Growth and reproduction of Arabidopsis thaliana in relation to storage of starch and nitrate in the wild‐type and in starch‐deficient and nitrate‐uptake‐deficient mutants

Abstract

We have investigated the interactions between resource assimilation and storage in rosette leaves, and their impact on the growth and reproduction of the annual species Arabidopsis thaliana. The resource balance was experimentally perturbed by changing (i) the external nutrition, by varying the nitrogen supply; (ii) the assimilation and reallocation of resources from rosette leaves to reproductive organs, by cutting or covering rosette leaves at the time of early flower bud formation, and (iii) the internal carbon and nitrogen balance of the plants, by using isogenic mutants either lacking starch formation (PGM mutant) or with reduced nitrate uptake (NU mutant).When plants were grown on high nitrogen, they had higher concentrations of carbohydrates and nitrate in their leaves during the rosette phase than during flowering. However, these storage pools did not significantly contribute to the bulk flow of resources to seeds. The pool size of stored resources in rosette leaves at the onset of seed filling was very low compared to the total amount of carbon and nitrogen needed for seed formation. Instead, the rosette leaves had an important function in the continued assimilation of resources during seed ripening, as shown by the low seed yield of plants whose leaves were covered or cut off. When a key resource became limiting, such as nitrogen in the NU mutants and in plants grown on a low nitrogen supply, stored resources in the rosette leaves (e.g. nitrogen) were remobilized, and made a larger contribution to seed biomass. A change in nutrition resulted in a complete reversal of the plant response: plants shifted from high to low nutrition exhibited a seed yield similar to that of plants grown continuously on a low nitrogen supply, and vice versa. This demonstrates that resource assimilation during the reproductive phase determines seed production.The PGM mutant had a reduced growth rate and a smaller hiomass during the rosette phase as a result of changes in respiration caused by a high turnover of soluble sugars (Caspar et al. 1986; W. Schulze et al. 1991). During flowering, however, the vegetative growth rate in the PGM mutant increased, and exceeded that of the wildtype. By the end of the flowering stage, the biomass of the PGM mutant did not differ from that of the wild-type. However, in contrast to the wild-type, the PGM mutant maintained a high vegetative growth rate during seed formation, but had a low rate of seed production. These differences in allocation in the PGM mutant result in a significantly lower seed yield in the starchless mutants. This indicates that starch formation is not only an important factor during growth in the rosette phase, but is also important for whole plant allocation during seed formation. The NU mutant resembled the wild-type grown on a low nitrogen supply, except that it unexpectedly showed symptoms of carbohydrate shortage as well as nitrogen deficiency.In all genotypes and treatments, there was a striking correlation between the concentrations of nitrate and organic nitrogen...

Isolation and Characterization of Mutants of Common Ice Plant Deficient in Crassulacean Acid Metabolism

“…The slow-growth phenotype is similar to that observed for the starchless mutant of Arabidopsis deficient in chloroplast PGM activity also grown under a 12-h photoperiod (Caspar et al, 1985), but not for the starchless mutant of N. sylvestris defective in plastid PGM grown under a 16-h light photoperiod (Hanson and McHale, 1988). Floral initiation can be delayed and seed production reduced by up to 50% in starch-deficient mutants of Arabidopsis (Schulze et al, 1994;Yu et al, 2000). However, the 90% reduction in seed number from line 351 greatly exceeded that predicted just from starch deficiency alone and is comparable to the reduction in reproductive output reported when common ice plants were deprived of CO 2 each night to minimize nocturnal carbon gain (Winter and Ziegler, 1992).…”

Improving Plant Nitrogen Use Efficiency through Alteration of Amino Acid Transport Processes

“…This suggests that, under insufficient N nutrition, the transgenic plants remobilize more N, probably triggered by improved sink strength ( Fig. 5C; CraftsBrandner and Egli, 1987;Schulze et al, 1994;Lemaître et al, 2008;Masclaux-Daubresse et al, 2008;MasclauxDaubresse and Chardon, 2011). Indeed, NUtE was improved significantly in the AAP1-OE plants under low and moderate N conditions (Fig.…”

The Autophagic Degradation of Chloroplasts via Rubisco-Containing Bodies Is Specifically Linked to Leaf Carbon Status But Not Nitrogen Status in Arabidopsis

“…The majority of plant nitrogen and other nutrients are distributed to leaves in the vegetative growth stage (Schulze et al, 1994;Makino et al, 1997). In C 3 plants, 75% to 80% of total leaf nitrogen is distributed to chloroplasts, primarily as photosynthetic proteins such as Rubisco (Makino and Osmond, 1991;Makino et al, 2003).…”