Kernel Set at Low Water Potential Does Not Vary with Source/Sink Ration in Maize

Abstract

Water deficits during pollination increase the frequency of zygotic abortion in maize (Zea tnays L.). Recent work suggests that reproductive failure occurs because assimilate supply in water-deficient plants is not sufficient to maintain growth of all newly formed zygotes. We tested this possibility by altering the vegetative source to reproductive sink ratio in the inbred line A188 prior to imposing a water deficit at pollination. Relative assimilate supply was modified by growing plants in 20-L pots containing 22 kg of amended soil in three environments: (i) the field, (ii) the field under 55% shade, or (iii) a growth chamber. Sink size was modified genetically using a chromosome interchange (reciprocal translocation) mutant (T3-7c) that is nearisogenic to the wild type (A188WT) but sets only 50% of the fertilized ovaries. Six treatment-genotype combinations produced a seven-fold range in photosynthesis per kernel and a four-fold range in reserve sugars per kernel at silk emergence. Water was withheld on the first day silks emerged and plants were hand pollinated 4 to 7 d later when leaf photosynthesis was <2 pmol m-2 s-1 and silk water potential (Tw) reached =-1.1 MPa. Upon rehydration 2 d after pollination (DAP), leaf Tw and photosynthesis rapidly recovered to control values. The water deficit decreased kernel number per ear 40 to 70% compared to the controls. Plants with a high source/sink ratio (e.g., T3-7c, field) were just as sensitive to low Tw at pollination as plants with a low source/ sink ratio (e.g., A188WT, growth chamber). These results indicate that assimilate supply per kernel alone does not determine the sensitivity of kernel set to low Tw at pollination.

Modeling of corn yield in Brazil as a function of meteorological conditions and technological level

“…The definition of sowing dates can greatly influence productivity results, as drought affects yield differently depending on crop stage (Zinselmeier et al, 1995;Yan et al, 2016). In the state of Goiás, for example, the regular sowing period lasts typically for nearly 60 days, from mid-October to mid-December, with the highest concentration in the center of the period (mid-November).…”

“…Drought also causes induced infertility and kernel abortion or shriveled grain, which can strongly reduce harvest index. That's why crop stages from tasseling to beginning of grain filling are critical for corn yield (Zinselmeier et al, 1995).…”

Low Water Potential Disrupts Carbohydrate Metabolism in Maize (Zea mays L.) Ovaries

“…Hydrolysis of Suc by wall-bound invertase is thought to maintain a favorable SUC gradient and cell turgor for rapid phloem unloading (Shannon et al, 1986). Accumulation of Suc in the pedicel at low I/Iw may explain why it has not been possible to improve seed set in water-deficient plants by increasing the amount of carbohydrate reserves prior to silk emergence (Schussler and Westgate, 1994;Zinselmeier et al, 1994 is a major sink for assimilates d u r i n g anthesis (Edmeades and Daynard, 1979;Setter and Meller, 1984;Zinselmeier, 1991) a n d remains a strong sink even a t low +w Westgate, 1991, 1994;Zinselmeier, 1991). Boyle et al (1991) have shown that it is possible to overcome the lack of assimilate movement t o the ovaries and recover approximately 70% of the kernel loss at low +w by infusing a large amount of Suc (>4 g d-') into the stem of water-deficient plants prior to pollination.…”

Deficit hídrico e produtividade na cultura do milho

“…Por outro lado, se o deficit hídrico ocorrer no período crítico, ou seja, da pré-floração ao início do enchimento de grãos (Morizet & Togola, 1984), a recuperação da capacidade produtiva da cultura não poderá ocorrer de forma satisfatória, uma vez que os eventos reprodutivos são muito mais rápidos do que os verificados durante o crescimento vegetativo. Nessa etapa fenológica, o milho é extremamente sensível ao deficit hídrico, em decorrência dos processos fisiológicos ligados à formação do zigoto e início do enchimento de grãos (Shussler & Westgate, 1991;Zinselmeier et al, 1995), além da elevada transpiração, decorrente da máxima área foliar e da elevada carga energética proveniente da radiação solar.…”