 35 cm) at a constant 20 °C from the start of short days until anthesis. Both PTRr and PTRv affected final plant dry weight (DW). All components of DW (total, stem, leaf, and bract) increased linearly as PTRr increased, and responded quadratically to PTRv, reaching a maximum when PTRv was 0.04 mol/degree-day per plant. Stem strength depended more on PTRv than PTRr. When PTRv increased from 0.02 to 0.06 mol/degree-day per plant, stem diameter increased ≈24%, while stem strength increased 75%. The size of bracts and cyathia increased linearly as PTRr increased, but was unaffected by PTRv. When PTRr increased from 0.02 to 0.06 mol/degree-day per plant, bract area, inflorescence diameter, and cyathia diameter increased 45%, 23%, and 44%, respectively.

Free access

Tasneem M. Vaid, Erik S. Runkle, and Jonathan M. Frantz

ratio (PTR; ratio of radiant energy to thermal energy). In poinsettia, plant quality attributes including dry weight, bract size, and stem strength decreased as the PTR decreased ( Liu and Heins, 2002 ). In this study, the inverse relationship between

Full access

James E. Faust and Joanne Logan

environmental parameters has been explored in several studies. The concept of photothermal ratio (PTR) was introduced by Liu and Heins (2002) . This concept suggests that plant quality is directly related to the ratio of DLI to the average daily temperature

Free access

Xue Li, Chen Zang, Hang Ge, Jing Zhang, Donald Grierson, Xue-ren Yin, and Kun-song Chen

Nt4CL1 (O24145), Nt4CL2 (O24146); Arabidopsis thaliana At4CL1 (NP_175579), At4CL2 (NP_188761), At4CL3 (NP_176686); Populus tremuloides Ptr4CL1-2 (AAC24503-4); Populus tomentosa Pto4CL1 (AAL02145.1); Lolium perenne Lp4CL1-3 (AAF37732-4); Oryza

Open access

Prashant Bhandari and Tong Geon Lee

, S.R. Feder, A. Giovannoni, J.J. Smart, C.D. Peeters, N. Martin, G.B. 2019 The Ptr1 locus of Solanum lycopersicoides confers resistance to race 1 strains of Pseudomonas syringae pv. tomato and to Ralstonia pseudosolanacearum by recognizing

Free access

Honghui Gu, Jiansheng Wang, Huifang Yu, Zhenqing Zhao, Xiaoguang Sheng, Jisuan Chen, and Yingjun Xu

.A. 2012 NRT/PTR transporters are essential for translocation of glucosinolate defence compounds to seeds Nature 488 531 534 Piao, C.S. Gao, S. Lee, G.H. Kim, D.S. Park, B.H. Chae, S.W. Kim, S.H. 2010 Sulforaphane protects ischemic injury of hearts through