Remobilization of Carbon and Nitrogen in Wheat as Influenced by Postanthesis Water Deficits

Abstract

Preanthesis stored C and N in wheat (Triticum aestivum L.) are important in a mediterranean climate because grain filling frequently depends on the remobilization of preanthesis assimilates. We determined the effect of the rate of development of postanthesis water deficits on the remobilization of C and N to the grain using stable isotopes of C and N accumulated in the plant during the vegetative phase. Plants were grown in pots with adequate water and under similar temperature and humidity conditions until anthesis, and then were transferred to two temperature and humidity regulated greenhouses, and watering was stopped. One greenhouse was maintained at minimum relative humidity of 80% and the other at 40%. Within 6 d of anthesis the rates of development of plant water deficits became different and for the first 19 d after anthesis they were 0.10 and 0.18 MPa d−1 for the high and low humidity regimes, respectively. Total grain C with fast development of water deficits was reduced by 24%, relative to the slow rate, because postanthesis C assimilation was reduced by 57%, while remobilization of preanthesis stored C was increased by 36%. Total grain N was not affected by the rate of development of water deficits because there was a greater retranslocation of preanthesis N with fast relative to slow development of water deficits and because there was a smaller loss of preanthesis N with fast development of water deficits. Fast development of water deficits reduced losses of preanthesis N from 25% to 6%. The absolute contributions of preanthesis C and N to the grain were 449 and 35 mg plant−1, respectively, with fast development of water deficits. These contributions accounted for 64 and 81% of the total grain C and N, respectively. The gain in grain 13C and 15N in the mainstem and Tiller 1 of plants exposed to rapid development of water deficits, arose not only from remobilization from the straw of those shoots, but also seemed to be supplemented by C and N remobilized from Tillers 2 and 3.

Effect of foliar application of N and humic acids on growth and yield of durum wheat

“…In fact, plant dry matter was the same across treatments until heading, when spikes differed in dry weight. Grain filling and partitioning of assimilates to developing grains are usually affected by post-anthesis water deficit (Broklehurst, 1978;Kobata et al, 1992;Palta et al, 1994). Plants amended with split applications of soil N showed relatively lower 1000-seed weight, probably for the greater number of kernels per spike with respect to other treatments.…”

Effects of varied water regimes on root length, dry matter partitioning and endogenous plant growth regulators in sunflower (Helianthus annuusL.)

“…In traits like TDM, RDM and LAI, drought reduced the days to reach the maximum peak. Extensive studies have demonstrated that water deficits result in early senescence (Kobata et al 1992, Palta et al 1994, Zhang et al 1998). Many factors contribute toward early senescence (Lers et al 1998, Nooden 1988), but ABA is considered the most promising of the early senescence promoters (Nooden 1988, Madhu et al 1999, Tadas et al 1999.…”

Alteração no potencial osmótico e teor de carboidratos solúveis em plantas jovens de lobeira (Solanum lycocarpum St.-Hil.) em resposta ao estresse hídrico

“…Embora o ajustamento osmótico não impeça que a taxa fotossintética seja reduzida sob condições de estresse hídrico (Jones & Rawson 1979), a manutenção da turgescência permite que a fotossíntese e outras importantes atividades fisiológicas sejam mantidas, mesmo que baixas, possibilitando a redistribuição de carbono e nitrogênio (Kobata et al 1992, Palta et al 1994.…”