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Effects of Precipitation, Air Temperature and Drought on Calyx Lobe Number of Peganum nigellastrum Bge (Peganaceae Van Tieghem)

Narantsetseg Amartuvshin
Institute of Botany, Mongolian Academy of Sciences, Ulaanbaatar-21051, Mongolia,

Abstract

Calyx lobe number on the fi rst fl owers of Peganum nigellastrum was 3-5 in the desert-steppe and 5 in the forest-steppe, but it decreased on the next fl owers down to 2 or completely disappeared in the desert-steppe, and up to 3-4 in the forest-steppe. The average of 4.4-7.6 mm of precipitation and 11-13oC temperature of 10 days could be adequate for calyx maturity. Calyx could grow for at least 11 days after rainfall and decreasing mean of air temperature. The calyx on the fi rst fl owers rapidly grew, compared with that of the next fl owers. Maturity rate of calyx on the next fl owers was inhibited under drought. Calyx maturity on the fi rst fl owers may be completed, using an underground storage of previous year, but calyx on the next fl owers may be grown, using only photosynthetic production. Dryness that continued up to 11 days can call increased calyx lobe number of P. nigellastrum, and dryness that continues for longer than 11 days calls the decreased calyx lobe number.

Keyword: Peganum nigellastrum,calyx lobe number,dryness,precipitation,air temperature

Introduction

Drought affects on plant productivity, growth and morphology (Ivanov et al., 2004; Fraser et al, 2009; Jean-Marcel Ribaut et al., 2009), as well as on cellular (Voronin et al., 2003) and subcellular metabolism levels (Zelling et al., 2004). This effect can be estimated by biomorphological changes of above ground biomass of dominant plants (Adar et al, 2006). The effects of precipitation, temperature (Voronin et al., 2003; Fraser et al., 2009) and drought (Ivanov et al., 2004; Ribaut et al., 2009) on leaf morphology have been described, but the effects of precipitation, temperature and drought on calyx lobe number are still unclear. Peganum nigellastrum Bge belongs to the family Peganaceae Van Tieghem, and is adapted in the desert and desert-steppe (Shiirevdamba, 1990; Tserenkhand, 1999; Ivanov et al., 2004). This species is distinguished from other taxa of the genus by calyx leaves incised into 5-7 lobes, hispid and stolon (Bobrov, 1949; Grubov, 1982, 1998). Stolon of this species found in most regions of Mongolia, such as Khangai, Mongol- Daurian, Middle Khalkh, Depression of Great Lakes, Valley of Lakes, Gobi Altai, East Gobi, Alasha Gobi, but calyx are entire or incised into 2-7 lobes. Calyx lobe number of this species may increase or decrease under different ecological factors. The purpose of this study was to describe whether precipitation and air temperature and drought affects on the calyx lobe number of P. nigellastrum and to explain mechanisms of calyx lobe number range.

Material and Methods

Calyx lobes of P. nigellastrum were sampled and counted in Dalanzadgad (N43o57’48”; E104o43’20”, elev. 1461 m) and Mandalgobi cities (N45o76’08”; E106o27’62”, elev. 1418 m) are located in the desert-steppe zone, and Altanbulag town (N50o31’84”; E106o48’94”, elev. 690 m) in the forest-steppe zone in 2008. Air temperature in each locality is gradually increased during growing season of P. nigellastrum, according to the data of Institute of Metereology and Hydrology. The average air temperature in Dalanzadgad was higher than in other localities. Maximum air temperature was from July 6 to July 10, 2008 in Dalanzadgad, whereas it was between June 6 and June 10 in Mandalgobi, and between June 25 and June 30 in Altanbulag (Fig. 1). Amount of precipitation by 5 days was different among the localities. Total amount of precipitation was 25.3, 54.4 and 149.3 mm in Dalanzadgad, Mandalgobi and Altanbulag, respectively. The highest amount of precipitation in Dalanzadgad was from June 26 to June 30, whereas in Mandalgobi it was high between July 6 and July 10, and between June 21 and June 25 in Altanbulag (Fig. 1). The frequency distribution of annual precipitation is calculated in the range (World Meteorological Organization, 1975):

where, P is decade amount of precipitation from April to mid July, Paver – long term average of precipitation, stdp - the standard deviation of 10 day precipitation, from late April to mid July.


According to the criteria, the extreme dry condition in Dalanzadgad was continued during fl owering season of P. nigellastrum. The extreme dry condition in Mandalgobi was from May 1 to June 30 and normal condition was in the fi rst ten days of July. Dryness in Altanbulag was the lowest than in other localities. The extreme dry condition in Altanbulag occurred in the fi rst and second ten days of May and June, and normal condition was in the third ten days of May and June. Persistent calyx lobe number of P. nigellastrum did not change during the peak fl owering and fruiting stages. Calyx of P. nigellastrum was collected near roads, from 15 to 20 day intervals. When calyx leaves are collected, they were distinguished by the fl ower location on the stem. Lobes were counted on 100 calyx leaves, for each location. Differences of calyx lobe number were estimated by geographical, the fl ower locality on the stem and among the fi rst, second, third and fourth fl owers, using Mann-Whithney U-test (Avery, 2004). Also, correspondences among calyx lobe number and days after precipitation and the mean of 10 days’ air temperature were estimated by Spearman rank correlation (rs) and between calyx lobe number and dryness were by ANOVA, using JMP 4.0.

