Activities of starch synthetic enzymes and contents of endogenous hormones in waxy maize grains subjected to post-silking water deficit

Abstract

Rainfed maize in Southern China and frequently suffer water deficit at later plant growth periods. A pot trial in 2014–2015 was conducted to study the effects of drought stress (the relative soil moisture contents are 70–80% and 50–60% under control and water deficit conditions, respectively) after pollination on grain filling and starch accumulation, activities of starch synthetic enzymes, and contents of indole-3-acetic acid (IAA) and abscisic acid (ABA), with Suyunuo5 as test material. The grain fresh weight, volume, and dry weight were not affected by drought before 10 days after pollination but were restricted thereafter. The reduction at maturity was reduced by 33.3%, 40.0%, and 32.3% in 2014 and by 21.7%, 24.3%, and 18.3% in 2015. The grain filling rate was suppressed by water deficit, whereas grain moisture and starch content were slightly affected. The starch accumulation was decreased by 33.5% and 20.0% at maturity in 2014 and 2015, respectively. The activities of starch synthetic enzymes (sucrose phosphate synthase, sucrose synthase, ADP-glucose pyrophosphorylase, soluble starch synthase, and starch branching enzyme) were downregulated by post-silking drought. The ABA content was increased, whereas IAA content was decreased when plants suffered water deficit during grain filling. In conclusion, post-silking water deficit increased ABA content, decreased IAA content, and weakened the activities of starch synthetic enzymes, which suppressed grain development and ultimately reduced grain weight.

Application of Exogenous Phytohormones at Silking Stage Improve Grain Quality under Post-Silking Drought Stress in Waxy Maize

“…Similar results were observed in fresh waxy maize [ 32 ], normal maize [ 34 ], barley [ 35 ], and wheat [ 9 ]. The decrease may be due to downregulated enzymatic activities related to starch synthesis and decreased IAA content [ 31 ]. Grain weight was unaffected by exogenous phytohormones under control conditions in both hybrids.…”

“…In YN7, starch content with GA or BR was unaffected by drought, but the value with CTK or water decreased ( Figure 2 ). Drought reduced grain starch content [ 5 , 6 , 7 ], owing to down-regulated enzymatic activities related to starch biosynthesis [ 31 , 40 ]. The decreased starch content under drought condition without phytohormones may be due to enlarged starch granules, which cannot compensated the reduced numbers of starch granules [ 11 ].…”

“…Drought is the main environmental stress in China. Previous studies reported that grain yield and starch quality are affected by post-silking water deficit, which restricts starch deposition, downregulates enzymatic activities related to starch synthesis, reduces the sizes of starch granules, decreases starch crystallinity, and shortens amylopectin chains [ 31 , 32 , 33 ]. However, little is known about the influence of exogenous phytohormones on maize grain quality under drought stress.…”

Identification and Expression of NAC Transcription Factors of Vaccinium corymbosum L. in Response to Drought Stress

“…Actually, a similar phenomenon has also been reported in other species. In maize (Zea mays), ABA content increased significantly under water deficit, whereas IAA content noticeably decreased [57]. In adonis (Adonis amurensis), ABA content increased continuously as the duration of drought stress advanced, whereas the content of GA decreased in plants [26].…”

Comparison of Selection Traits for Effective Popcorn (Zea mays L. var. Everta) Breeding Under Water Limiting Conditions

“…However, in 2016, where the water limitation occurred later, the main effect was noticed in 100GW (but not for the variables related to grain quantity), which also affected GY. Water stress may shorten the period of grain filling, decrease photosynthetic activity, accelerate ABA-mediated leaf senescence and reduce the activity of enzymes involved in sucrose metabolism and starch synthesis, which altogether can contribute to a lower grain weight ( Yang and Zhang, 2006 ; Sehgal et al., 2018 ; Yang et al., 2019 ).…”