Guedira, Mohammed

Paulsen, Gary M.

Shroyer, James P.

Kansas State University

Kansas Agricultural Experiment Station Research Reports Volume 0 Issue 12 Keeping up with Research Article 56 1985 Growth and Survival of Wheat Seedlings After Dehydration and Rehydration Mohammed Guedira James P. Shroyer Gary M. Paulsen This report is brought to you for free and open access by New Prairie Press. It has been accepted for inclusion in Kansas Agricultural Experiment Station Research Reports by an authorized administrator of New Prairie Press. Copyright 1985 Kansas State University Agricultural Experiment Station and Cooperative Extension Service. Contents of this publication may be freely reproduced for educational purposes. All other rights reserved. Brand names appearing in this publication are for product identification purposes only. No endorsement is intended, nor is criticism implied of similar products not mentioned. K-State Research and Extension is an equal opportunity provider and employer. Follow this and additional works at: https://newprairiepress.org/kaesrr Recommended Citation Guedira, Mohammed; Shroyer, James P.; and Paulsen, Gary M. (1985) "Growth and Survival of Wheat Seedlings After Dehydration and Rehydration," Kansas Agricultural Experiment Station Research Reports: Vol. 0: Iss. 12. https://doi.org/10.4148/2378-5977.7293 Growth and Survival of Wheat Seedlings After Dehydration and Rehydration Keywords Keeping up with research; 87 (Sept. 1985); Kansas Agricultural Experiment Station contribution; no. 86-72-S; Wheat seedlings; Dehydration; Rehydration; Seedlings; Planting depth Creative Commons License This work is licensed under a Creative Commons Attribution 4.0 License. This research report is available in Kansas Agricultural Experiment Station Research Reports: https://newprairiepress.org/kaesrr/vol0/iss12/56 GROWTH AND SURVIVALOF WHEAT SEEDLINGSAFTER DEHYDRATIONAND REHYDRATIONMohammed Guedira, James P. Shroyer,and Gary M. Paulsen*The planting depth of wheat often is increased toplace the seeds in damp soil when low surface mois-ture restricts germination and seedling development.However, planting seed deeply in dry soil oftenresults in low emergence, slow seedling development,and thin stands. Even if moisture is adequate for ger-mination of seeds, continued lack of precipitationmight dehydrate seedlings and stop their growth untiladditional rain occurs to rehydrate them. The abilityof seedlings to tolerate dehydration/rehydration isimportant for establishing stands of wheat. In addi-tion, planting deeply and delaying emergencedepletes carbohydrate reserves in the endospermthat are needed by the seedlings. This study wasdesigned to determine the ability of wheat seedlings,especially the coleoptile and root, to withstand desic-cation and the effect of the stress at different devel-opmental stages on seedling emergence. A fullaccount of the study was published in AgronomyJournal 89:822-826 (1997).ProceduresSeedling Development after Dehydrationand Rehydration. We used seeds of Larned, a tall,hard red winter wheat cultivar with a long coleoptile.Similarly sized seeds ranging from 5/64 to 7/64 inchin diameter were placed on paper towels. The towelsThis publication from the Kansas State University Agricultural Experiment Station and Cooperative Extension Service has been archived. Current information is available from http://www.ksre.ksu.edu.were modified with paper wicks that were immersedin distilled water to maintain saturation and coveredwith aluminum foil to minimize evaporation. Eachtowel held 30 seeds.Towels containing the seeds were kept in darknessin a germination chamber at 77°F and 80% relativehumidity for 1, 2, 3, 4, or 5 d. After germination,seedlings were removed carefully and spread on drytowels to dehydrate. Nongerminated seeds were dis-carded, and the number of seedlings per paper towelwas reduced to 20 by random selection. All manipu-lations were performed in a dark room under a dimgreen safelight.Seedlings were dehydrated for 1, 2, 3, 4, or 5 d inthe darkened growth chamber set at 77°F and 60%relative humidity. The developmental stage of theseedlings at the onset of dehydration is shown inTable 1. After the dehydration treatment, seedlingswere rehydrated on moistened paper towels by theprocedure used for germination until the first true leafappeared.Seedling development after rehydration was deter-mined daily by changes in coleoptile and rootlengths. Coleoptile length was measured from thepoint where the seedling ruptured the seed coat tothe tip until elongation ceased. Root length was mea-sured by spreading the roots over grid squares andcounting the number of intercepts of roots with