Growth rate and biomass partitioning of wildtype and low‐gibberellin tomato (Solanum lycopersicum) plants growing at a high and low nitrogen supply

Abstract

The growth‐promoting effects of gibberellins (GAs) on plants are well documented, but a complete growth analysis at the whole plant level on plants with an altered GA biosynthesis has never been reported. In the present work, the relative growth rate (RGR), biomass partitioning and morphological parameters of wildtype (Wt) tomato (Solanum lycopersicum L. cv. Moneymaker) plants were compared with those of isogenic (gib) mutants with a reduced biosynthesis of gibberellins. GA deficiency reduced RGR and specific leaf area (SLA, leaf area per unit leaf mass) and increased the net assimilation rate (NAR, the rate of biomass increment per unit leaf area). Despite the free access to nitrogen in the rooting medium, the low‐GA mutants had a much higher root mass ratio (RMR, the root mass per unit plant biomass) than the Wt, suggesting that the mutants were disturbed in their growth response to nitrate supply. The experiment was repeated at a low exponential nitrate supply, which forced all plants to grow at the same low RGR. The persistence of the differences in RMR at low N‐supply indicated that the high RMR of the mutants was a direct effect of low GA, which was independent of nitrate supply. Because the low N‐supply increased the RMRs of all genotypes to the same extent, the response of RMR to N‐supply does not seem to depend on GA. Although many of the traits of the slow growing GA mutants were very similar to those of inherently slow growing plant species from unproductive habitats, gibberellins are unlikely to be a main determinant of a plant's potential RGR.

The influence of gibberellic acid and sulfur fertilization rate on growth and S-use efficiency of mustard (Brassica juncea)

“…The increase in dry mass accumulation was due to the increase in RGR and specific leaf area at sufficient level of S. However, an increase in NAR at the excess level of S was due to full exposure of lesser number of leaves to photosynthetically active radiation without shading effect. The results on promotive effect of GA 3 on photosynthetic rate and growth have been reported earlier also (Khan, 1996;Nagel et al, 2001). These results are supported from the observation of Nagel et al (2001) that low GA mutant had a lower RGR and reduction in RGR was associated with a reduction in SLA.…”

“…It was hypothesised that if plants were managed for better use of N, photosynthesis and enhanced shoot growth with the use of GA 3 , it could lead to increased S-use efficiency (SUE) of the crop. Research has shown that GA 3 promotes growth (Rood et al, 1990;Khan, 1996;Khan et al, 1998Khan et al, , 2002a; Nagel et al, 2001), photosynthesis (Khan 1996;2002b;Khan and Samiullah, 2003) and nitrogen utilization (Khan et al, , 1998(Khan et al, , 2002bNagel and Lambers, 2002). The reported research was, therefore, conducted to determine the effects of GA 3 spray at the whole plant level on growth, photosynthesis, N accumulation and its implication on SUE (proportion of applied S recovered by the plants) of mustard under different levels of S.…”

The Control of Carbon Acquisition by and Growth of Roots

“…There are also correlations between cytokinin status of shoots and roots, export of cytokinins from roots, and reduced root growth (Beck 1996). Low GA mutants of tomato have relatively much more root (Nagel et al 2001). It is not at all clear if any of these processes are of importance in wild-type plants, and, although the evidence from low-hormone mutants is particularly interesting, there is no obvious logic to a range of plant growth substances having an effect on root growth.…”

Genetic and Physiological Architecture of Early Vigor in Aegilops tauschii, the D-Genome Donor of Hexaploid Wheat. A Quantitative Trait Loci Analysis

“…As far as leaf (and sheath) length and underlying traits are concerned, it is striking that the genes, encoding enzymes of the early steps of the GA biosynthetic pathway in rice, are all positioned on chromosomes that harbor QTLs for leaf length and underlying traits in A. tauschii (Gale and Devos, 1998;Sakamoto et al, 2004). Since GA affects leaf expansion, SLA, and RGR in several species (Dijkstra et al, 1990;Nagel et al, 2001;Bultynck and Lambers, 2004), it is worthwhile to consider the involvement of GA-related genes in early vigor traits. Alternative candidate genes can perhaps be found in the carbon metabolism pathways.…”