Result

Calyx with 3 lobes dominantly occurred on upper side of stem in Dalanzadgad and Mandalgobi, while calyx with 3-4 lobes occurred in Altanbulag. The calyx with 3-5 lobes occurred near base of stem in Dalanzadgad and Mandalgobi, whereas calyx with 5 lobes dominantly occurred in Altanbulag (Fig. 2). Difference of calyx lobe number between fl owers, where near base and upper side of stems were found in the early June in Dalanzadgad and Mandalgobi, but in late June in Altanbulag. Calyx lobe number in Altanbulag was more than in other localities, but no difference found between Dalanzadgad and Mandalgobi, except for late June. In early June, calyx with 3 lobes dominantly occurred on upper side of stem in Dalanzadgad and Mandalgobi, while that with 5 lobes occurred in Altanbulag. The calyx with 5 lobes was dominated near base of stem in Altanbulag, but 3-5 lobes recorded in other regions. In late June, calyx with 3 lobes dominantly occurred on upper side of stem in Dalanzadgad and Mandalgobi, while 3-4 lobes occurred in Altanbulag (Fig. 3, Tab. 1). In Dalanzadgad, calyx with 5 lobes dominated on the fi rst fl owers, whereas calyx lobe number decreased on the second and third fl owers (Fig. 4A, Tab. 2). In Mandalgobi, the calyx with 3-5 lobes dominated on the fi rst fl owers, but the lobe number decreased down to 3 on the second and third fl owers. The calyx lobe number on the fourth fl owers was the fewest (Fig. 4B, Tab. 2). In Altanbulag, the calyx with 5 lobes dominated on the fi rst and second fl owers, but the calyx lobe number decreased to 3 on the third fl owers (Fig. 4C, Tab. 2). Relation between calyx lobe number and precipitation showed that maturity of calyx with 5 lobes was intense after 4.4-7.7 mm of precipitation, but the calyx with 5 lobes decreased when precipitation is less than 4.4 or more than 7.6 mm; the maturity of calyx with 3 lobes was intense after 0.8-7 mm of precipitation, whereas of the calyx with 3 lobes decreased when more than 7 mm of precipitation. The correspondence between the calyx lobe number and mean of 10 days’ air temperature illustrated that maturity of calyx with 5 lobes was intense when air temperature fl uctuated between 11 to 13oC, whereas it was decreased when more than 13oC; the maturity of calyx with 3 lobes was intense when temperature is 19-21oC, but it was decreased when temperature extends above or below this range. Calyx with 2-4 lobes or without lobe was found for 1-6 days after precipitation, whereas lobe number increased up to 5 for 7-11 days after precipitation (Fig. 5A). The calyx with 3-5 lobes was occurred when the mean of 10 days’ air temperature was 11-16oC, whereas lobe number decreased to 2 or even lobes disappeared when temperature ranged between 19 and 21oC (Fig. 5B). Calyx lobe number on the second fl owers in the forest-steppe zone was similar with that of fi rst fl owers. The calyx lobe number on the fi rst fl owers of P. nigellastrum was more than on the next fl owers because of calyx on the fi rst fl owers can grow better in spring season. The decrease of calyx lobe number on the second (excluding in the forest steppe), third and fourth fl owers can show that maturity rate of calyx on these fl owers inhibited under drought.



Relation between calyx lobe number and day number after precipitation and air temperature show that calyx of P. nigellastrum could completely grow for at least 11 days after rain, when decreased mean air temperature. The precipitation of 4.4-7.6 mm and temperature of 11oC-13oC are to be adequate for calyx maturity of P. nigellastrum. Calyx maturity in the foreststeppe could be completed for 10 days after an adequate rain, with suffi cient air temperature, but in the desert-steppe it could be for 8-11 days after insuffi cient rain.



It means that the calyx maturity in the desert-steppe could be completed, using an underground storage. The dryness in the desert-steppe was stronger than in the forest steppe and then calyx lobe number in the desert-steppe decreased signifi cantly. The frequency distribution of annual precipitation (WMO, 1975) has considered for dryness. Calyx with 3-5 lobes was dominantly occurred when dry condition continued for 10-40 days, while only 3 lobes were found when drought extended for 50- 70 days. The calyx with 2 or without lobe was recorded with more than 70 days of drought. Relationship between calyx lobe number and days after precipitations (Fig. 5A) and duration of dry condition (Fig. 6) show that different factors affected either increase or decrease of the calyx lobe number. The results can illustrate that decrease of calyx lobe number are related with drought, because of calyx growth was inhibited under continuously dryness. Decrease of calyx lobe number on the third fl owers in the forest-steppe was insignifi cant than in the desert-steppe, resulting suffi cient precipitation in the foreststeppe, which makes better condition than desert-steppe. Calyx on the second (excluding in Altanbulag) third and fourth fl owers may be grown, using only photosynthetic production. In addition to decrease of calyx lobe number, the drought calls a reduced leaf area, especially in the upper part of the plant, as increased the erect leaves and leaf thickness (Voronin et al., 2003; Ivanov et al., 2004; Fraser et al., 2009; Ribaut et al., 2009). Adar et al. (2001) discussed about drought level estimation, using bio-morphological data (such as plant and change of leaf color and shape, leaf fall) of dominant plants of Mongolian Gobi. Geographic difference of calyx lobe number of P. nigellastrum shows that dryness in Dalanzadgad and Mandalgobi was stronger than in Altanbulag, up to early June. It was progressive in Mandalgobi up to late June. Calyx lobe number was 3-5 in the desertsteppe and 5 in the forest steppe between May 20 and May 30 but it decreased to 3 in the desertsteppe and no decrease occurred in the forest steppe between June 1 and June 10 because of drought in the forest steppe began later than in the desert-steppe. Infl orescence near base of stems begins earlier than of upper side of stems and then calyx lobe number of fl owers near base of stems can indicate dryness up to early June whereas that of fl owers upper of stems indicates up to late June.




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