hor-izontal and vertical grid lines. The grid dimension was0.2 inch; root length was the number of interceptstimes 0.3206. Weight of the seed remnants in eachtreatment combination was measured after seedlingswere dehydrated as an indication of endospermreserve utilization. Samples of 10 seedlings eachwere air dried and weighed.Experiments were arranged in a completely ran-domized block design with three replications of eachtreatment combination. Data were analyzed statisti-cally by the general linear model method.Seed l ing  Emergence  a f t er  Dehydrat ion .Seeds that germinated for 1, 2, 3, or 4 d and weredehydrated for 2 d as described above and nonger-minated seeds (0-d controls) were planted at sixdepths (1, 2, 3, 4, 5, and 6 inches) in vermiculite.Containers 20 inches long, 14 inches wide, and8 inches high were used. Seeds and seedlings werein rows 14 inches long and 4 inches apart with25 entries per row. The vermiculite was moistenedwith distilled water, and transparent covers wereplaced on the containers to prevent evaporation.Containers were held in environmental chambersmaintained at 77°F during the 16-hr day and 60°Fduring the 8-hr night with 450 µmol m -2s-1 lightingduring daytime.Seedling emergence, defined as penetration of thecoleoptile through the vermiculate surface, was mea-sured daily. Seedling vigor was evaluated by an emer-gence rate index, which was calculated as the sum ofdaily observations of the number of emerged seed-lings divided by the number of days from planting.A split plot design with three replications wasused. Planting depths were main plots, and days ofgermination were subplots in single rows. Analysis ofvariance was used to examine effects of days of ger-mination before dehydration and seeding depth.Least significant differences at the 0.05 probabilitylevel were calculated to detect differences inemergence.Results and DiscussionSeedling Development after Dehydrationand Rehydration Survival was high after seedlingsgerminated for up to 3 d and were dehydrated for1 to 3 d and then rehydrated (Fig. 1). After 4 d ofgermination, however, seedlings were increasinglysusceptible to longer periods of dehydration.Seedling survival declined from 60% after 3 d ofdehydration to zero after 5 d of dehydration.Seedlings that germinated for 5 d were highly sus-ceptible to all but the l-d dehydration treatment.Average maximum coleoptile length at the end ofthe rehydration period was affected more by durationof germination than duration of dehydration (Fig. 2).The coleoptile lengths of seedlings from seeds thatgerminated for 1 d were reduced to about 80% of thelength of coleoptiles of control seedlings and did notdiffer among dehydration treatments. Longer periodsof germination greatly reduced coleoptile growthafter dehydration and rehydration. Most of thecoleoptile length after 3 d of germination was pre-sent before the dehydration treatment. Little or noelongation occurred after seedlings were dehydratedand rehydrated.The mean rate of coleoptile elongation followinggermination, dehydration, and rehydration reflectedthe change in coleoptile length (data not shown).Growth was rapid after 1 d of germination butdecreased progressively as the germination periodlengthened to 2, 3, and 4 d. Prolonged dehydrationhad little effect after only 1 d of germination, but itprogressively decreased the rate of elongation after2, 3, or 4 d of germination.Dehydration after germination also greatlyaffected the survival and growth of roots (data notshown). Seedlings that germinated for 1 d retainedthe original seminal roots, which recovered from alldehydration treatments. For seedlings that germi-nated longer than 1 d, new roots replaced the origi-This publication from the Kansas State University Agricultural Experiment Station and Cooperative Extension Service has been archived. Current information is available from http://www.ksre.ksu.edu.nal ones, which did not survive dehydration.Maximum root length decreased more than maxi-mum coleoptile length as the days of germinationincreased. Extending the period of dehydration hadlittle effect on seedlings that germinated for 1 or 2 d.But for seedlings that germinated for 3, 4, or 5 d,dehydration was increasingly detrimental to rootgrowth. Few roots were produced after 5 d of germi-nation, even with the l-d dehydration treatment.The weight of the seed remnants changed littleduring germination for 1 or 2 d but then decreasedrapidly until the fifth day, when is leveled off (Fig. 3).Changes in the dry weight of seeds during germina-tion undoubtedly reflected loss of carbohydrates andproteins from the endosperm for growth and respi-ration of the seedlings. Reserves of these constituentswere