Ear Rachis Xylem Occlusion and Associated Loss in Hydraulic Conductance Coincide with the End of Grain Filling for Wheat

Abstract

Seed dehydration is the normal terminal event in the development of orthodox seeds and is physiologically related to the cessation of grain dry mass accumulation and crop grain yield. For a better understanding of grain dehydration, we evaluated the hypothesis that hydraulic conductance of the ear decreases during the latter stages of development and that this decrease results from disruption or occlusion of xylem conduits. Whole ear, rachis, and stem nodes hydraulic conductance and percentage loss of xylem conductivity were measured from flowering to harvest-ripeness on bread wheat (Triticum aestivum L.) cv. Récital grown under controlled environments. Flag leaf transpiration, stomatal conductance, chlorophyll content and grain and ear water potentials were also measured during grain development. We show that grain dehydration was not related with whole plant physiology and leaf senescence, but closely correlated with the hydraulic properties of the xylem conduits irrigating the grains. Indeed, there was a substantial decrease in rachis hydraulic conductance at the onset of the grain dehydration phase. This hydraulic impairment was not caused by the presence of air embolism in xylem conduits of the stem internodes or rachis but by the occlusion of the xylem lumens by polysaccharides (pectins and callose). Our results demonstrate that xylem hydraulics plays a key role during grain maturation.

A Mobile NMR Sensor and Relaxometric Method to Non-destructively Monitor Water and Dry Matter Content in Plants

“…The wheat experiment demonstrates how NMR sensing can be used to monitor seed filling and dry matter accumulation in the living plant (Figures 6, 7). Many studies presented data on the development of FW, DW and WC during seed filling in wheat (Brenchley and Hall, 1909;Schnyder and Baum, 1992;Altenbach et al, 2003;Yang et al, 2004;Pepler et al, 2006;Xie et al, 2015;Neghliz et al, 2016;Zhang et al, 2017) or on seed filling in general (Kermode and Finch-Savage, 2002), but all used destructive methods. The pattern of development in FW, DW, and WC that we measured (Figure 6) matches well with these studies, but were obtained non-destructively and with a much higher time resolution: 4 min per data point, continuously, vs. only a single data point per day, in the daytime, for most other studies.…”

Exploring the Hydraulic Failure Hypothesis of Esca Leaf Symptom Formation

“…Two-to 2.5-mm-thick transverse sections were cut using an Ultracut S microtome (Reichert) equipped with a glass knife. As described by Neghliz et al (2016), the cross section was stained with different dyes. To investigate anatomical features, lignin, phenolic compound, and polysaccharide cross sections were stained with 0.05% (w/v) Toluidine Blue O.…”

Delaying or Delivering: Identification of novel NAM-1 alleles which delay senescence to extend grain fill duration of wheat

“…Differences in grain fill between staygreen lines and cv. Paragon occur towards the end of the rapid grain filling phase, which Neghliz et al . (2016) estimates to occur 39 daa for Triticum aestivum cv.…”