Young tomato plants were grown at different day and night temperature combinations with an average of 21°C. Some combinations with a different average 24-h temperature were included. Day temperature (Td) varied between 16 and 26°C, night temperature (Tn) between 12 and 26°C, while the daylength was 12h. Light intensity was about 26 W m−2 photosynthetic active radiation (PAR).An inversed temperature regime (Td lower than Tn) reduced plant growth (fresh weight, FW; dry weight, DW) and development (number of leaves, number of trusses). Reduction in development was less than reduction in growth. Growth reduction was caused by a lowering of the leaf area ratio (LAR). The decrease in LAR at an inversed temperature regime was caused mainly by a decrease in specific leaf area (SLA). Net assimilation rate (NAR) was not influenced by the temperature regime. For young widely spaced plants a lower SLA (thicker leaves) results in less light interception and thus in growth reduction.It is possible now to explain the different reactions on temperature regime at the same temperature intergral between young plants and closed canopies. In a closed canopy (a producing crop) differences in leaf area index, brought about by differences in leaf thickness, have hardly any influence on light interception because most light has been already intercepted anyway. This explains why a producing crop, in contrast to young plants, shows hardly any reaction to temperature regime at the same temperature integral.A regression analysis indicated that for FW and DW, plant length, leaf area (A), number of leaves, number of trusses, relative growth rate (RGR), LAR and SLA, Td is more important than Tn.
"Day and night temperatures can be manipulated to control plant height in ornamental plants. For many species, warmer day than night temperature promotes stem elongation more than constant or cooler day than night temperatures (Heuvelink, 1989; Erwin et al., 1989; Moe, 1990; Al-Said, 2000). This was also found to be true in this study for cauliflower. "
[Show abstract][Hide abstract] ABSTRACT: Two experimental runs were conducted to assess the response of the growth and development of cauliflower (Brassica oleracea L. var. botrytis) cv. "Nautilus" F1 hybrid after curd initiation to different day and night temperatures in Saxcil Growth environmental cabinets, which were set to run at 24/12°C, 12/24°C, 20/16°C, 16/20°C, 20/20°C (1st Run) and 24/20°C, 20/12°C and 20/16°C (2nd Run) with a total irradiance of 441 μ mols m-2 s-1 (90 Watts m-2) at the School of Biological Sciences, University of Reading, United Kingdom. Greater rates of curd growth (curd length, diameter, fresh and dry weights) were achieved at warmer night temperatures than day temperatures, whilst greater leaf and stem growth (leaf area, stem length, fresh and dry weights) were achieved when day temperatures were warmer than night temperatures, even with the same mean temperatures. Greater curd growth (curd length, diameter, fresh and dry weights) were achieved at warmer night temperatures than day temperatures. Similarly greater Relative Curd Growth Rate (RCGR) was recorded in plants grown at warmer night than day temperature (12/24°C) compared to the plants grown at cooler night than day temperature (24/12°C). Moreover, RCGR decreased significantly (p<0.01) with increase in day temperature (DT) and increased significantly (p<0.01) with increase in night temperature (NT). Similarly, curd length, diameter, fresh and dry weights decreased with increase in DT and increased with increase in NT. Further, cauliflower stem length (SL) was linearly related to the effective mean temperature with optimum day temperature of 24°C and optimum night temperature of 12°C.
Pakistan Journal of Botany 04/2013; 45(2):411-420. · 0.82 Impact Factor
"The DIF concept was introduced by Erwin et al. (1989) and has since become widely used for growth control in greenhouse production of ornamental plants. A negative DIF treatment often results in reduced total plant dry weight as compared with a positive DIF (Heuvelink, 1989; Myster et al., 1997; Xiong et al., 2002). Gibberellins (GAs) are hormones contributing to the control of growth and development of plants throughout their life cycle and have been known for decades for their strong growth-promoting effect on stems. "
[Show abstract][Hide abstract] ABSTRACT: Active gibberellin (GA(1)) is an important mediator of thermoperiodic growth in pea. Plants grown under lower day than night temperature (negative DIF) elongate less and have reduced levels of GA(1) compared with plants grown at higher day than night temperature (positive DIF). By comparing the wild type (WT) and the elongated DELLA mutant la cry(s), this study has examined the effect of impaired GA signalling on thermoperiodic growth, photosynthesis, and respiration in pea. In the WT a negative DIF treatment reduced stem mass ratio and increased both root mass ratio and leaf mass ratio (dry weight of specific tissue related to total plant dry weight). Leaf, root and stem mass ratios of la cry(s) were not affected by DIF. Under negative DIF, specific leaf area (projected leaf area per unit leaf dry mass), biomass, and chlorophyll content of WT and la cry(s) plants were reduced. Young, expanding leaves of plants grown under negative DIF had reduced leaf area-based photosynthetic capacity. However, the highest photosynthetic electron transport rate was found in fully expanded leaves of WT plants grown under negative DIF. Negative DIF increased night respiration and was similar for both genotypes. It is concluded that GA signalling is not a major determinant of leaf area-based photosynthesis or respiration and that reduced dry weight of plants grown under negative DIF is caused by a GA-mediated reduction of photosynthetic stem and leaf tissue, reduced photosynthesis of young, expanding leaves, and reduced growth caused by low temperature in the photoperiod.
"In a study carried out in eggplant it was observed that NAR increased as the temperature rose and declined with time. However, this increase in the plant grown at 30 o C reached the maximum value of 0.15 g cm -2 day -1 and then as the temperature decreased to 16 o C it reached the value of 0.03 g cm -2 day -1 (Heuvelink 1989). Both in this study and in other similar studies, the increased NAR depending on time in the first periods of plant growth was slower at low temperature than at high temperature. "
[Show abstract][Hide abstract] ABSTRACT: Changes in plant growth viz. leaf area, leaf weight ratio, root weight ratio, dry leaf weight, dry root weight, total plant dry weight, specific leaf area, leaf thickness, leaf area ratio, net assimilation rate and relative growth rate due to the effects of environmental conditions such as temperature and light intensity were described by plant growth models. All equations produced for growth parameters were affected by light intensity and temperature. From multi-regression analysis, close relationships were found between actual and predicted growth parameters. The regression coefficients (r2) of the equations for growth parameters varied from 0.95 to 0.99 for cultivar Ecdogelb and 0.83 to 0.99 for cultivar Ecdorot, respectively.
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