RELATIONSHIP BETWEEN MORPHOLOGICAL AND PHYSI- OLOGICAL ATTRIBUTES OF HOP HORNBEAM SEEDLINGS

Most commonly used morphological attributes were correlated with nutrient concentration in order to standardize quality assessment of two-year-old hop hornbeam (Ostrya carpinifolia Scop.) seedlings. Diameter has proven to be the best single morphological indicator of seedling quality given its strong positive correlation with all other observed morphological attributes. Seedling dry mass (shoot and root dry mass) and Dickson Quality Index can be considered the most comprehensive indicators of hop hornbeam seedling quality. However, the measuring of mass is destructive and requires a certain amount of time. The absence of strong correlations between physiological and morphological attributes of two-year old seedlings of hop hornbeam suggests the need for further research. The only significant correlation between physiological and morphological attributes (weak and positive) was recorded between the potassium concentration in root and root collar diameter after the second growing season.


INTRODUCTION
Assessment of seedling quality is more important for afforestation planning than for the pricing of seedlings.Further, during the selection of methods and interpretation of the results of seedling quality testing, assessment of performance should be clearly separated from the assessment of field survival (G r o s s n i c k l e , Fo l k , 1993).The choice of parameters to measure when assessing seedling quality, in addition to the use of results should be based on the efficiency in terms of time, cost and destructiveness of the chosen method.The measuring of dry mass of seedlings and the mass of individual parts of fresh plants is certainly destructive.In addition, the measurement of most parameters of root development is destructive and time consuming.The measuring of height and root collar diameter is quick, easy and non-destructive.However, used individually, these parameters are not sufficient to assess seedling quality (H a a s e , 2008).Because of that, many derived indicators have been proposed, such as sturdiness quotient (R o l l e r, 1977) which includes height and diameter or quality index (D i c k s o n et al., 1960), which includes height and diameter combined with biomass.G r o s s n i c k l e and Fo l k (1993) reported that the measurement of four variables (diameter, height, shoot water potential at planting and root growth capacity) is sufficient to evaluate the morphological and physiological condition of seedlings.
The analysis of nutrient concentration for the assessment of seedling quality has been mainly focused on nitrogen, phosphorus and potassium, or stored nutrients, usually in the form of sugars and starches (M a t t s s o n , 1996).
In Serbia, there are no certified seed sources of hop hornbeam (Iv e t i ć et al., 2010), as well as organized production of reproductive material, despite recommendations by many authors on its use as the main or associated species in a number of sites (J o v i ć et al., 1998(J o v i ć et al., , I s a j e v et al., 2006(J o v i ć et al., , 2010(J o v i ć et al., , To m i ć et al., 2011)).Testing of the relationship between different morphological attributes, as well as between nutrient concentrations, will contribute to the defining of the quality standards of this and other species.

MATERIAL AND METHOD OF RESEARCH
The fruit was harvested immediately after maturation, at three sites northeast of Gazivodsko Lake.The fruit was dried in a thin layer at room temperature.After drying, the seed was extracted by thrashing in small sacks, and then separated from the mixture by wind blowing.In order to break dormancy, the seed was stratified in moist sand at a temperature of 0° to 5° C for 140 days.The stratified seeds were sown in large containers in a mixture of sand and peat with the 2: 1 ratio.The first germinants appeared on the fifth day after sowing.By the end of the growing season, manual weeding was performed every four weeks.Irrigation was performed at least twice a week.After the first growing season, 945 seedlings were transplanted into three seedbeds (315 per seedbed).During the second growing season, manual weeding was performed every 15 days.
Before transplanting, all 945 one-year-old seedlings were measured for height (H 1 ), root collar diameter (D 1 ) and the number of developed buds (NBd).After the second growing season, all seedlings were measured for height (H 2 ), root collar diameter (D 2 ), number of branches (NBr) and dry mass, as total seedling mass (Msd), shoot mass (Msh) and root mass (Mro).Seedling dry mass was measured after drying the plant material in the thermostat cabinet at a temperature of 68 ° C for 48 hours.
The quality index (QI) was calculated (D i c k s o n et al., 1960) from the measured morphological parameters after the second growing season: Concentration of nitrogen, phosphorus and potassium in shoots and roots was measured at the end of the second growing season.Sample preparation for the determination of P and K was performed using wet combustion of plant material in nitric acid and hydrogen peroxide.From the obtained extract, phosphorus was determined colorimetric with the use tin chloride and ammonium molybdate.Potassium was determined by flame photometry.Nitrogen content was determined by the Kjeldahl method.
The relationship between individual morphological attributes and physiological attributes of the seedlings was measured by simple linear correlation (Pearson R).The correlation coefficients were calculated in the statistical program STATISTICA 7.