depleted quickly to low levels during the latestages of germination.Seed l ing  Emergence  a f t er  Dehydrat ion .Emergence of seedlings from vermiculite illustratedthe adverse effects of advanced stages of germinationon stand establishment after dehydration and rehy-dration. Germination for 1 to 3 d followed by dehy-dration for 2 d had little effect on emergence ofseedlings from shallow planting (Fig. 4A). As plantingdepth increased, however, all germination periodslonger than 1 d followed by 2 d of dehydrationreduced seeding emergence. Germination for 1 dincreased the emergence rate of seedlings froml- and 2-inch depths relative to nongerminated con-trol seeds (Fig. 4B). Germination for longer periodsfollowed by 2 d of dehydration decreased the emer-gence rate index as the planting depth increased. Thefew seedlings that emerged after germination for 3 or4 d, dehydration, and planting 3 inches or deeperwere chlorotic and soon died. When seedlings did notemerge, their coleoptile stopped growing, and thefirst true leaf often developed below the soil surface.Table 1. Development of Larned wheat seedlingsafter 1 to 5 d of germination.Days of ColeoptileGermination LengthRootLengthRootNumberNote: Measurements were taken immediately beforeseedlings were subjected to dehydration treatments.Figure 1. Mean survival of seedlings from wheatseeds that germinated for 1 to 5 d, were dehy-drated for 1 to 5 d, and then were rehydrated.Control seedlings were not dehydrated. Vertical baris LSD (0.05)=15.5.Figure 2. Maximum coleoptile length of seedlingsfrom wheat seeds that germinated for 1 to 5 d,were dehydrated for 1 to 5 d, and then were rehy-drated. Control seedlings were not dehydrated.Vertical bar is LSD (0.05)=0.30.This publication from the Kansas State University Agricultural Experiment Station and Cooperative Extension Service has been archived. Current information is available from http://www.ksre.ksu.edu.ConclusionsWheat seedlings that have germinated for 1 to 3 dmight survive drying out and rehydration by rainand produce a stand. Seedlings at advanced stagesof germination might not survive even milddehydration.Figure 3. Mean dry weight of remnants of wheatseeds that germinated for 1 to 6 d. Vertical bar isLSD (0.05)=0.013.Dehydration shortens the coleoptile of wheatseedlings and reduces emergence from deepplanting. Seed should not be planted deeper than80% of the maximum coleoptile length of non-stressed seedlings.Dehydration injures roots as severely as shoots andmight hinder establishment and survival ofseedlings even if they emerge.Poor survival and growth after dehydration andrehydration of seedlings at advanced stages oftodevelopment are related to loss of tolerancedesiccation and depletion of seed reserves.Figure 4 .  Mean percentage emergence (A)  andemergence rate index (B) of wheat seedlings fromnongerminated seeds (0-d controls) and seeds thatgerminated for 1 to 4 d, were dehydrated for 2 d,p l a n t e d  1  t o  6  i n c h e s  d e e p ,  a n d  r e h y d r a t e d .Vertical bars are LSD (0.05)=14.5(A) and 0.50(B).This publication from the Kansas State University Agricultural Experiment Station and Cooperative Extension Service has been archived. Current information is available from http://www.ksre.ksu.edu.*Graduate Research Assistant and Professors, respectively,Department of AgronomyContribution no. 98-286-S from the Kansas AgriculturalExperiment Station.Contents of this publication may be freely reproduced foreducational purposes. All other rights reserved. In eachcase, give credit to the author(s), name of work, KansasState University, and the date the work was published.Kansas State University Agricultural Experiment Station andCooperative Extension Service, Manhattan, Kansas 66506SRL 119 March 1998It is the policy of Kansas State University Agricultural Experiment Station andCooperative Extension Service that all persons shall have equal opportunity andaccess to its educational programs, services, activities, and materials without regard torace, color, religion, national origin, sex, age, disability, or other nonmerit reasons.Kansas State University is an Affirmative Action employer. These materials may beavailable in alternative formats. 1MThis publication from the Kansas State University Agricultural Experiment Station and Cooperative Extension Service has been archived. Current information is available from http://www.ksre.ksu.edu.

Growth and Survival of Wheat Seedlings After Dehydration and Rehydration (1998)

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Growth and Survival of Wheat Seedlings After Dehydration and Rehydration (1985)

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