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Photosynthetic abilities, light response, and stomatal function in six agroforestry species, Dipterocarpusÿtuberculatus, D.ÿalatus, Eucalyptusÿcamaldulensis, Heveaÿbrasiliensis, Colocasiaÿgigantea, and C.ÿesculenta in responses to water deficit

KwankhaoÿCha-um^a, SirikornÿSangjun^a, KunyaponÿPrawetchayodom^a, SukanyaÿKlomklaeng^a, SuriyanÿCha-um^b,*

 
ABSTRACT:     We investigated the physiological and morphological responses in six agroforestry tree species Dipterocarpus tuberculatus, D.ÿalatus, Eucalyptus camaldulensis, Hevea brasiliensis, Colocasia gigantea, C.ÿesculenta under limited water availability. Withholding water resulted in reduced field capacity by 71%, 86%, and 48% in D.ÿalatus, D.ÿtuberculatus, and E.ÿcamaldulensis, respectively, resulting in wilting, leaf chlorosis, and leaf burn, respectively. Stomatal density varied among the plant species (1.4–6.2 stomata per 0.0625ÿmm²) and was unaffected by water regimes, whereas stomatal conductance (g_s), transpiration rate (E), and water use efficiency were reduced when plants were subjected to water deficit conditions. Generally, intracellular CO₂ of well-watered plants was not always maintained across increasing light intensity flux (PAR_i), although for E.ÿcamaldulensis this was not the case, as both well-watered and water deficit groups showed a reduction with increasing PAR_i. Net photosynthetic rate was significantly increased in well-watered plants as compared to water stressed plants, depending on the degree of PAR_i. In addition, a positive relation between g_s and E in each plant was demonstrated.

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* Corresponding author, E-mail: suriyanc@biotec.or.th

Received 22 Jun 2017, Accepted 20 Jul 2018