DISCUSSION
The examination of the relationship between the measured morphological and physiological attributes showed a strong positive correlation between all morphological attributes.As expected, H 1 showed the strongest positive correlation with H 2 .In addition, H 1 showed a strong positive correlation with Msh and Msd, measured after the second growing season.H 2 showed the strongest positive correlation with Msh, as previously reported for the wild cherry (S t j e p a n o v i ć , Iv e t i ć , 2013).These strong correlations of height and shoot mass are consistent with seedling structure.According to M a t t s s o n (1996), correlation between the initial height and success after planting in the field is often contradictory, while diameter is a useful indicator of survival and growth after planting in the field.Height is a reliable indicator of seedling quality only when used combined with the diameter.J a c o b s et al. (2005) found significant positive correlation between height, diameter, root volume and fresh mass with height and diameter of red oak seedlings in the first and second year after planting in the field.
There is a strong positive correlation between D 1 and D 2 with all other measured morphological attributes, except with the Nbd and Nbr.Significant correlation between diameter and shoot and root was reported by R u e h l e and K o r m a n i k (1986) for red oak seedlings.B i n o t t o et al. (2010) reported that the root collar diameter is the best single indicator of seedling quality, given its high-level correlation with the quality index.S t j e p a n o v i ć and Iv e t i ć (2013) also reported on the high level of correlation between the diameter and the quality index.Diameter is a good indicator of root development, such as volume and dry mass (J a c o b s et al., 2004, S t j e p a n o v i ć , Iv e t i ć , 2013).It seems that the correlation between the diameter and height grows stronger with age because the correlation between D 2 and H 2 is much stronger compared to the correlation between D 1 and H 1 .
Dry masses of seedling, shoot and root expected, showed the strongest correlation with each other.In addition, all masses show a very strong correlation with QI.
QI showed the strongest correlation with dry masses (Msd, Msh, Mro), which is consistent with the results reported by B i n o t t o et al. (2010), and expected considering the calculation method.
In the case of physiological attributes, a weak positive correlation was recorded between the nutrient concentration in shoot and root; as well as between Pr and Kr.On the other hand, a negative correlation was recorded between Ps with Ks and Kr.Mattsson (1996) states that despite the extensive literature on nutrient concentration in seedlings, there is no extensive research on their correlation with their success on the field and the results are often contradictory.He also states that nitrogen concentration in the leaves has a certain potential as a predictor of seedling growth after planting in the field.On the other hand, the results obtained in this research indicate a lack of significant correlation between nitrogen concentration in shoot and root, with all measured morphological attributes.Even if it is not significant, there is a negative correlation between Ns with all measured morphological attributes.
The only significant correlation between physiological and morphological parameters (weak and positive) was recorded between Kr and D 2 .
The results from this research confirm the statements of a number of authors about the correlations among the morphological attributes of seedling quality (T h o m p s o n , 1985, R o l l e r, 1976, H a a s e , 2007, Iv e t i ć , 2013, S t j e p a n o v i ć , Iv e t i ć 2013).

CONCLUSION
The diameter has proven to be the best single morphological indicator of hop hornbeam seedling quality, given its strong correlation with other measured morphological attributes.Seedling height should be used only when combined with the diameter.Assessment based on height is reliable only for shoot development, given the strong correlation with dry mass.However, height is important, because it can refer to seedling survival and success in the field, especially in weedy habitats.
Seedling dry mass (shoot and root mass) and quality index represent the most comprehensive indicators of hop hornbeam seedling quality, but the measuring of mass is destructive and requires a certain amount of time.

Table 1 .
. Correlation coefficients between the morphological attributes: height after the first (H 1 ) and second (H 2 ) growing seasons, diameter after the first (D 1 ) and second (D 2 ) growing seasons, number of buds (NBd), number of branches (NBr), total dry mass (Msd), shoot dry mass (Msh), root dry mass (Mro) and quality index (QI) Табела 1. Коефицијенти корелације између морфолошких показатеља: висине након прве (H 1 ) и друге (H 2 ) gгодине, пречника након прве (D 1 ) и друге (D 2 ) године, броја пупољака (NBd), броја грана (NBr), масе садница у сувом стању (Msd), масе изданка у сувом стању (Msh), масе корена у сувом стању (Mro) и индекса квалитета (QI) + . . . . . . . . . . . . . . . . . . . . . . . .(1) 1 shows strong correlation with H 2 , as well as with Msh and Msd.D 1 shows a very strong correlation with D 2 , as well as with other measured morphological attributes, except with Nbd and Nbr.Nbd shows very strong correlation with Nbr.H 2 shows very strong correlation with Msh, Msd and D 2 , and moderate correlation with Nbd and Nbr.The strongest correlation of D 2 is with D 1 , but is very strong with all the other measured morphological attributes, except with Nbd and Nbr.Interestingly, D 2 shows moderate correlation with H 1 , but very strong correlation with H 2 .In addition to very strong correlation with Nbd, Nbr shows a moderate correlation with other measured morphological attributes.As expected, Msd showed an extremely strong correlation with Msh, and a very strong correlation with Mro and QI and a moderate correlation with Nbd and Nbr.Except the extremely strong correlation with Msd, Msh shows a very strong correlation with Mro and QI.Mro shows a very strong correlation with Msd, Msh and QI and strong correlation with H 1 .QI shows a very strong correlation with Mro, Msd and Msh and moderate correlations with Nbd, Nbr (0.5941) and H 1 , figure 1.

Table 2 .
Correlation coefficients between nitrogen concentration in shoot (Ns) and root (Nr),