Báo cáo lâm nghiệp: "Variations in seed and seedling responses to water stress in three provenances of Eucalyptus camaldulensis Dehnh"

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Nội dung Text: Báo cáo lâm nghiệp: "Variations in seed and seedling responses to water stress in three provenances of Eucalyptus camaldulensis Dehnh"

Variations in seed and seedling responses to water stress in three provenances of Eucalyptus camaldulen- sis Dehnh. A. Gibson E.P. Bachelard Department of Forestry, Australian National University, Canberra, :tralia UE A those used previously (Gibson and Bachelard, Introduction 1987). The initial establishment (hypocotyl raised, cotyledons opened) of seedlings from germinated seeds placed on the surface of soils Previous work (Bachelard, 1985, 1986a, at different moist:ure contents (35, 18 and 10%, b; Gibson and Bachelard, 1987; Yang et w/w) in containers in a controlled environment al., 1988) has shown that seeds and seed- cabinet was observed, and early seedling lings of eucalypt species, subspecies and growth measured. Effects of water stress (10% provenances within a species may differ in s.m.c. for 6 wk) on tissue-water relations, water use efficiency, partitioning of dry matter into their germination and growth responses to roots, stems and leaves, leaf growth and mor- water stress. Seeds from 3 provenances phology were also determined in 8 wk old seed- of Eucalyptus camaldulensis Dehnh. dif- lings grown in pots in a glasshouse with and fered in their abilities to germinate under without added fertiliser. different atmospheric vapour pressure deficits (VPD) and plate matric potentials in a manner consistent with the moisture Results conditions in the environment in which these provenances occur naturally (Gib- son and Bachelard, 1987). In this study, Establishment and early seedling growth the effects of water stress on the initial establishment and early growth of seed- established from most seeds Seedlings lings from 3 provenances of E. camaldu- the surface of soils at 35% sown on lensis were examined. s.m.c., with slightly fewer Katherine seed- establishing (Table I). Fewer seed- lings established from seeds sown on d 2 lings Materials and Methods due to the drying of the soil surface between d 1 and 2. At 18% s.m.c., Petford seedlings established best and The 3 provenances of E. camaldulensis (Kathe- Katherine seedlings worst. These dif- rine and Petford from monsoonal sites; Tennant ferences in establishment were associated Creek from a semi-arid site) were the same as
with differences between provenances in to the soil and assist early seedling firmly uptake. Shoot growth of Petford the production of hairs on the collar of ger- water minating seedlings (Fig. 1which bind the seedlings was best at high s.m.c. but, at low s.m.c., the few Tennant Creek seed- III lings whose radicle penetrated the soil grew best (Fig. 2). of older Response seedlings to water stress Osmotic potentials of seedlings from all provenances were lowered similarly (by 0.1-0.3 MPa) by water and nutrient stress. Water use efficiency as measured directly
(g Dwt/kg water) and by carbon discrimi- Both water and nutrient stress caused nation the leaves to become more linear (as analysis (Farquhar and Richards, opposed to lanceolate) in shape. Principal 1984) was significantly largest in water- stressed, fertilised Tennant Creek seed- component analysis (Cooley and Lohnes, lings (Fig. 3). Water stress reduced leaf area most in - [L 1) TII ICr-r--. , Katherine seedlings (Fig. 4), and the prov- enances also differed in stress-induced changes in the partitioning of dry matter into roots, stems and leaves (Fig. 5). Stressed Tennant Creek seedlings allo- cated more dry matter into leaves at the expense of roots, whereas the reverse situation prevailed in seedlings from the other 2 provenances. The proportion of dry matter distributed to stems was consistently lowest in Tennant Creek seedlings.
Seeds from the monsoonal Katherine provenance showed the least ability to germinate and its seedlings the least ability to establish, in dry environments. Petford seeds established best in dry environments and, although fewer Ten- nant Creek seedlings established, those which did establish and whose radicle penetrated the soil, grew best. Leaf areas were reduced most by water stress in Katherine seedlings. Stressed Tennant Creek seedlings maintained a higher proportion of dry weight in leaves and least in stems and, in fertilised seed- lings, those from Tennant Creek had the highest water use efficiency. The change to a linear leaf form which is associated 1971) of the ratios of the width of a leaf to with more arid conditions in provenances length at several positions along its length of E. camaldulensis (Andrew, 1973) was shows that Tennant Creek seedlings as- greatest in stressed Tennant Creek seed- sumed the most linear leaf shape (most lings. negative in Fig. 6). Leaf shape was af- The responses of Petford seedlings fected most by nutrient stress in Tennant this is, like interesting, although were as Creek and Petford seedlings, and by Katherine, from a monsoonal environ- water stress in Katherine seedlings. ment, its responses were intermediate between Tennant Creek and Katherine and, in several instances, it appeared the Discussion and Conclusions most adaptable provenance. It occurs naturally on well-drained, sandy, infertile The results indicate that the 3 prove- soils and is developing a reputation as an nances of E. camaldulensis differ in their outstandingly successful provenance in adaptations to specific environments. many plantations outside Australia. Speci- ETFORD KATHERINE NT A TENN CREEK
References Andrew LA. (1973) Variation in leaf morphology among provenances of Eucalyptus camaldu- lensis Dehnh. grown in Rhodesia. Rhod. J. Agric. Res. 11, 1 155-169 Bachelard E.P. (1985) Effects of soil moisture stress on the growth of seedlings of three euca- lypt species. I. Seed germination. Aust For. Res. 15, 103-1144 Bachelard E.P. ( 1986a) Effects of soil moisture on the growth of seedlings of three euca- stress lypt species. 11. Growth effects. Aust For. Res. 16, 51-61 Bachelard E.P. (’1986b) Effects of soil moisture stress on the growth of seedlings of three euca- lypt species. 111. Tissue-water relations. Aust For. Res. 1 6, 1 55,-1 63 Cooley W.E. & Lohnes P.R. (1971) In: Multi- variate Data Analysis. John Wiley & Sons, New York Farquhar G.D. & Richards R.A. (1984) Isotopic composition of plant carbon correlates with water-use efficiency of wheat genotypes. Aust J. Plant Physiol. 11, 539-552 Gibson A. & Bachelard E.P. (1987) Provenance variation in germination response to water stress of seeds of some eucalypt species. fic adaptations to their environment may Aust. For. Res. 17,49-58 have important consequences for the suc- Yang D., Bachel2ird E.P. & Banks J.C.G. (1988) cess of species and provenances within a Growth and water relations of of two seedlings species in plantations in alien environ- of Tree subspecies Eucalyptus globulus. Phy- ments. siol. 4, 129-138