Photosynthetic behaviour during the leaf ontogeny of rubber tree clones[Hevea brasiliensis (Wild. ex. Adr. de Juss.) Muell. Arg.], in Lavras, MG

Abstract

This work proposed to investigate changes in the photosynthetic behavior during the leaf ontogeny of the during the leaf development. Up to the 32nd day of leaf age (stage B2), the net photosynthesis was negative due to the inefficiency of the photosynthetic system, and this fact was justified by the following factors: low chlorophyll content, less stomatal conductance, high rubber tree clones PB 235, RRIM 600 and GT 1, in Lavras, MG. The experiment was performed in 2004, between May and July, under field conditions, at the Universidade Federal de Lavras. During the leaf ontogeny, the following characteristics were evaluated: chlorophyll content, gaseous exchanges and chlorophyll fluorescence. The clones presented similar profiles of alterations in the physiological characteristics internal CO2 levels and low chlorophyll fluorescence. From the 37th day of leaf age, net photosynthesis became positive and gradually higher, stimulated by the increases in the chlorophyll contents, photochemical efficiency of photosystem II, carboxylation efficiency, stomatal conductance, transpiration and water use efficiency. Among the clones, photosynthetic behavior was similar, reaching maximum performance on the 57th day of leaf age (stage D), when clone RRIM 600 showed the highest net photosynthesis, differing from the clones PB 235 and GT 1.

Desenvolvimento inicial de clones IAC de seringueira em São José do Rio Preto, SP

“…(MIGUEL et al, 2007), sendo que os lançamentos maduros são as fontes disponíveis para suprir a demanda fotossintética dos demais drenos. Nessa variável biométrica, também se observa menor desempenho do IAC 301 com relação à testemunha, mas não com relação aos demais clones IAC.…”

Perkembangan Ontogenetik Daun Tanaman Karet Sebagai Penanda Awal Adaptasi Terhadap Cekaman Lingkungan Dan Patogen

“…Beberapa penelitian telah dilakukan terutama untuk mengetahui perubahan fisiologis daun (Miguel et al, 2007) dan efek lingkungan (Vinod et al, 2010 …”

“…(Miguel et al, 2007;Vinod et al, 2010) Miguel et al (2007) Selama ini perkembangan stadia daun umumnya dinyatakan dalam bentuk kualitatif berdasarkan fisual terutama warna daun seperti daun tembaga, daun hijau muda, dan daun tua. Pembedaan stadia daun dalam beberapa fase yaitu A, B, C dan D yang digunakan oleh para ilmuan nampaknya dapat juga menjadi standar dalam menjelaskan stadia perkembangan daun dalam praktik di lapangan.…”

“…Penelitian Miguel et al (2007) menunjukkan bahwa peningkatan signifikan kadar klorofil a,b, dan total klorofil pada fase A sampai fase B2, selanjutnya terjadi penurunan pada fase C kemudian meningkat secara signifikan pada fase D (Gambar 1a). Penurunan klorofil a,b, dan total klorofil antara fase B2 dan C terjadi bersamaan dengan laju ekspansi daun yang tinggi.…”

“…Miguel et al (2007) Secara fisiologis fase A, B dan C bersifat sink (Lieberei, 2007) dengan proses pemanjangan dan multiplikasi sel yang cepat (Vinod et al, 2010), sedangkan fase D merupakan source yang telah memiliki karakteristik fisiologis dan struktural daun dewasa (Lieberei, 2007). Hasil penelitian Miguel et al (2007) menunjukkan bahwa fotosintesis bersih pada fase B2 negatif, mulai positif pada fase C dan terus meningkat seiring pertambahan umur daun (Gambar 1b). Daun berperan sebagai sink yang kuat dan menggunakan cadangan fotosintat pada fase A sampai B2.…”